ima

Passport 7400, 15000, 20000

Inverse Multiplexing forATM Guide

241-5701-730

Passport 7400, 15000, 20000

Inverse Multiplexing for ATM Guide

Publication: 241-5701-730Document status: StandardDocument version: 5.1S1Document date: March 2003

Copyright © 2003 Nortel Networks.All Rights Reserved.

Printed in Canada

NORTEL, NORTEL NETWORKS, the globemark design, the NORTEL NETWORKS corporatelogo, PASSPORT, and DPN are trademarks of Nortel Networks.VT100 is a trademark of Digital Equipment Corporation.

5

00,

Publication history

March 20035.1S1 StandardGeneral availability. Contains information on Passport 7400, Passport 150and Passport 20000 for the PCR5.1 GA release.

Passport 7400, 15000, 20000 Inverse Multiplexing for ATM Guide 5.1S1

6 Publication history

241-5701-730 5.1S1

7

Contents

About this document 13Who should read this document and why 13What you need to know 14How this document is organized 14What’s new in this document 14

IMA scalability 15Text conventions 15Related documents 16How to get more help 17

Chapter 1IMA overview 19What is IMA? 19How does IMA work? 20Network implementations of IMA 21Terminology specific to IMA 23Supported ATM features and services on Passport 23Function processors supporting IMA 25IMA link groups and independent links 27

Provisioning configurations for the eight-port DS1/E1 ATM functionprocessors 28

Provisioning configurations for the 32-port DS1/E1 MultiserviceAccess function processors 28

Provisioning configurations for the four-port DS3Ch ATM functionprocessor 30

IMA protocols 30Applicability 30


8 Contents

ATM Forum IMA protocol 31Proprietary IMA protocol 31

Bandwidth options using ATM 31IMA link group capacity on the eight-port DS1/E1 ATM FPs 32IMA link group capacity on the 32-port DS1/E1 Multiservice Access

FPs 33IMA link group capacity on the four-port DS3Ch ATM FP 33

Chapter 2IMA feature description 35IMA in the ATM layer reference model 36Cell transport functionality using IMA 37IMA framing and control 42

ICP cell distribution 42ICP cell contents 44Cell rate decoupling using filler cells 47

Link capacity within an IMA link group 47IMA link states 47Internal procedures for IMA link configuration 48Adding inactive links to an IMA link group 48

After the startup procedure 49When the IMA link group is functioning 49After the link addition and reactivation procedure 50

Compensating for asynchronous physical links 50Transmit clock mode 52

Common transmit clock (CTC) mode 53Independent transmit clock (ITC) mode 54Guidelines for transmit clock mode 55

Compensating for differential delay 56Using cell buffers to maintain link delay synchronization 56Measuring differential delay during IMA link group startup 57Ongoing monitoring of differential delay 57Link selection criteria 58

ATM IMA service reliability on Passport 15000 for SuccessionNetworks 60

ATM control channel failure on IMA 62

241-5701-730 5.1S1

Contents 9

Chapter 3Configuring IMA 63Prerequisites to configuring IMA 64MSA32 configuration pre-requisites 65IMA and the ATM interface 65IMA components and configurable attributes 66IMA configuring links 68Notes about configuring IMA 71Mixed configurations 72

Example of a mixed configuration without traffic shaping 74Example of a mixed configuration with traffic shaping 75

Configuring IMA link groups and independent links 77Configuring the Passport FP supporting the IMA feature 77Configuring the ports, IMA link groups, and independent links 79Configuring the ATM interface and linking it to an IMA link group or

an independent link 84Migrating software releases 86Upgrading IMA groups to the ATM Forum IMA protocol 87

Upgrading an existing IMA link group on the eight-port DS1/E1 ATMFPs 87

Re-configuring the IMA software features list 88

Chapter 4IMA feature monitoring 89How to monitor services and features on Passport 90OSI management states 90IMA components and operational attributes 91Internal diagnostics 93

Locking and unlocking a port component 93Locking and unlocking an IMA component 94

Maintenance tests 95Performing a manual test on the IMA component 95Port tests 99

Monitoring the status of the IMA application 99Monitoring the status of a Link 100

Determining the status of an IMA link 100


10 Contents

Determining the status of all links in an IMA group based onstatistical attributes 101

Determining the cause of the most recent OIF anomaly 102Determining the number of one-second intervals in which idle cells

were received 102Determining if the IMA group is active 103Determining the active links in an IMA group 105

Determining the active and failed links in an IMA group 105Determining which links in the IMA group are currently active and

configured at the remote end 106Monitoring IMA capacity and utilization 107

Determining the throughput available over an IMA group 108Determining the current cell utilization of an IMA group 108

Monitoring relative link delays 109Determining remote link configuration 110Determining if the IMA group provides adequate bandwidth 111

Chapter 5Troubleshooting IMA 113Passport alarms 113IMA-specific alarms 115

IMA group alarms 115IMA link alarms 117

Link alarms for the proprietary IMA protocol 117Link alarms for the ATM Forum IMA protocol 117

The troubleshooting process 118Tools for troubleshooting IMA 118Troubleshooting using Nortel Networks Preside Multiservice Data

Manager 118Handling problems 119

AppendixPassport IMA compliance to specification 131

241-5701-730 5.1S1

Contents 11


List of figures

Figure 1 The concept of inverse multiplexing (unidirectionalexample) illustrated using the eight-port DS1/E1 ATMFP 20

Figure 2 Example of using IMA link groups (Passport 7400) in anATM network 22

Figure 3 IMA in the ATM layer reference model 37Figure 4 An IMA link group between two eight-port DS1/E1 ATM

FPs supporting IMA (Passport 7400) 38Figure 5 IMA link groups between two four-port DS3Ch ATM FPs

supporting IMA (Passport 15000 or 20000) 39Figure 6 Detailed view of multiple IMA link groups between two

eight-port DS1/E1 ATM FPs (Passport 7400) 40Figure 7 Detailed view of multiple IMA link groups and

independent links forming in a four-port DS3Ch ATM FP(Passport 15000 or 20000) 41

Figure 8 Example of IMA framing and ICP cell distribution on alink group 43

Figure 9 Contents of an ATM Forum IMA protocol ICP cell on allPassport 7400, 15000, 20000 FPs supporting IMA 45

Figure 10 Contents of a proprietary IMA protocol ICP cell on theeight-port DS1/E1 ATM FPs supporting IMA 46

Figure 11 Example of cell stuffing to preserve the order of cellsover links running at different speeds 51

Figure 12 Measuring differential delay over links in an IMA linkgroup 58

Figure 13 Example of an IMA link group illustrating different linkselection criteria 60

Figure 14 IMA feature components and configurable attributes 67Figure 15 Component hierarchy showing examples of configuring

links required for IMA using the eight-port E1 ATM FP(Passport 7400) 70

Figure 16 Example of a mixed configuration without traffic shapingon the eight-port E1 ATM FP (Passport 7400) 74

Figure 17 Example of a mixed configuration with traffic shapingenabled on the eight-port E1 ATM FP(Passport 7400) 76

Figure 18 IMA feature components and operational attributes 92Figure 19 Example of an IMA alarm appearing on the text

interface 114

12 Contents

241-5701-730 5.1S1

List of tables

Table 1 IMA and related Passport features 24Table 2 Passport function processors supporting IMA 25Table 3 Where to find information on the Passport FPs that

support IMA 26Table 4 Method of transferring ATM layer cell traffic between

function processors 32Table 5 Transmit clock mode supported by the different IMA

protocols on Passport 52Table 6 Where to find information on ATM connection types that

can be transported over an IMA link group onPassport 7400, Passport 15000 and 20000 66

Table 7 Handling problems 119Table 8 Passport IMA mandatory specification compliance 132Table 9 Passport IMA optional specification compliance 134

13

for

About this document

The purpose of 241-5701-730Passport 7400, 15000, 20000 InverseMultiplexing for ATM Guideis to provide customers with information on theinverse multiplexing for ATM (IMA) feature available on Passport.

• “Who should read this document and why” (page 13)

• “What you need to know” (page 14)

• “How this document is organized” (page 14)

• “What’s new in this document” (page 14)

• “Text conventions” (page 15)

• “Related documents” (page 16)

• “How to get more help” (page 17)

Who should read this document and whyThis document is for persons working on Passport’s inverse multiplexingATM feature. It is specifically written for persons who perform the followingtasks with a Passport IMA application:

• installing and configuring

• provisioning

• operating and maintaining

• troubleshooting


14 About this document

e

linert

What you need to knowYou need to have a basic understanding of the following:

• how ATM functions on Passport

See 241-5701-700Passport 7400, 15000, 20000 ATM Overview.

• how to configure and monitor ports

— 241-7401-200Passport 7400 Hardware Description

— 241-1501-200Passport 15000, 20000 Hardware Description

— 241-7401-240Passport 7400 Hardware Installation, Maintenanceand Upgrade

— 241-1501-210Passport 15000, 20000 Hardware Installation Guid

— 241-5701-600Passport 7400, 15000, 20000 Configuration Guide

— 241-5701-050Passport 7400, 15000, 20000 Commands

• how to configure and monitor a Passport node using the command interface or Preside Multiservice Data Manager architect for Passpo

See 241-6001-023Preside MDM Configuration Management forPassport User Guide.

How this document is organizedThe 241-5701-730Passport 7400, 15000, 20000 Inverse Multiplexing forATM Guide contains the following sections:

• “IMA overview” (page 19)

• “IMA feature description” (page 35)

• “Configuring IMA” (page 63)

• “IMA feature monitoring” (page 89)

• “Troubleshooting IMA” (page 113)

What’s new in this documentThe following feature was added to this document:

• “IMA scalability” (page 15)

241-5701-730 5.1S1

About this document 15

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ype

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IMA scalabilityThis feature increases the number of ports that support IMA on MSA FPfrom:.

• 24 to 30 ports on the DS1 MSA FP

• 22 to 28 ports on the E1 MSA FP

The section “Provisioning configurations for the 32-port DS1/E1Multiservice Access function processors” (page 28) was updated.

Text conventionsThis document uses the following text conventions:

• nonproportional spaced plain type

Nonproportional spaced plain type represents system generated textext that appears on your screen.

• nonproportional spaced bold type

Nonproportional spaced bold type represents words that you should tor that you should select on the screen.

• italics

Statements that appear in italics in a procedure explain the results oparticular step and appear immediately following the step.

Words that appear in italics in text are for naming.

• [optional_parameter ]

Words in square brackets represent optional parameters. The commcan be entered with or without the words in the square brackets.

• <general_term >

Words in angle brackets represent variables which are to be replacedspecific values.



h thees)

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ted

rting( / )int,

),

de

• UPPERCASE, lowercase

Passport commands are not case-sensitive and do not have to matccommands and parameters exactly as shown in this document, withexception of string options values (for example, file and directory namand string attribute values.

• |

This symbol separates items from which you may select one; forexample, ON|OFF indicates that you may specify ON or OFF. If you dnot make a choice, a default ON is assumed.

• ...

Three dots in a command indicate that the parameter may be repeamore than once in succession.

The term absolute pathname refers to the full specification of a path stafrom the root directory. Absolute pathnames always begin with the slashsymbol. A relative pathname takes the current directory as its starting poand starts with any alphanumeric character (other than /).

Related documentsIn addition to the documents listed in “What you need to know” (page 14see the following documents for related information:

• 241-5701-005Passport 7400, 15000, 20000 List of Terms

• 241-5701-030Passport 7400, 15000, 20000 Overview

• 241-5701-030Passport 7400, 15000, 20000 Overview

• 241-5701-270Passport 7400, 15000, 20000 Software Installation Gui

• 241-5701-600Passport 7400, 15000, 20000 Configuration Guide

• 241-5701-060Passport 7400, 15000, 20000 Components

• 241-5701-420Passport 7400, 15000, 20000 Trunking Guide

• 241-5701-500Passport 6400, 7400, 15000, 20000 Alarms

241-5701-730 5.1S1

About this document 17

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the

• 241-5701-702Passport 7400, 15000, 20000 ATM Routing and SignalinFundamentals

• 241-5701-705Passport 7400, 15000, 20000 ATM Traffic ManagemenFundamentals

• 241-5701-706Passport 7400, 15000, 20000 ATM Traffic Shaping andPolicing

• 241-5701-707Passport 7400, 15000, 20000 ATM Queuing andScheduling

• 241-5701-708Passport 7400, 15000, 20000 ATM CAC and BandwidManagement

The following documents provide additional information on inversemultiplexing for ATM:

• ATM Forum AF-PHY-0086.000,Inverse Multiplexing for ATM (IMA)Specification, Version 1.0.

Note:When this specification is referred to throughout the rest of thidocument, it is assumed that the version is Version 1.0, unless otherwstated.

• ATM Forum AF-PHY/95-1121R5,Inverse Multiplexing for ATM (IMA)Specification, Baseline Text, October 1996.

How to get more helpFor information on training, problem reporting, and technical support, see“Nortel Networks support services” section in the product overviewdocument.



241-5701-730 5.1S1

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Chapter 1IMA overview

This chapter provides an overview of inverse multiplexing for ATM (IMA) onPassport and includes the following:

• “What is IMA?” (page 19)

• “How does IMA work?” (page 20)

• “Network implementations of IMA” (page 21)

• “Terminology specific to IMA” (page 23)

• “Supported ATM features and services on Passport” (page 23)

• “Function processors supporting IMA” (page 25)

• “IMA link groups and independent links” (page 27)

• “IMA protocols” (page 30)

• “Bandwidth options using ATM” (page 31)

What is IMA?Inverse multiplexing for asynchronous transfer mode (ATM), or IMA, is afeature available on Passport that supports the transparent transmissionATM cell data over an IMA link group. Depending upon the functionprocessor in use, IMA transparently distributes a single stream of ATM laycell traffic onto one (four-port DS3Ch ATM FP) or more (eight-port DS1/EATM FP, 32-port DS1/E1 Multiservice Access FP) physical links fortransmission across the links. IMA then combines the traffic back into thoriginal ATM layer cell sequence at the remote end.


20 Chapter 1 IMA overview

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How does IMA work?IMA groups multiple DS1 or E1 physical links or logical links (depending othe type of function processor) to form a single high-speed ATM link. Thlink is called an IMA link group. The figure “The concept of inversemultiplexing (unidirectional example) illustrated using the eight-port DS1/EATM FP” (page 20) shows an example of two Passport 7400 nodes withfunction processors (FPs) running IMA. In this example, eight DS1 or E1lines are grouped together to form one IMA link group.

The number of IMA link groups and the number of DS1 or E1 physical linkor logical links forming the IMA link groups are determined by the particulaPassport function processors and by the provisioning decisions. See “Ctransport functionality using IMA” (page 37) for details on the IMAimplementation on Passport.

Figure 1The concept of inverse multiplexing (unidirectional example) illustratedusing the eight-port DS1/E1 ATM FP

Passport A(with FP running IMA)

Passport B(with FP running IMA)

ATM interface ATM interface

Example:cell traffic from Passport A to Passport B

cell stream isinverse multiplexed

cells transmitted overmultiple physical links

cells over links combined intooriginal cell stream

direction of cell flow

241-5701-730 5.1S1

Chapter 1 IMA overview 21

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Network implementations of IMAAn IMA link group can be used in various network implementations. Forexample, an IMA link group can be used within a Passport network, or toaccess an external ATM network.

The figure “Example of using IMA link groups (Passport 7400) in an ATMnetwork” (page 22) shows an example of how an IMA link group can be usto provide higher speed links between access and backbone layer switchIn this example, the link group speed is three times the E1 rate, or 5.715 Ms. The ATM Forum protocol is being used, in this case, by the Passport nin the access layer. This allows interoperability with the external vendorequipment in the backbone layer, based on the ATM ForumInverseMultiplexing for ATM (IMA) Specification.

On Passport 7400, IMA can also be used to provide high speed accessbetween backbone switches at rates between E1 and E3. In this examplelink group speed is five times the E1 rate, or 9.525 Mbit/s. One of the beneof IMA is that existing hardware can be used to access higher line rates

Note: It is possible to transport an IMA cell stream over a bit transparemedium, such as leased DS1/E1 lines or the AAL1 circuit emulationsystem supported on Passport. However, due to the format requiredIMA control protocol (ICP) cells, it is not possible to transport the IMAcell stream over an ATM network between nodes running ATM beareservice (cell relay). For details on ICP cells, see “IMA framing andcontrol” (page 42).



Figure 2Example of using IMA link groups (Passport 7400) in an ATM network

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241-5701-730 5.1S1


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Terminology specific to IMAInverse multiplexing for ATM refers to the transparent transport of a singleATM cell stream over one or more physical links, and the combining andreordering of cells back into the original stream at the receiving end.

An IMA link group refers to the combination of one or more physical orlogical links (depending on the type of function processor) that use the invemultiplexing process to transmit traffic across these links. (This may alsoreferred to as anIMA group.) An IMA link group is presented as a single linkto the ATM layer. A link group originates on one FP running the IMA featurand terminates on another FP running the IMA feature (typically these Fare on two different Passport nodes).

Channelization refers to a function processor’s ability to group DS1 accesonto a DS3 line. On Passport 15000 and 20000’s DS3 channelized ATM28 individual DS1 channels (lines or ATM UNIs) are multiplexed anddemultiplexed on each of four DS3 cell streams (112 DS1 channels or 1ATM UNIs).

An independent linkrefers to a single DS1/E1 physical link (eight-port DS1E1 ATM FP, 32-port DS1/E1 Multiservice Access FP) or DS1 logical link(four-port DS3Ch ATM FP) that is used directly by the ATM layer, withoubeing part of an IMA link group.

Note:An IMA link group is capable of using the IMA protocol over asingle DS1/E1 physical link or DS1 logical link (depending of the typof function processor). This is useful when the current requirement monly warrant the use of a single physical link or logical link, butanticipated growth will require additional links. Physical or logical linkcan be added to the IMA link group as the need for additional bandwidarises.

Supported ATM features and services on PassportIMA accommodates cell level ATM layer traffic and is compatible with thfull range of associated Passport ATM features. IMA supports fully integratPassport functionality, including

• ATM traffic management for different service categories within an ATMinterface



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• Passport routing system for the efficient handling of link failures

The following table shows additional features that closely interwork withIMA on Passport. These features are described elsewhere in the Passpdocumentation suite.

IMA fully supports the orderly and predictable allocation of bandwidthwithin a link group using ATM quality of service as outlined in the existintraffic management contract. For more information see the followingdocuments:



Table 1IMA and related Passport features

Feature Document with featuredescription

Feature description

Inverse multiplexing forATM

241-5701-730 Passport7400, 15000, 20000Inverse Multiplexing forATM Guide

Describes IMA feature, benefits,functionality, provisioning, monitoring,troubleshooting

Core services’connection bandwidthcontrol (CBC)

241-5701-700 Passport7400, 15000, 20000 ATMOverview

Describes how the CBC algorithm controlsthe response of different ATM connectionsthat are part of an ATM interface to achange in bandwidth over an IMA linkgroup

Dynamic trunk speedchanges

241-5701-420 Passport7400, 15000, 20000Trunking Guide

Describes the speed changes on ATMtrunks required to maintain a direct logicaltrunk connection on a permanent singlehop PVC when a bandwidth change occurson an IMA link group

Point-to-multipointconnections

241-5701-700 Passport7400, 15000, 20000 ATMOverview

Describes CBC requirements for point-to-multipoint connections

241-5701-730 5.1S1


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• 241-5701-708Passport 7400, 15000, 20000 ATM CAC and BandwidManagement

IMA supports existing ATM features and services. For example:

• ATM bearer service

• ATM logical trunks (AAL5), including ATM direct adjacent trunks

• Circuit Emulation (AAL1)

• ATM multiprotocol encapsulation (MPE)

• Frame Relay over ATM

IMA includes support for

• Passport services that can be carried over ATM (Services related to votransport, voice networking, and transparent data are supported onPassport 7400, Passport 15000 and 20000.)

• Passport ATM connections such as PVCs, soft PVCs, and SVCs.

Note:These lists of Passport features supported by IMA are notcomprehensive. Features are added in each Passport release.

Function processors supporting IMAThe table “Passport function processors supporting IMA” (page 25) lists tFPs providing IMA functionality.

Table 2Passport function processors supporting IMA

Function processor Product

eight-port DS1 ATM FP Passport 7400

eight-port E1 ATM FP Passport 7400

32-port DS1 Multiservice Access FP Passport 7400

(Sheet 1 of 2)



nd
The following table shows where to locate descriptions of the Passport aFPs in the Passport documentation suite.
32-port E1 Multiservice Access FP Passport 7400

four-port DS3Ch ATM FP Passport 15000 and 20000

Table 3Where to find information on the Passport FPs that support IMA

Documents Description

241-7401-200 Passport 7400Hardware Description

241-1501-200 Passport 15000,20000 Hardware Description

Describes features and general aspects ofthe FP including

• port configuration and clocking

• line rate

• compliances

• faceplates and connectors

• termination panels

• redundancy support

• cabling

241-7401-240 Passport 7400Hardware Installation,Maintenance and Upgrade

241-1501-210 Passport 15000,20000 Hardware InstallationGuide

Provides procedures for installing the FP,cables and termination panel within thecontext of a full Passport node installationprocedure

(Sheet 1 of 2)

Table 2 (continued)Passport function processors supporting IMA

Function processor Product

(Sheet 2 of 2)

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IMA link groups and independent linksThe individual ports on the eight-port DS1/E1 ATM FPs and the 32-port DSE1 Multiservice Access FPs, and the DS1 logical links on the four-portDS3Ch ATM FPs, can be configured for IMA functionality as follows

• IMA links (part of an IMA link group), or

• independent (stand-alone) links

When using independent links, each individual link must be associated wanAtmIf component. When using IMA, oneAtmIf component is defined foreach IMA link group. See “Configuring IMA” (page 63) for details on how toconfigure IMA link groups, and a mixed configuration of IMA link groupsand independent physical links.

Note:Some provisioning rules apply to mixed configurations. See“Mixed configurations” (page 72).

No traffic losses occur with ATM Forum IMA when you add physical orlogical links. In the case of removal of such links, if there is sufficientbandwidth on the remaining links, there will be no traffic loss. Likewise, yocan remove or add physical or logical links without tearing down the linkgroup or the ATM interface being served by the IMA link group. The failurof one physical or logical link has no effect on the remaining links in the IMlink group (if there is sufficient bandwidth on the remaining physical or

241-7401-240 Passport 7400Hardware Installation,Maintenance and Upgrade

241-1501-215 Passport 15000,20000 Hardware MaintenanceGuide

Provides general maintenance and safetyprocedures.

241-5701-600 Passport 7400,15000, 20000 ConfigurationGuide

Provides procedures for configuring FPs

Table 3 (continued)Where to find information on the Passport FPs that support IMA

Documents Description

(Sheet 2 of 2)



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logical links), except that overall throughput is reduced over the IMA linkgroup. In addition, you can engineer an IMA link group such that if a physiclink fails, service over many ATM connections served by the link can bemaintained at a reduced capacity. Specifically, you can designate ATM dirlogical trunks using single hop permanent virtual connections (PVCs) aselastic connections that continue service if the capacity available to theconnection changes due to a change in IMA group capacity. If IMAbandwidth is reduced, you can configure a direct trunk connection to contiat the reduced throughput or be released.

For information on the provisioning configurations for the Passport functiprocessors, see the following sections:

• “Provisioning configurations for the eight-port DS1/E1 ATM functionprocessors” (page 28)

• “Provisioning configurations for the 32-port DS1/E1 MultiserviceAccess function processors” (page 28)

• “Provisioning configurations for the four-port DS3Ch ATM functionprocessor” (page 30)

Provisioning configurations for the eight-port DS1/E1 ATMfunction processors

The eight-port DS1/E1 ATM FPs for Passport 7400 support

• up to eight IMA link groups per FP with each link group servicing aseparate ATM interface

• up to eight physical links per IMA link group

• up to eight independent links per FP

• a mixture of IMA groups and independent links running simultaneouson an FP

Provisioning configurations for the 32-port DS1/E1Multiservice Access function processors

For the purpose of IMA configuration, consider the 32 ports as divided intwo 16-port blocks. The lower port block includes ports 0 through 15, and tupper port block includes ports 16 through 31.

241-5701-730 5.1S1


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Characteristics and special considerations for configuring IMA on MSA3are provided in the following points.

• On the DS1 MSA32 function processors, a maximum of 15 ports canused for IMA in each port block, if the number of IMA link groups onthat port block is 7 or less.

• On the E1 MSA32 function processors, a maximum of 14 ports can used for IMA in each port block, if the number of IMA link groups onthat port block is 7 or less.

• On the DS1 and E1 MSA32 a maximum of 13 ports can be used for IMin each port block, if each IMA port is in its own IMA link group (13ports in 13 groups). Note it is supported but not typical to have singllink IMA groups.

• When IMA is deployed in a port block, other services (for example,frame relay and circuit emulation) should not be used on that port blo

• Each IMA link group may have up to eight ports.

• All ports in an IMA link group must be in the same port block.

• In the lower port block, any combination of ports can be included in IMA link group; the link instance to which each port is associated is the range of 0 through 15.

• In the upper port block, any combination of ports can be included inlink group; the link instance to which each port is associated is in therange of 0 through 15.

• Interoperability with IMA features in Passport Release 5.0 and later supported.

When configuring IMA on 32-port function processors, you can makeconsiderations for the following:

• the number of IMA groups per port block basis

• the number of link groups across the entire function processor regardof port blocks

• the number of IMA groups for DS1 compared to E1



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In general, there are no semantic limits imposed through software andconfiguration checks. That is, Passport will not disallow provisioning 16 IMports per block, but that configuration will not work; some ports will fail. Thnetwork operator must be aware of and follow the above rules, such asmaximum 14 E1 or 15 DS1 IMA ports per port block.

Provisioning configurations for the four-port DS3Ch ATMfunction processor

The four-port DS3Ch ATM FP for Passport 15000 and 20000 supports

• up to four physical links per FP

• up to 28 DS1 logical links per DS3 port

• up to 14 IMA link groups per DS3 port

• up to 56 IMA link groups per channelized FP (14 IMA link groups x 4ports)

• up to 112 independent links (28 DS1 channels for each of the four Dports) per channelized FP

• a mixture of IMA link groups and independent links runningsimultaneously on an FP

IMA protocolsDepending on which Passport release and which function processor in uPassport IMA software supports one or both of the following distinct IMAprotocols:

• ATM Forum IMA protocol

• a proprietary IMA protocol

ApplicabilityFor the eight-port DS1/E1 function processors, Passport supports both tATM Forum IMA and the proprietary IMA protocols. Passport IMA servicerunning on the 32-port DS1/E1 Multiservice Access FP and the four-porDS3Ch ATM FP, support only the ATM Forum IMA protocol.

The two protocols have much in common, such as low level cell processfunctions that are implemented in hardware. As a result, on the applicabPassport releases onwards from releases 4.1 and 4.2, the two protocols

241-5701-730 5.1S1


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be used simultaneously on separate IMA link groups on the same eight-DS1/E1 ATM FP. However, because there are some significant differencbetween the higher level link groups and link state machines for the twoprotocols, they are not interoperable.

ATM Forum IMA protocolThe ATM Forum IMA protocol, supported in Passport release 5.0 andbeyond, provides interoperability with equipment compliant with the ATMForumInverse Multiplexing for ATM (IMA) Specification. Futureenhancements to Passport’s IMA product will be based on the ATM ForuIMA protocol.

If you are using the eight-port DS1/E1 ATM FPs to provide IMA capabilityyou can choose between the ATM Forum IMA protocol or the proprietaryIMA protocol (see “Applicability” (page 30)). When the ATM Forum IMAprotocol is used exclusively on an FP, memory savings are offered compato the proprietary IMA protocol.

All Passport function processors that provide IMA services support the ATForum IMA protocol.

Proprietary IMA protocolFor IMA services running on the eight-port DS1/E1 ATM functionprocessors, the proprietary IMA protocol provides backwards compatibilwith the proprietary IMA protocol available on Passport releases 4.1 and 4The proprietary protocol is closely based on the IMA protocol defined inbaseline text for the ATM ForumInverse Multiplexing for ATM (IMA)Specification. See “Related documents” (page 16) for exact references toATM Forum publications.

There are no enhancements planned for the proprietary IMA protocol. Itintended primarily for backwards compatibility with earlier implementationof IMA on Passport on releases 4.1 and 4.2 on the eight-port DS1/E1 ATfunction processors.

Bandwidth options using ATMPassport’s IMA feature permits the transfer of ATM layer cell traffic betweeFPs as summarized in the table “Method of transferring ATM layer cell trafbetween function processors” (page 32).



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Typically, the FPs are on different Passport nodes. IMA on the eight-porDS1/E1 ATM FPs and the 32-port DS1/E1 Multiservice Access FPs bridgthe gap between the throughput of a DS1/E1 ATM link and a DS3/E3 ATlink. This is useful where DS3/E3 facilities (or those with higher line speedare not available or cannot be justified due to cost or the volume of ATMtraffic.

IMA link group capacity on the eight-port DS1/E1 ATM FPsWith Passport’s IMA feature on the eight-port DS1/E1 ATM FPs, ATM layecell traffic between the FPs can be transferred across one to eight DS1 ophysical links. Bandwidth can be added to (or removed from) IMA linkgroups up to a maximum of eight DS1 or E1 physical links, as per networequirements. For more information, see “Provisioning configurations for teight-port DS1/E1 ATM function processors” (page 28).

IMA technology also greatly increases the number of DS1 or E1 physicalinks that a Passport 7400 node can support. Instead of up to eight ATMinterfaces over eight physical links between nodes, one ATM interface coperate over eight physical links in an IMA link group. If you use four eighport DS1/E1 ATM FPs, then you can operate up to 32 physical links(minimum of four IMA link groups) between two Passport 7400 nodes usiIMA.

Table 4Method of transferring ATM layer cell traffic between function processors

Function processor Product Method

eight-port DS1 ATM FP Passport 7400 multiple DS1 physical links

eight-port E1 ATM FP Passport 7400 multiple E1 physical links

32-port DS1 MultiserviceAccess FP

Passport 7400 multiple DS1 physical links

32-port DS1 MultiserviceAccess FP

Passport 7400 multiple E1 physical links

four-port DS3Ch ATM FP Passport 15000 and20000

multiple DS1 logical links on a DS3channelized interface

241-5701-730 5.1S1


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For information on IMA link group capacity on the eight-port DS1/E1 ATMFPs, contact your Nortel Networks account representative.

IMA link group capacity on the 32-port DS1/E1 MultiserviceAccess FPs

With Passport’s IMA feature on the 32-port DS1/E1 Multiservice Access FPATM layer cell traffic between the FPs can be transferred across all 32 Dor E1 physical links. Bandwidth can be added to (or removed from) IMA lingroups up to a maximum of eight DS1 or E1 physical links, as per networequirements.

Note:These capabilities are subject to specific characteristics. See“Provisioning configurations for the 32-port DS1/E1 MultiserviceAccess function processors” (page 28) for more information.

For more information, see “Provisioning configurations for the 32-port DE1 Multiservice Access function processors” (page 28). For information IMA link group capacity on the 32-port Multiservice Access FP, contact yoNortel Networks account representative.

IMA link group capacity on the four-port DS3Ch ATM FPWith Passport’s IMA feature on the four-port DS3Ch ATM FPs, ATM layecell traffic can be transferred across a maximum of 28 DS1 logical links one DS3 port. For more information, see “Provisioning configurations for tfour-port DS3Ch ATM function processor” (page 30).

For information on IMA link group capacity on the four-port DS3Ch ATMFP, contact your Nortel Networks account representative.



241-5701-730 5.1S1

35

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Chapter 2IMA feature description

This section describes how inverse multiplexing for ATM (IMA) functions oPassport, including the key concepts associated with this feature. Unlesnoted otherwise, the functionality presented in this chapter applies to bothproprietary IMA protocol (supported on Passport 7400 only) and the ATMForum IMA protocol (supported on Passport 7400, Passport 15000 and20000). For more information, see “IMA protocols” (page 30).

This section specifically describes the following aspects of IMA:

• “IMA in the ATM layer reference model” (page 36)

• “Cell transport functionality using IMA” (page 37)

• “IMA framing and control” (page 42)

• “Link capacity within an IMA link group” (page 47)

• “IMA link states” (page 47)

• “Internal procedures for IMA link configuration” (page 48)

• “Adding inactive links to an IMA link group” (page 48)

• “Compensating for asynchronous physical links” (page 50)

• “Transmit clock mode” (page 52)

• “Compensating for differential delay” (page 56)

• “ATM IMA service reliability on Passport 15000 for SuccessionNetworks” (page 60)


36 Chapter 2 IMA feature description

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IMA in the ATM layer reference modelThe figure “IMA in the ATM layer reference model” (page 37) shows howIMA fits into a standard ATM layer reference model. For speed and efficienIMA functionality is accomplished entirely at the physical layer. Thetransmission convergence sublayer handles the interaction between the Alayer and IMA. This sublayer is divided into the IMA specific part and theinterface specific part; these parts interwork with the physical mediumdependent sublayer to perform full IMA functionality.

• IMA specific part (transmission convergence sublayer) - controls theactual inverse multiplexing functionality, such as the distributing andcombining of the ATM cell stream, cell rate decoupling, IMAsynchronization, compensation for differential delay, and physical linmonitoring and control

Note:The process used by IMA to transmit the ATM cell stream istransparent to the ATM layer

• interface specific part (transmission convergence sublayer) - controlsATM-specific functions of the DS1 or E1 or DS3 physical interface, sucas header error control (HEC), cell delineation and cell scrambling/dscrambling

• physical medium dependent sublayer - controls the transmission of don the E1/DS1 or DS3 physical links

IMA specific functionality is performed in a cell processing logic block callethe IMA cell machine, available in FPs that support the IMA feature. TheIMA cell machine

• handles the sequencing of cells when the links are active

• detects any link failures or status changes and reports them to thesoftware

• generates ICP, filler and stuff cells

IMA software configures each individual link in an IMA link group anddetermines those recognized by the IMA application at the far end FP as bpart of that IMA link group.

241-5701-730 5.1S1

Chapter 2 IMA feature description 37

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Figure 3IMA in the ATM layer reference model

Cell transport functionality using IMAThe figures “An IMA link group between two eight-port DS1/E1 ATM FPssupporting IMA (Passport 7400)” (page 38) and “IMA link groups betweetwo four-port DS3Ch ATM FPs supporting IMA (Passport 15000 or 20000(page 39), illustrate the concept of inverse multiplexing. In each figure, arunning IMA in Passport A receives a single stream of cell traffic from thATM layer and transparently distributes the individual cells in a round-robfashion along multiple links within an IMA link group or groups. The FPrunning IMA in Passport B re-aggregates the cell stream at the receivingof the link group on a cell-by-cell basis, preserving the original cell order aformat.

Physical layer

ATM layer

ATM adaptation layer

Upper layers

ATM Layers IMA Sublayers

Interface specific part

IMA specific part

Physical mediumdependent sublayer

Transmission convergencesublayer



Figure 4An IMA link group between two eight-port DS1/E1 ATM FPs supporting IMA (Passport 7400)

o

o

o

o

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Eight-port DS1/E1 ATM FPs

FP onPassport A

FP onPassport B

o

o

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o

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ATM Interface(from/to ATM Layer)


Example -Cell transmit sequence:1, 2, 3, 4, 5, 6, 7, 8, 9, 10...

1, 6

2, 7

3, 8

4. 9

5, 10

Re-aggregated cellsequence at receive end:1, 2, 3, 4, 5, 6, 7, 8, 9, 10...

Cells on five individual DS1/E1 links forming a link group

241-5701-730 5.1S1


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Figure 5IMA link groups between two four-port DS3Ch ATM FPs supporting IMA (Passport 15000 or20000)

The figure “Detailed view of multiple IMA link groups between two eight-port DS1/E1 ATM FPs (Passport 7400)” (page 40) illustrates how the IMfeature distributes and combines an ATM layer cell sequence over multiIMA link groups. Each IMA link group is associated with an ATM interfaceThe stream of cell traffic is distributed in a round-robin fashion over eachphysical link in the IMA link group. For example, the cell stream for IMA linkgroup 0 is distributed over the three links in its group. IMA link group 2contains only one physical link; therefore, its cell sequence is unchangefrom the incoming transmit sequence.

Four-port DS3Ch ATM FPs

FP onPassport A

FP onPassport B



T3 lines oo

DS3 cells travel across the T3 lines



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Figure 6Detailed view of multiple IMA link groups between two eight-port DS1/E1 ATM FPs(Passport 7400)

The figure “Detailed view of multiple IMA link groups and independent linkforming in a four-port DS3Ch ATM FP (Passport 15000 or 20000)” (page 4illustrates how the IMA feature distributes and combines ATM layer cellsequences over multiple IMA link groups and independent links. Cell traffrom the ACM2 processor running IMA is multiplexed from DS1 to DS3format and is shunted out of the FP on the DS3 ports. The flow isbidirectional: in the opposite direction, cell traffic is demultiplexed from DSto DS1 format.

o

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Eight-portDS1/E1 ATM FPs

FP in Passport A

FP inPassport B

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Example -Cell transmit sequence:1, 2, 3, 4, 5, 6, 7, 8, 9, 10...

1, 4

2, 5

3, 6

1, 5

2, 6

DS1/E1 link

cells on individual links

Re-aggregated cellsequence at receive end:1, 2, 3, 4, 5, 6, 7, 8, 9, 10...

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IMA 1

IMA 2

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IMA 0

IMA 1

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3, 7

4, 8

1,2,3,4,5,6...

241-5701-730 5.1S1


Figure 7Detailed view of multiple IMA link groups and independent links forming in a four-port DS3ChATM FP (Passport 15000 or 20000)

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IMA framing and controlIMA control protocol (ICP) cells, one of two types of operations andmaintenance (OAM) cells used with IMA, control the distribution of ATMcells over an IMA link group.

ICP OAM cells perform two basic functions:

• maintain synchronization on a link and facilitate the determination odifferential delay between links

• convey IMA configuration and status information

ATM cells being transmitted over a link are apportioned into framescontaining 128 cells, permitting the insertion of one ICP cell within eachframe on a physical link. Each ICP cell appears in a different position witha frame on different links within the IMA link group, but in the same positiofrom frame-to-frame on any given link.

ICP cell distributionThe figure “Example of IMA framing and ICP cell distribution on a linkgroup” (page 43) shows an example of the distribution of ICP cells overdifferent physical links or logical links within an IMA link group. To simplifythe example, the transmission of cells is shown only from Passport B toPassport A. For example, on link 0 in the figure “Example of IMA framingand ICP cell distribution on a link group” (page 43), the ICP cell alwaysappears as the first cell in each frame; on link 1, the ICP cells always appas the fourth cell in each frame.

241-5701-730 5.1S1


Figure 8Example of IMA framing and ICP cell distribution on a link group

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FP running IMAin Passport A

IMA Frame 0 IMA Frame 1 IMA Frame 2

link 0

0

... ICICP ICP ...

FP running IMAin Passport B

0 1 2 3 127cell #

0 1 2 3 127 0 1 2 3 127

...

... ICPICP ICP ...0 1 2 3 127 0 1 2 3 127 0 1 2 3 127

...

... ICPICP ICP ...0 1 2 3 127 0 1 2 3 127 0 1 2 3 127

...

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ICP cell contentsICP cells contain information on the cell, the IMA frame, the physical linkthe IMA link group, and the individual links. Two ICP cell formats appear ithis section. Passport supports both the ATM Forum IMA and the proprietaIMA protocols for IMA services on the eight-port DS1/E1 ATM FPs. ForIMA services on the 32-port DS1/E1 Multiservice Access FPs and the foport DS3Ch ATM FP, Passport supports only the ATM Forum IMA protocoFor more information on IMA protocols supported on Passport, see “IMAprotocols” (page 30). Two ICP cell formats appear in this section:

• the figure “Contents of an ATM Forum IMA protocol ICP cell on allPassport 7400, 15000, 20000 FPs supporting IMA” (page 45) showscontents of an ATM Forum protocol ICP cell

• the figure “Contents of a proprietary IMA protocol ICP cell on the eighport DS1/E1 ATM FPs supporting IMA” (page 46) shows the contentsa proprietary protocol ICP cell

241-5701-730 5.1S1


Figure 9Contents of an ATM Forum IMA protocol ICP cell on all Passport 7400, 15000, 20000 FPssupporting IMA

0

OAM cell type

Cell type/link ID

ICP cell offset

Link stuff indication

IMA link group ID

CRC-10

Status change indication

IMA group status and control

Link 1 status

Link 2 status

Link 31 status

Unused

ATM cell header

Link 0 status

indicates IMA OAM cell type

indicates whether cell is ICP or filler cell; alsoindicates the logical link identifier

•••

provides the position of the ICP cell in the IMAframe

warns of an upcoming stuff cell

provides the sequence number of the framecontaining the cell

increments with every status change occurringwithin the link group

provides transmit and receive status of all linksas well as remote defect indicators; includesinformation on whether a link - is in/out of link group - is active/inactive - has any errors

IMA fields

IMA frame sequence number

provides status of IMA group and IMA framelength

Cyclical redundancy check, as defined forphysical layer OAM cells

Contains fixed VPI, VCI, PTI, and CLP values

link group identifier

Tx test Control

Tx test pattern

Rx test pattern

Transmit timing information

End-to-end channel

indicates the synchronization and timingreference link used by the transmit end

used to implement the test pattern procedure.See “Internal procedures for IMA linkconfiguration” (page 48)

Not used in Passport’s ATM Forum protocol



Figure 10Contents of a proprietary IMA protocol ICP cell on the eight-port DS1/E1 ATM FPs supportingIMA

0

OAM cell type

Cell type/link ID

ICP cell offset

Link stuff indication

IMA link group ID

CRC-10

Status change indication

IMA group status and control

Link 1 status

Link 2 status

Link 31 status

Unused

ATM cell header

Link 0 status

indicates IMA OAM cell type

indicates whether cell is ICP or filler cell; alsoindicates the logical link identifier

•••

provides the position of the ICP cell in the IMA

warns of an upcoming stuff cell

provides the sequence number of the framecontaining the cell

increments with every status change occurringwithin the link group

provides transmit and receive status of all linksas well as remote defect indicators; includesinformation on whether a link: - is in/out of link group - is active/inactive - has any errors

IMA fields

IMA frame sequence number

provides status of IMA group and IMA framelength

Cyclical redundancy check, as defined forphysical layer OAM cells

Contains fixed VPI, VCI, PTI, and CLP values

Unused

link group identifier

241-5701-730 5.1S1


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Cell rate decoupling using filler cellsCell rate decoupling guarantees that the physical links in an IMA link groucontinue to transmit cells when there are not enough user cells availablesaturate the links. The decoupling process injects an OAM type filler celsatisfy the cell rate requirement on each physical link. These filler cells arequired any time there is a cell transmit opportunity on a physical link, bno cells are available from the ATM interface.

Note:Filler cells are the IMA equivalent to physical layer idle cells.

The IMA cell machine generates filler cells at the transmit side of a link aremoves them on the receive side. Filler cells are actually blank ICP cells;cell type and link ID field indicates whether an ICP cell is a filler cell or n(See the figure “Contents of a proprietary IMA protocol ICP cell on the eigport DS1/E1 ATM FPs supporting IMA” (page 46).) If a cell is a filler cell,then the remaining ICP fields are empty.

Link capacity within an IMA link groupThe process of IMA framing and control slightly reduces the capacity ofindividual physical links in an IMA link group to transmit cells. Also, linkcapacity can differ between IMA link groups depending on the IMA protocused.

For more information on IMA link group capacity, contact your NortelNetworks account representative.

IMA link statesIMA groups on different nodes communicate link status information by usiICP cells to signal to the far-end IMA link group. Communication betweeIMA groups is established by a handshaking sequence that occurs betwboth ends of the link group. For details, see “Internal procedures for IMA linconfiguration” (page 48). The figures “Contents of an ATM Forum IMAprotocol ICP cell on all Passport 7400, 15000, 20000 FPs supporting IM(page 45) and “Contents of a proprietary IMA protocol ICP cell on the eigport DS1/E1 ATM FPs supporting IMA” (page 46) show the link status fieldin an ICP cell.



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Internal procedures for IMA link configurationThis section summarizes the link configuration procedures that are defininternally to the IMA process, based on how IMA is configured at both enof a link group. They are executed transparently to users after configurinIMA on Passport FPs at the near and far end of the IMA link group:

• IMA link group startup - a handshaking sequence occurring betweentwo ends of a link group; permits each end of the link to resolve theirespective link identifiers (LIDs) and verify connectivity

• link addition (to an IMA link group) - as a result of provisioning at bothends of a link group

• link deletion (from an IMA link group) - as a result of provisioning ateither end of a link group

• link deactivation (from an IMA link group) - due to a fault on a link or aviolation of the IMA protocol

For example, the differential delay of one link relative to its peers in IMA link group may increase such that the link must be removed frothe link group (See “Compensating for differential delay” (page 56).)

• link reactivation (as part an IMA link group) - due to the recovery of link from a fault on the link or from a violation of the IMA protocol

For example, the differential delay of one link relative to its peers in link group may decrease such that the link can be re-admitted to the lgroup.

Only the ATM Forum IMA protocol uses the test pattern procedure asspecified inInverse Multiplexing for ATM (IMA) Specification. Thisprocedure is used during link group startup, link addition and link reactivatito determine if there are any links in the IMA link group that aremisconnected. If a link is determined to be misconnected, it is not activain the IMA link group.

Adding inactive links to an IMA link groupThe IMA application incorporates a process to determine how often it wiattempt to admit inactive links to an IMA link group. A user can control thamount of time that the IMA application waits between attempts to add

241-5701-730 5.1S1


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inactive links to a link group by setting thelinkRetryTimeout attribute. Thisattribute can be assigned a value anywhere between 0 and 1000 secondsthe default value of 10 seconds. The process of attempting to add inactilinks itself takes a few seconds because of the protocol involved

Note:ThelinkRetryTimeoutattribute is not a configurable attribute whenusing the 32-port DS1/E1 Multiservice Access function processor. Italways set to the default value, 1 second.

The different conditions specified in the following list determine the responof the IMA application when there are inactive links in an IMA link group

• after the startup procedure

• when the IMA link group is functioning

• after the link addition and reactivation procedure

After the startup procedureIf the Startup procedure is successful but not all links in an IMA link grouare active, the IMA application waits the amount of time specified by thelinkRetryTimeoutattribute before invoking the link addition and reactivationprocedure for all inactive links in the link group.

When the IMA link group is functioningIf an IMA link group is functioning with all configured links active, the IMAapplication will initiate the link addition and reactivation procedure when

• a link fails; this may occur due to the physical link going down, a lossIMA frame (LIF) failure, or a remote link failure.

• a loss of delay synchronization (LODS) failure occurs in an IMA linkgroup (for details, see “Ongoing monitoring of differential delay”(page 57))

• the remote end of the IMA link indicates that it is executing a linkaddition and reactivation procedure (proprietary protocol only)

• a configuration change is made that either

— adds or deletes links, or

— modifies the provisionable attributesmaxDiffDelay orlinkSelectionCriterion



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For details on these attributes, see 241-5701-060Passport 7400, 15000,20000 Components. For a discussion of differential delay, see “Compensatinfor differential delay” (page 56).

After the link addition and reactivation procedureIf not all links in the IMA link group are active upon the completion of thelink addition and reactivation procedure (whether a link has been addednot), the IMA application waits the amount of time specified by thelinkRetryTimeoutattribute before invoking the link addition and reactivationprocedure for all inactive links in the link group.

Compensating for asynchronous physical linksCell stuffing is a technique used to maintain IMA synchronization in linkgroups containing asynchronous physical links. Line clock rates overdifferent links that derive their clock from different sources can vary up to 1ppm due to the frequency tolerance of clock generators permitted in the DE1physical layer standards.

Note 1: This is not the same issue as differential delay discussed in“Compensating for differential delay” (page 56).

Note 2: Cell stuffing to compensate for asynchronous physical links used by IMA link groups in independent transmit clock (ITC) mode onlFor details on clock mode and IMA link groups, see “Transmit clockmode” (page 52).

To prevent the physical link from being starved of ATM cells, stuff cells ainserted on physical links in an IMA link group that are operating at a fastclock rate than the slowest link. Stuff cells are added by the IMA cell machion an FP running IMA after round-robin cell distribution has occurred at thtransmit side of a link group. A stuff cell is merely a copy of an ICP cell analways follows immediately after an ICP cell in an IMA frame. The “link stufindication” field of an ICP cell indicates to the remote end the location of tstuff cell (see the figure “Contents of an ATM Forum IMA protocol ICP ceon all Passport 7400, 15000, 20000 FPs supporting IMA” (page 45)).

Cell stuffing prevents the physical layer interface from inserting idle cellscompensate for differences in clock synchronization, which would disruptIMA process.

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For example, in the figure “Example of cell stuffing to preserve the ordercells over links running at different speeds” (page 51), physical links 0 anare part of the same IMA link group. It is evident by IMA frame 17 that link0 is running slightly faster than link 1. By frame 35, a stuff cell is added tosynchronize the cells on the two links. Cell stuffing occurs as required to althe cells on different links in a link group.

Figure 11Example of cell stuffing to preserve the order of cells over links running at different speeds



o o

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IMA frame 0 IMA frame 17 IMA frame 35

link 0

... ICPICP ICP ...0 1 2 3 127

cell #0 1 2 3 127 0 1 2 3 127

...

... ICPICP ICP ...0 1 2 3 127 0 1 2 3 127 0 1 2 3 127

...

link 1

...


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Transmit clock modeThere are two modes of transmit clocking on IMA link groups, as specifiedInverse Multiplexing for ATM (IMA) Specification:

• Common transmit clock (CTC) mode

• Independent transmit clock (ITC) mode

In CTC mode, the same transmit clock reference is used for all physical linin the IMA link group. In ITC mode, the transmit clock may be derived fromdifferent references on one or more physical links in the IMA link group. Thfollowing table “Transmit clock mode supported by the different IMAprotocols on Passport” (page 52) indicates the transmit clock modessupported by the ATM Forum protocol and the proprietary protocol.

Table 5Transmit clock mode supported by the different IMA protocols onPassport

Transmit clock modesupported by:

Function processor ProductATM ForumIMA protocol

ProprietaryIMA protocol

eight-port DS1 ATMFP

Passport 7400 • CTC mode

• ITC mode

• ITC mode

eight-port E1 ATM FP Passport 7400 • CTC mode

• ITC mode

• ITC mode

Note 1: IMA services provided by the 32-port DS1/E1 Multiservice AccessFPs and the four-port DS3Ch ATM FP do not support the proprietary IMAprotocol.

Note 2: The Passport implementation of ITC mode using the ATM Forumprotocol differs from that specified in Inverse Multiplexing for ATM (IMA)Specification. For details, see “The Passport implementation of ITC mode”(page 55).

(Sheet 1 of 2)

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The technique of cell stuffing to compensate for asynchronous physical liis used only by IMA link groups in independent transmit clock (ITC) modeWhen common transmit clock (CTC) mode is used, there are no differenin the clock rate used by different physical links. Therefore, no cell stuffingrequired to maintain clock synchronization. However, to comply with theInverse Multiplexing for ATM (IMA) Specification, cell stuffing occurs inCTC mode every 2 048 cells transmitted on each link in the IMA link grou

Common transmit clock (CTC) modeCTC mode is supported on the ATM Forum IMA protocol for IMA serviceprovided through the eight-port DS1/E1 and the 32-port DS1/E1 MultiservAccess FPs (see the table “Transmit clock mode supported by the differ

32-port DS1Multiservice AccessFP


• ITC mode

See Note 1

32-port E1Multiservice AccessFP


• ITC mode

See Note 1

four-port DS3Ch ATMFP

Passport 15000and 20000

• CTC mode

• ITC mode

See Note 1

Table 5 (continued)Transmit clock mode supported by the different IMA protocols onPassport

Transmit clock modesupported by:

Function processor ProductATM ForumIMA protocol

ProprietaryIMA protocol

Note 1: IMA services provided by the 32-port DS1/E1 Multiservice AccessFPs and the four-port DS3Ch ATM FP do not support the proprietary IMAprotocol.

Note 2: The Passport implementation of ITC mode using the ATM Forumprotocol differs from that specified in Inverse Multiplexing for ATM (IMA)Specification. For details, see “The Passport implementation of ITC mode”(page 55).

(Sheet 2 of 2)



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IMA protocols on Passport” (page 52)). When using this mode, the operamust ensure that all links in the IMA link group use the same transmit clocFor example, all physical links could use a clocking source of

• module

• line (if the transmit clocks at the far end are all derived from the samsource)

If you are using CTC mode, and not all links in an IMA link group use thsame transmit clock reference, corruption or loss of data may occur. If youthe module clocking source, clocking will be synchronous across all por

Passport inserts a stuff event after every 2 048 cells transmitted on eachin an IMA link group using CTC mode, as described in ATM ForumInverseMultiplexing for ATM (IMA) Specification. Cell stuffing to compensate fortiming differences between links is suppressed in CTC mode.

Note:For information on network clock synchronization on Passport, s241-5701-600Passport 7400, 15000, 20000 Configuration Guide.

Independent transmit clock (ITC) modeIMA services on any of the Passport function processors providing IMAcapability, support the ITC mode on the ATM Forum IMA protocol. Passpoalso supports the ITC mode on the proprietary IMA protocol for IMA serviceon the eight-port DS1/E1 ATM FPs. See the table “Transmit clock modesupported by the different IMA protocols on Passport” (page 52)).

If ITC mode is used, links in the IMA link group may use the same ordifferent transmit clock references, provided the clock tolerance on each lis within 50 ppm (the maximum specified by the DS1). IMA link groupsconfigured to operate in ITC mode use cell stuffing as a technique formaintaining IMA synchronization. For a description of cell stuffing, see“Compensating for asynchronous physical links” (page 50)

In a typical ITC mode configuration, all physical links use a clocking sourof line and the clocks on the incoming links are derived from differentreferences.

241-5701-730 5.1S1


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Note:For information on network clock synchronization on Passport, s241-5701-600Passport 7400, 15000, 20000 Configuration Guide.

The Passport implementation of ITC modeThe Passport implementation of ITC mode is different from what is specifiin the ATM ForumInverse Multiplexing for ATM (IMA) Specification. Thespecification states that a stuff event is to be inserted on the transmit referelink after every 2 048 cells transmitted on the link. Stuff events are inseron the other links in an IMA link group, as required, to keep themsynchronized with the transmit reference link.

In ITC mode, Passport does not insert stuff events on the transmit referelink after every 2 048 cells. Instead, it synchronizes all links in the IMA lingroup to the slowest link in the link group (see “Compensating forasynchronous physical links” (page 50)). Since the slowest link is used asreference, no stuffing is required on that link. Stuff events are inserted onother links as required to keep them synchronized with the slowest link. signalling purposes, Passport selects one of the active links as the transreference link.

Interoperability considerations using ITC modeWhile Passport-to-Passport interoperability is guaranteed in ITC mode, thmay be some issues for interoperability with non-Passport equipment inmode. Interoperability may not be possible if the receive IMA on the nonPassport equipment requires stuff events on the transmit reference link every 2 048 cells for proper operation.

The Passport IMA receiver is capable of operation with an IMA transmittthat uses either the Passport ITC implementation or an ITC modeimplementation compliant with the ATM Forum specification.

Guidelines for transmit clock modeThe following guidelines apply to the transmit clock mode used on Passp

• If all links in the IMA link group use the same transmit clock, use CTmode. This guarantees interoperability with equipment compliant to tATM Forum Inverse Multiplexing for ATM (IMA) Specification.



ust

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• If links in the IMA link group use different transmit clocks, then youmust use ITC mode. Interoperability with non-Passport equipment mbe determined on a case-by-case basis.

• The transmit clock mode does not need to be the same at each end olink.

Compensating for differential delayPhysical links within an IMA link group may encounter different cell transfedelays that can also vary over time on each individual link. Cells transmittover different links in a given order may not be received in the same ordethe far end due to differential delay. In fact, a cell transmitted before othecells in the original stream may arrive at the receiving end after those cellhad originally preceeded.

Note:This is not the same issue as variations in transmit clock tolerandiscussed in “Compensating for asynchronous physical links” (page 5

Differential delay is a factor of the length of time that cells may spend ondifferent links due to the length of the transmission path, the use oftransmission media (such as satellite technology) or delays introduced bintermediate equipment. “Lagging” physical links (ones with a longer celtransit time) store more cells on a link than the “leading” links (those with thshortest cell transit time).

Using cell buffers to maintain link delay synchronizationThe IMA cell machine in the FP at the receiving end of an IMA link groupmust be able to re-establish the cell order of the original stream. To do so,device

1 measures differential delay over the various links

2 buffers cells received on each link based on the measured differentidelay, thereby equalizing the differential delay before recombining thcells into the original stream

Buffers impose an equal transit time on all links. The “leading” link in a lingroup (the link with the shortest delay) has the longest cell buffer, and thmost “lagging” link (the one with the longest delay) has the shortest buff

241-5701-730 5.1S1


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When the receiving end of an IMA link group has measured and compensafor the differential delay over a physical link, then the link is considered toin link delay synchronization (LDS).

Measuring differential delay during IMA link group startupIn the process of establishing communication with the FP at the far end link during IMA link group startup or link addition and reactivation (see“Internal procedures for IMA link configuration” (page 48)), the IMA featuremeasures the differential delay over each physical link at the receive enThere can be one of two results:

• If the delay over a link relative to other links iswithin a specifiedmaximum value, then the link is considered to be in LDS and can beincluded as an active member of the IMA link group.

• If the delay over a link relative to other linksexceedsthe maximum value,then the link is not in LDS and is rejected as an active member of the IMlink group.

When both ends of an IMA link group agree on which links are within LDSthey can start exchanging user cells.

Ongoing monitoring of differential delayThe IMA feature continually monitors and compensates for the differentidelay of links within a link group. If the delay on a link changes such thaexceeds the specified maximum differential delay plus one millisecond, link is considered to have lost its delay synchronization; that is, the link hexperienced a loss of delay synchronization (LODS), and is deactivated frthe IMA link group. A link is removed from an IMA link group immediatelywhen a LODS state is detected.

For example, in the figure “Measuring differential delay over links in an IMlink group” (page 58), cell 4 is experiencing a delay of 200 milliseconds ovlink 3. If the differential delay is set to 100 milliseconds (the maximum), thelinks 0, 1, 2 and 4 can remain in the link group, while link 3 must be remove

Note:The ATM hardware is designed to tolerate a differential delay o1 millisecond greater than the maximum provisioned for the attributemaxDiffDelay. For example, you may see a delay of 26 millisecondswhen the provisioned maximum is 25 milliseconds.



g

Figure 12Measuring differential delay over links in an IMA link group

Link selection criteriaWhen not all of the links in an IMA link group conform to the maximumdifferential delay, you can choose one of the following criteria for selectinwhich links should be deactivated and which ones should remain active:

• maximum bandwidth

• minimum delay

PPT 3141 001 AA

ATM layercell transmitsequence:1, 2, 3, 4, 5...



link 0

link 1

link 2

link 3

link 4

cell 1

cell 2

cell 3

cell 4

cell 5

50 milliseconds

25 milliseconds

80 milliseconds

200 milliseconds

60 milliseconds

Total time to different cells on each physical link

Direction of cell flow

Examples of delay:

241-5701-730 5.1S1


kn

m

Note: The 32-port DS1/E1 Multiservice Access FP only supports linselection based on minimum delay. For this FP only, the link selectiocriterion minimum delay is the value of theIma attributelinkSelectionDelay leastDelay.

The default is maximum bandwidth. The figure “Example of an IMA linkgroup illustrating different link selection criteria” (page 60) provides anexample illustrating the two selection criteria. If you configure a maximudifferential delay of 20 milliseconds for the IMA link group, then twodifferent sets of links would be activated depending on the link selectioncriteria:

• If you have chosen to minimize delay, then links 1 and 3 would beselected.

• If you have chosen to maximize bandwidth links 0, 1 and 2 would beselected.



s

Figure 13Example of an IMA link group illustrating different link selection criteria

ATM IMA service reliability on Passport 15000 forSuccession Networks

Note:This feature is not generally available. Contact Nortel Networkfor more information on this feature.

PPT 3141 002 AA



link 0

link 1

link 2

link 3

cell 1

cell 2

cell 3

cell 4

50 milliseconds

40 milliseconds

60 milliseconds

20 milliseconds

Direction of cell flow

Link delay (milliseconds)

Link 3 Link 1 Link 0 Link 2

Examples of delayover each link

0 10 20 30 40 50 60 70

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On Passport 15000 for Succession Networks, the IMA ATM feature(imaAtmForumHot) offers hitless equipment protection and softwaremigration for ATM services running over IMA in one-for-one equipmentprotected scenarios on the 4-port DS3 Ch Atm FP.

The following ATM services offer a hitless service:

• PVCs (VCCs and VPCs)

• point-to-point SVCs

• source and destination SPVCs

• point-to-point SVPs

• source and destination SPVPs

• nailed-up relay points

• switched relay points

The ATM hitless services can be offered on up to:

• 56 ATM interfaces per FP (UNI and PNNI) in non-associated signallinconfigurations

• 5500 ATM connections per FP

— 2600 SVCs for voice calls

— 2600 PVCs/SPVCs/SVCs for DSL or voice calls

— 300 PVCs/SPVCs/SVCs for internal control purposes

• 28 DS1s per IMA group

• 56 IMA groups per FP

Hot standby applications and features can run uninterrupted, even whenhardware providing that service changes. This means they can offer hitlservices during equipment protection switchover and hitless softwaremigration. This is done by operating with a standby instance of the softwthat is fully synchronized with the active instance of the software. Hotstandby applications and features use equipment sparing of FPs to incu



ree

02tals

ct

belsed,

minimal interruption of cell forwarding and maintain any connections that aestablished. This ability reduces service down time and increases servicreliability.

The IMA ATM feature (imaAtmForumHot) provides hot standbyfunctionality only when it is provisioned on a one-for-one (1:1) spared4pDS3ChAtm LP and using a 1:1 sparing panel.

For information on:

• hitless ATM services on Passport 15000 and 20000, see 241-5701-7Passport 7400, 15000, 20000 ATM Routing and Signaling Fundamen

• hitless software migration on Passport 15000 and 20000, see241-5701-272Passport 7400, 15000, 20000 Software Upgrade

• hitless services and hot, warm, and cold standby applications andfeatures, see 241-5701-600Passport 7400, 15000, 20000 ConfigurationGuide.

Note:Succession Networks customers must use the templates in241-6001-011Preside MDM Fault Management User Guide toconfigure IMA.

ATM control channel failure on IMAATM control channels, which include signaling, ILMI, and RCC are subjeto the CBC algorithm on IMA links. If a link in the IMA group fails, abandwidth reduction occurs and one or more of the control channels maytorn down if there is insufficient bandwidth available. The control channewill not reestablish until the link recovers or other connections are releasfreeing bandwidth and allowing the control channels to be admitted.

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63

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intion

:

Chapter 3Configuring IMA

This section describes the components and attributes associated with thinverse multiplexing over ATM (IMA) feature and shows how to configureIMA on Passport 7400, 8700, 15000. The configuring procedures shownthis section is intended to be used with Passport’s component administrasystem (CAS) and may be performed using a local VT100 terminal or aremote connection (such as telnet).

Note:Succession Networks customers must use the templates in241-6001-011Preside MDM Fault Management User Guide toconfigure IMA.

This section provides details on the following aspects of IMA configuring

• “Prerequisites to configuring IMA” (page 64)

• “IMA and the ATM interface” (page 65)

• “IMA and the ATM interface” (page 65)

• “IMA components and configurable attributes” (page 66)

• “IMA configuring links” (page 68)

• “Notes about configuring IMA” (page 71)

• “Mixed configurations” (page 72)

• “Configuring IMA link groups and independent links” (page 77)

• “Migrating software releases” (page 86)

• “Upgrading IMA groups to the ATM Forum IMA protocol” (page 87)


64 Chapter 3 Configuring IMA

A

e

tall

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r

e

e

Prerequisites to configuring IMASeveral prerequisites must be fulfilled before you can begin configuring IMon a Passport node.

• For IMA services on a Passport 7400 node, you must have one of thPassport FPs supporting IMA installed on your Passport node:

— eight-port DS1 ATM FP

— eight-port E1 ATM FP

— 32-port DS1 Multiservice Access FP

— 32-port E1 Multiservice Access FP

• For IMA services on a Passport 15000 or 20000 node, you must insthe four-port DS3Ch ATM FP installed on your Passport node:

• You can configure the ports with independent ATM links or as a mixeconfiguration containing both independent links and IMA links. Formore information about configuring the port components forindependent links, see 241-5701-710Passport 7400, 15000, 20000 ATMConfiguration Guide. Also, see “Mixed configurations” (page 72).

• The customer equipment cables consisting of the actual physicalconnections between Passport nodes must be in place and properlyconnected to the termination panel, which is in turn connected to thephysical connector ports on the FP. See the following documents fodetails on the cabling connections for the FPs that run IMA:

— 241-7401-200Passport 7400 Hardware Description

— 241-1501-200Passport 15000, 20000 Hardware Description

— 241-7401-240Passport 7400 Hardware Installation, Maintenanceand Upgrade

— 241-1501-210Passport 15000, 20000 Hardware Installation Guid

— 241-1501-215Passport 15000, 20000 Hardware MaintenanceGuide

• You should have access to all necessary configuring information. Se241-5701-060Passport 7400, 15000, 20000 Components forinformation on the configurable attributes for IMA.

241-5701-730 5.1S1

Chapter 3 Configuring IMA 65

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onures

• Be aware of the configuration options for ports on the FPs supportinIMA. See 241-5701-615Passport 7400, 15000, 20000 FP ConfigurationReference for details.

• For information on configuring trunks for IMA, see 241-5701-420Passport 7400, 15000, 20000 Trunking Guide.

• Use the procedures in 241-5701-270Passport 7400, 15000, 20000Software Installation Guideto install the base Passport software, beforconfiguring IMA.

Note: See “IMA protocols” (page 30) for information regardingPassport releases supporting the IMA feature.

• The procedures provided in this section assume that you are configuin edit mode. For introductory discussions on configuring andconfiguration views, see 241-5701-045Passport 7400, 15000, 20000Management System User Interface Guide.

MSA32 configuration pre-requisitesMSA32 has special considerations when deploying IMA. See “Provisioniconfigurations for the 32-port DS1/E1 Multiservice Access functionprocessors” (page 28).

IMA and the ATM interfaceTo transmit user cells, the Passport node must have access to an ATMinterface to link to an IMA link group. The table “Where to find informationon ATM connection types that can be transported over an IMA link groupPassport 7400, Passport 15000 and 20000” (page 66) lists the ATM featand services and shows where you can find information in the Passportdocumentation suite.



lso

s

IMA components and configurable attributesThis section summarizes the components and configurable attributesreflecting IMA on Passport’s component administration system (CAS). It aincludes a description of the configuring links required for IMA.

The IMA component tree is shown in the figure “IMA feature componentand configurable attributes” (page 67). TheIma subcomponents of theLpcomponent and theLp DS3subcomponent allow configuring access to anIMA link group. Link andTestare sub-components of theLp ImaandLp DS3Imasubcomponents.

Table 6Where to find information on ATM connection types that can betransported over an IMA link group on Passport 7400, Passport 15000and 20000

Feature/service Document

ATM bearer service 241-5701-700 Passport 7400, 15000,20000 ATM Overview

ATM direct and logical trunks(AAL5)

241-5701-420 Passport 7400, 15000,20000 Trunking Guide

Circuit Emulation (AAL1) 241-5701-720 Passport 7400, 15000,20000 AAL1 Circuit Emulation Guide

ATM multiprotocolencapsulation (MPE)

241-5701-805 Passport 7400, 15000,20000 Understanding IP

Frame relay over ATM 241-5701-920 Passport 7400, 15000,20000 Frame Relay to ATM InterworkingGuide

241-5701-730 5.1S1


Figure 14IMA feature components and configurable attributes

InverseMultiplexerAtm (Ima)

Link (Lk)

DS1

DS3

LogicalProcessor (Lp)

EM


Test (Test)

Componentattribute

protocol (prot)transmitClockMode (clock)linkRetryTimeout (retry)maxDiffDelay (delay)linkSelectionCriterion (select)

interfaceName

Link (Lk)

Test (Test)

See attributes listing under Lp Ima

See attributes listing under Lp Ima Lk

DS1Channel (Chan)

Channel (Chan)

E1Channel (Chan)



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rtantion

P. are

0)

A background description of the role of several key configurable attributeunder theIma component is available in the following sections:

• maxDiffDelay: “Compensating for differential delay” (page 56)

• linkSelectionCriterion: “Link selection criteria” (page 58)

• linkRetryTimeout: “Adding inactive links to an IMA link group”(page 48)

• transmitClockMode: “Transmit clock mode” (page 52)

• protocol: “IMA protocols” (page 30)

A complete description of the IMA components and attributes is provided241-5701-060Passport 7400, 15000, 20000 Components.

IMA configuring linksThere are three groups of components (or subcomponents) that are impoto the IMA configuring process for Passport nodes using any of the functprocessors supporting the IMA application:

• IMA

• ATM port management

• ATM interface

The ATM port management and IMA subcomponents both exist under theLpcomponent. The logical processor used for IMA is linked to theCardsubcomponent under theShelf component; this specifies the location on thePassport shelf where the function processor running IMA resides.

Through configuration, associate each IMALink subcomponent with theChannel subcomponent of a unique instance of a E1 or DS1 link on the FChannel 0 (the default value) is recommended even though other valuesallowed. Configure all timeslots for this channel.

The figure “Component hierarchy showing examples of configuring linksrequired for IMA using the eight-port E1 ATM FP (Passport 7400)” (page 7shows the component hierarchy for theIma feature on the eight-port E1 ATMFP, including the required configuring links.

241-5701-730 5.1S1


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Passport can support a total of

• eight physical links in one link group on the eight-port DS1/E1 ATM FP

• eight physical links in one link group on the 32-port DS1/E1Multiservice Access FPs

• 28 logical links in one link group on the four-port DS3Ch ATM FPs

These links can have instance numbers within the range of 0 to 31. Forexample, an eight-port DS1/E1ATM FP with a full complement of eight linkforming a link group may include links with any combination of identifierssuch as:

• links 0, 1, 2, 3, 4, 5, 6, 7 or

• links 0, 5, 14, 23, 24, 25, 27, 31

With the 32-port DS1/E1 ATM FPs, you can configure a maximum of eigphysical links in an IMA link group, with the links having instance numberbetween 0 and 15 inclusive. IMA link groups on the 32-port DS1/E1 ATMFPs must contain physical links associated with ports in the range 0 to 1inclusive, or in the range 16 to 31 inclusive: all ports in an IMA link groupmust fall in one of these ranges.

If you want to transmit user cells over an IMA link, the IMA link group(represented by theIma/1subcomponent in the figure “Component hierarchshowing examples of configuring links required for IMA using the eight-poE1 ATM FP (Passport 7400)” (page 70)) must be linked to an ATM interfa(represented by theAtmIf). All connections associated with the ATMinterface are transmitted over the IMA link group. Link instance numbersmust be unique within one IMA link group, but do not have to be uniqueamong different IMA groups.



Figure 15Component hierarchy showing examples of configuring links required for IMA using theeight-port E1 ATM FP (Passport 7400)

Shelf

Root

E1/0

AtmCell

Chan/0

E1/1

AtmCell

Chan/0

Arc Aru

Card/1

Lp/1

IMA subcomponent

ATM port mgt. subcomponent

E1/2

AtmCell

Chan/0

AtmIf/10

Ca

Vcc/7.84

Vcd

Root

other component

dynamic subcomponent

ATM interface component

configured link

AtmIf/11

Ca

Vcc/4.32

Vcd

Ima/1

Link/2Link/1 Test

Test Test Test

241-5701-730 5.1S1


Notes about configuring IMAFor information on how to configure features on a Passport node, see241-5701-270Passport 7400, 15000, 20000 Software Installation Guide:

For information on operator and configuration commands, see241-5701-050Passport 7400, 15000, 20000 Commands.

Before you begin configuring theIma feature, note the following

• TheImafeatures may be used on an LP only if the associatedcardTypeis

— 8pDS1Atm (for Passport 7400)

— 8pE1Atm (for Passport 7400)

— 32pDS1Msa (for Passport 7400)

— 32pE1Msa (for Passport 7400)

— 4pDS3ChAtm (for Passport 15000 and 20000)

• An Ima component can be added only to an LP with a feature setcontaining

— ima or ImaAtmForum (for the eight-port DS1/E1 ATM FPs)

— ImaAtmForum (for the 32-port Ds1/E1 Multiservice Access FPs,and the four-port DS3Ch ATM FP)

• An Ima component must have at least oneLink subcomponent.

• An Imacomponent must be bound to anAtmIfcomponent or not boundto anything at all.

• All Link subcomponents of anIma component must be bound toChancomponents residing on the same LP as theIma component.

• For the four-port DS3Ch ATM FP, allDS1 components must have thesameclockingSource attribute value as their parentDS3 component.With a value ofsameAsDs3, theDS1 component will automatically usetheclockingSourcevalue specified by the parentDS3. The attribute valueis set by default tosameAsDs3 and is the only value permitted.

• For the four-port DS3Ch ATM FP, if theNetworkSynchronizationcomponent is present, both values of theclockingSource attributes forDS3 andDS1 components must be module.



beficndP

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• The eight-port DS1/E1 ATM FPs allow the traffic shaping feature to enabled or disabled. The ATM cell queue manager provides the trafshaping ability for the four-port DS3Ch ATM FP on Passport 15000 a20000. Similarly, traffic shaping on the 32-port Multiservice Access Fis provided automatically by the ATM cell queue manager.

• For the eight-port DS1/E1 ATM FPs, compatibility with earlier Passpoimplementations is only possible if you use the proprietary IMAprotocol. This is due to the incompatibility of the ATM Forum IMAprotocol with the proprietary IMA protocol. Note that Passport 15000and 20000 support only the ATM Forum IMA protocol. For moreinformation see “IMA protocols” (page 30).

Note: It is not a prerequisite to link the IMA application to an ATMinterface before configuring IMA. You can configure IMA and test theIMA application before configuring a link to an ATM interface (see thprocedure “Configuring the Passport FP supporting the IMA feature(page 77)). The section “Maintenance tests” (page 95) provides detaon manually testing the IMA application.

Mixed configurationsThe Passport FPs that provide IMA services, support a mixed configuraof independent ATM links and IMA link groups on the same FP. Thefollowing rules apply to configuring a mixed configuration:

• The instance number of IMA groups and independent links must beunique. For example anIma/0 and aDS1/0 independent link cannot co-exist on the same FP.

From a configuring perspective, an independent link is a DS1 or E1 lithat is bound by itsChannelsubcomponent to anAtmIfcomponent. Theinstance number of an independent link is the same as its DS1 or Ecomponent. For information about configuring DS1 or E1 or DS3 pocomponents, see 241-5701-600Passport 7400, 15000, 20000Configuration Guide. For information about configuring an ATMinterface, see 241-5701-710Passport 7400, 15000, 20000 ATMConfiguration Guide.

241-5701-730 5.1S1


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• For the Passport 7400 node using the eight-port DS1/E1 ATM FP, iftraffic shaping and per-Vc queuing are disabled on the LP, then theinstances of IMA groups and independent links can have values fromto 7. If either traffic shaping or per-Vc queuing is enabled onPassport 7400 node using the eight-port DS1/E1 ATM FP, then theinstances of IMA groups and independent links can have values fromto 3.

For the Passport 7400 node using the eight-port DS1/E1 ATM FP, iftraffic shaping and per-Vc queuing are disabled when there is noArcsubcomponent on the LP, or when theArc subcomponent is present andits perVcQueueInterfaces attribute is set to zero. If theperVcQueueInterfaces attribute is set a non-zero value, then per-Vcqueuing and traffic shaping are enabled.

The value of theArc component’sperVcQueueInterfaces attribute alsoindicates which IMA groups or independent links can have per-Vcqueuing and traffic shaping enabled:

— If the perVcQueueInterfaces is set to one, then only instance zero(that isIMA/0 or DS1/0) can have per-VC queuing and trafficshaping enabled.

— If the perVcQueueInterfaces attribute is set to two, then instanceszero and one can have per-Vc queuing and traffic shaping enab

— If the perVcQueueInterfaces attribute is set to four, then instanceszero to three can have per-Vc queuing and traffic shaping enabl

• The ATM cell queue manager automatically provides traffic shaping the 32-port Multiservice Access FP.

For more information about configuring traffic shaping on Passport, see following documents:






therts;

A

ctes

le.

Example of a mixed configuration without traffic shapingThe following figure “Example of a mixed configuration without trafficshaping on the eight-port E1 ATM FP (Passport 7400)” (page 74) showsrelationship between the FP’s physical ports and ATM ports. The ATM poare part of the FP’s cell queue controller (CQC), the ATM cell processorthese are the ports used by the ATM software.

This figure shows four independent links and two IMA link groups. The IMgroups (Ima/1andIma/5) each combine two physical ports into IMA virtualports.

Figure 16Example of a mixed configuration without traffic shaping on the eight-port E1 ATM FP (Passport 7400)

The example in the figure “Example of a mixed configuration without traffishaping on the eight-port E1 ATM FP (Passport 7400)” (page 74) illustrathe following configuring concepts:

• When traffic shaping is not being used, all eight ATM ports are availab

PPT 2103 001 AA

Physical ports

Ima/1

Ima/5

E1/0 –

E1/1 –

E1/2 –

E1/3 –

E1/4 –

E1/5 –

E1/6 –

E1/7 –

ATM ports on CQC

– 0

– 1

– 2

– 3

– 4

– 5

– 6

– 7

241-5701-730 5.1S1


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• The instance numbers for each independent link match the ATM pornumber. Note that each physical port used as an independent link infigure “Example of a mixed configuration without traffic shaping on theight-port E1 ATM FP (Passport 7400)” (page 74) matches the sameATM port number:

— E1/0

— E1/3

— E1/4

— E1/7

• Independent links and IMA groups cannot share the same instancenumbers. Note the instance numbers shown in the figure “Example mixed configuration without traffic shaping on the eight-port E1 ATM F(Passport 7400)” (page 74):

— E1/0

— Ima/1 (composed of physical links E1/1 and E1/2)

— E1/3

— E1/4

— Ima/5(composed of physical links E1/5 and E1/6)

— E1/7

• The configuration of IMA groups incorporate a high degree of flexibilitySpecifically, the IMA groups can use, without restriction, any physicalinks that are not being used as independent links. For example, in tfigure “Example of a mixed configuration without traffic shaping on theight-port E1 ATM FP (Passport 7400)” (page 74) the link groups Imaand Ima/5 could use any combination of physical links available.

Example of a mixed configuration with traffic shapingThe following figure shows a mixed configuration of three independent linand one IMA link group with traffic shaping enabled on the eight-port E1ATM FP. In this example, theperVcQueueInterfaces attribute is set to two,making traffic shaping available on ATM ports 0 and 1. Also, the IMA linkgroup Ima/1 combines five physical ports into one virtual port.



6)

rts

the

n

”ink

Figure 17Example of a mixed configuration with traffic shaping enabled on theeight-port E1 ATM FP (Passport 7400)

The example in the figure “Example of a mixed configuration with trafficshaping enabled on the eight-port E1 ATM FP (Passport 7400)” (page 7illustrates the following configuration concepts for Passport 7400:

• When traffic shaping is enabled, only four ATM ports are available (po0 to 3).

• Because theperVcQueueInterfacesattribute is set to two, two of the fourATM ports (instances 0 and 1) can use the traffic shaping feature. Inexample in the figure “Example of a mixed configuration with trafficshaping enabled on the eight-port E1 ATM FP (Passport 7400)”(page 76), the independent link E1/0 and the IMA link group Ima/1 catake advantage of the traffic shaping feature.

• As in the example in the figure “Example of a mixed configurationwithout traffic shaping on the eight-port E1 ATM FP (Passport 7400)(page 74), the instance numbers for each independent link and IMA lgroup matches the ATM port number.

PPT 2104 001 AA

Physical ports

TS - denotes that traffic shaping is available on a port

Ima/1

Ima/1

E1/0 –

E1/1 –

E1/2 –

E1/3 –

E1/4 –

E1/5 –

E1/6 –

E1/7 –

ATM ports on CQC

– 0 TS

– 1 TS

– 2

– 3

– 4

– 5

– 6

– 7

241-5701-730 5.1S1


an

• Independent links and IMA groups have distinct instance numbers.

Configuring IMA link groups and independent linksThis section provides the procedures to fully configure IMA link groups onfunction processor running theIma feature on a Passport switch. This sectioincludes the following procedures:

• “Configuring the Passport FP supporting the IMA feature” (page 77)

• “Configuring the ports, IMA link groups, and independent links”(page 79)

• “Configuring the ATM interface and linking it to an IMA link group oran independent link” (page 84)

Configuring the Passport FP supporting the IMA featureUnless otherwise specified in the following steps, all commands apply toPassport 7400, 8700, 15000.

1 Enter configuring mode.

start Prov

2 Configure the Passport FP to run IMA in a Passport shelf.

add Shelf Card/<Card>

where:<Card> is the instance number of the function processor providing IMAcapability.

3 Set the cardType attribute.

set Shelf Card/<Card> cardType <IMA_FP>

where:<IMA_FP> is the function processor supporting IMA. The values for<IMA_FP> are

• 8pDs1Atm for Passport 7400

• 8pE1Atm for Passport 7400

• 32pDs1Msa for Passport 7400

• 32pE1Msa for Passport 7400

• 32pDs1MsaMtp for Passport 7400



• 32pDs1MsaStp for Passport 7400

• 32pE1MsaMtp for Passport 7400

• 32pE1MsaStp for Passport 7400

• 4pDs3ChAtm for Passport 15000 and 20000

4 Configure a new logical processor type by adding aLogicalProcessorType (Lpt) component.

add Sw Lpt/imaFp

5 Configure the appropriate features on the Lpt component.

set Sw Lpt/imaFp featureList <feature>

where:<feature> is the name of the feature you want to set.

The applications that you plan to use determine what other features youmust add to the ImaFp featureList. For a complete list of applications andservice combinations on an imaFp, see the Release Notes.

6 Add a LogicalProcessor (Lp) component.

add Lp/<Lp>

where:<Lp> is the instance number of the logical processor associated with thefunction processor providing IMA capability.

7 Link the LogicalProcessor to the FP running IMA by setting the mainCardattribute.

Note: To facilitate node monitoring and troubleshooting, the instancenumber of the Lp and its associated Card component are usually set tothe same value.

set Lp/<Lp> mainCard Shelf Card/<Card>

8 Set the logicalProcessorType attribute of the Lp with the name of theappropriate Lpt component.

set Lp/<Lp> Lpt Sw Lpt/imaFp

9 Perform a semantic check on the configured data.

check Prov

10 Activate the configured data.

activate Prov

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Note: The editing view becomes the current view when this command isused.

11 Confirm the activation.

confirm Prov

Configuring the ports, IMA link groups, and independent linksPlease refer to the figure “IMA feature components and configurableattributes” (page 67), before performing the following procedures.

Ensure that you have performed the prerequisite tasks defined in“Configuring the Passport FP supporting the IMA feature” (page 77)

1 Add a port to the LogicalProcessor (Lp) component.

For Passport 7400 use the following command:

add Lp/<Lp> <port_type>/<port_number>

where:<Lp> is the instance number of the logical processor associated with thefunction processor providing IMA capability.<port_type> is Ds1 for an eight-port DS1 ATM FP and a 32-port DS1Multiservice Access FP, or E1 for an eight-port E1 ATM FP and a 32-portE1 Multiservice Access FP.<port_number> is the instance number of the port, having a valuebetween 0 and 7 inclusive, for an eight-port DS1/E1 ATM FP, or between0 and 31 inclusive for a 32-port DS1/E1 Multiservice Access FP.

For Passport 15000 or 20000, use the following command:

add Lp/<Lp_15000> DS3/<DS3_15000> DS1/<DS1_15000>

where:<Lp_15000> is the instance number of the logical processor associatedwith the function processor providing IMA capability.<DS3_15000> is the instance number of the DS3 port, having a valuebetween 0 and 3 inclusive.<DS1_15000> is the instance number of the DS1 tributary, having a valuebetween 1 and 28 inclusive.

2 For the 32-port DS1/E1 Multiservice Access FPs, add the AtmCell (Cell)component.

add Lp/<Lp_MSA32> <port_type>/<port_number> Chan/0Cell



where:<Lp_MSA32> is the instance number of the 32-port DS1 or E1Multiservice Access FP providing IMA capability.

Note: For the eight-port DS1/E1ATM FPs and the four-port DS3Ch ATMFP, a single channel, Chan/0, is automatically created with all availabletimeslots allocated. Use of Chan/0 (the default value) is recommendedeven though other values are allowed. These timeslots cannot bechanged and only one Channel subcomponent per port is permitted. Forthe 32-port DS1/E1 Multiservice Access FPs, you must configuretimeslots under the Channel component. See step 3 for the commandused to configure timeslots for the 32-port DS1/E1 Multiservice AccessFPs.

3 For the 32-port DS1/E1 Multiservice Access FPs, set the timeslots underthe Channel (Chan) component.

For the 32-port DS1 Multiservice Access FP:

set Lp/<Lp_MSA32> DS1/<port_number> Chan/0 timeslots !1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2122 23 24

For the 32-port E1 Multiservice Access FP:

set Lp/<Lp_MSA32> E1/<port_number> Chan/0 timeslots !1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 18 19 20 21 2223 24 25 26 27 28 29 30 31

4 Add an IMA link group to the Lp component.


add Lp/<Lp> Ima/<Ima>

where:<Ima> is the instance number of the IMA link group, having a value of 0to 7 inclusive for the eight-port DS1/E1 ATM FPs, or a value of 0 to 31inclusive for the 32-port DS1/E1 Multiservice Access FPs.

Note: For the eight-port DS1/E1 ATM FPs, if the perVcQueueInterfacesattribute under an LP’s Arc subcomponent is set to a non-zero value, thentraffic shaping (per-Vc queuing) is enabled. If traffic shaping is enabled onan LP, then the instances of IMA groups and independent links can havevalues from 0 to 3. If traffic shaping is disabled, then the instances of IMAlink groups and independent links can have values from 0 to 7.


add Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>

241-5701-730 5.1S1


where:<Ima_15000> is the instance number of the IMA link group, having avalue between 0 and 13.

5 Add a link (Link (Lk) component) to the IMA link group.

Note: For ease of configuring, monitoring and troubleshooting, each linknumber usually corresponds to the same port number.


add Lp/<Lp> Ima/<Ima> Lk/<Lk>

where:<Lk> is the instance number of the link and has a value of 0 to 31inclusivefor the eight-port DS1/E1 FPs and the 32-port DS1/E1 MultiserviceAccess FPs.

With the eight-port DS1/E1 ATM FPs, you may configure a total of eightlinks in an IMA link group, each having an instance number anywherebetween 0 and 31 inclusive. For example, an FP running IMA with a fullcomplement of eight links forming an IMA link group may include linkswith any combination of identifiers, such as:

• links 0, 1, 2, 3, 4, 5, 6, 7 or

• links 0, 5,14, 23, 24, 25, 27, 31

With the 32-port DS1/E1 Multiservice FPs, you can configure a total ofeight links in an IMA link group, with each link having an instance numberbetween 0 and 15 inclusive. Note that each IMA link group must beassociated with a port in the range 0 to 15 inclusive, or the range 16 to 31inclusive: all ports within an IMA link group must fall within one of thesetwo ranges. An IMA link group can include links 30 and 31 if the link groupinstance number (Ima component instance number) is in the range 16 to29.


add Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000> Lk/<Lk_15000>

where:<Lk_15000> is the instance number of the link and has a value of 0 to 31inclusive.

With Passport 15000 and 20000’s four-port DS3Ch ATM FP, you canconfigure upwards to a total of 28 links in an IMA link group, each havingan instance number anywhere between 0 and 31inclusive.



6 Associate each IMA link with the Channel (Chan) subcomponent of aport. Channel 0 is recommended even though other values are allowed.

For Passport 7400 use the following command. Repeat the command foreach IMA link.

set Lp/<Lp> Ima/<Ima> Lk/<Lk> interfaceName Lp/<Lp><port_type>/<port_number> Chan/0

Note 1: Each IMA link must be associated with a DS1or E1 physical link.

Note 2: No more than one link can be associated with any port.

Note 3: No more than one port can be associated with any link.

For Passport 15000 or 20000, use the following command. Repeat thecommand for each IMA link.

set Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000> Lk/<Lk> interfaceName Lp/<Lp_15000> DS3/<DS3> DS1/<DS1>chan/0

Note 1: Each IMA link must be associated with one DS1 logical link.

Note 2: An Ima link group under a DS3 port must be linked to a DS1 linkunder the same DS3 port: it cannot be linked to a DS1 link under anotherDS3 port.

Note 3: No more than 28 links can be associated with any port.

Note 4: No more than one port can be associated with any link.

7 Set the IMA protocol attribute.


set Lp/<Lp> Ima/<Ima> protocol <type>

where:<type> is the IMA protocol. For the eight-port DS1/E1 ATM FPs, it canhave values of either atmForum10 or proprietary. For the 32-port DS1/E1ATM FPs, the value is atmForum10.

Note 1: The eight-port DS1/E1 ATM FPs supports both the ATM ForumIMA protocol and the proprietary IMA protocol. The 32-port DS1/E1Multiservice Access FPs support only the ATM Forum IMA protocol.

Note 2: When using the eight-port DS1/E1 ATM FPs, you must firstconfigure the IMA protocol feature, choosing between the ATM ForumIMA protocol or the proprietary IMA protocol feature.

241-5701-730 5.1S1


Note 3: To use the proprietary protocol when using the eight-port DS1/E1 ATM FPs, the Ima feature must be in the feature list for the LP. See theprocedure “Configuring the Passport FP supporting the IMA feature”(page 77).

Note 4: When using the eight-port DS1/E1 ATM FPs, if one or more IMAgroups under the LP will use the proprietary IMA protocol, then choosethe ima feature. The ATM Forum IMA protocol is also available if youchoose the ima feature. However, the ima feature consumes morememory on the FP than the ImaAtmForum feature since it also supportsthe proprietary IMA protocol.


set Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>protocol atmForum10

Note: The Passport 15000 and 20000 four-port DS3Ch ATM FP supportonly the ATM Forum IMA protocol. The default setting for all Passport FPssupporting IMA is atmForum10.For more information, see“IMA protocols”(page 30).

8 Set the IMA transmitClockMode attribute.

Note 1: The CTC mode is available only on the ATM Forum IMA protocoland is supported by on the eight-port DS1/E1 ATM FPs and the 32-portDS1/E1 Multiservice Access FPs.

Note 2: If you are using eight-port DS1/E1 ATM FPs, use ITC mode if youhave selected the proprietary protocol or if the links in the IMA link groupdo not all use transmit clocking sources derived from the same reference.

Note 3: If you are using the ATM Forum IMA protocol on the eight-portDS1/E1 ATM FPs or the 32-port DS1/E1 Multiservice Access FPs, useCTC mode if all the links in a group use transmit clocking sources derivedfrom the same reference.

Note 4: The default value is itc for all Passport function processors.


set Lp/<Lp> Ima/<Ima> transmitClockMode <mode>

where:<mode> is the is the clock mode setting. If you have configured the eight-port DS1/E1 ATM FPs or the 32-port DS1/E1 Multiservice Access FPsusing the ATM Forum IMA protocol, you can set the mode clock setting aseither ctc or itc. If you have configured the eight-port DS1/E1 ATM FPsusing the proprietary IMA protocol is configured, you must set the clockmode setting to itc.

For Passport 15000 or 20000, use the following command.



set Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>transmitClockMode <mode_15000>

where:<mode_15000> is the is the clock mode setting which can have twovalues:itc for independent transmit clock modectc for common transmit clock mode

9 Set the IMA link group attributes as required (optional).

See 241-5701-060 Passport 7400, 15000, 20000 Components for furtherinformation concerning the attributes of the Ima component.

For Passport 7400 use the following command. Repeat the command foreach attribute you wish to add.

set Lp/<Lp> Ima/<Ima> <Ima_attribute><attribute_value>

where:<Ima_attribute> is the name of the Ima component attribute.<attribute_value> is the value of the Ima component attribute

For Passport 15000 or 20000, use the following command. Repeat thecommand for each attribute you wish to add.

set Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000><Ima_attribute> <attribute_value>


check Prov


activate Prov


confirm Prov

Configuring the ATM interface and linking it to an IMA linkgroup or an independent link

Please refer to the figure “IMA feature components and configurableattributes” (page 67), before performing the following procedures.

Unless otherwise specified in the following steps, all commands apply toPassport 7400, 8700, 15000.

241-5701-730 5.1S1


1 Add an ATM interface for each IMA link group.

Note: An AtmIf component is configured for each ATM interface. Itmanages the set of ATM connections that terminate or traverse theinterface. For more information, see 241-5701-700 Passport 7400,15000, 20000 ATM Overview.


add AtmIf/<AtmIf>

where:<AtmIf> is the instance of the AtmIf component using a particular IMAlink group and it can be any number between 1 and 1 024.


add AtmIf/<AtmIf_15000>

where:<AtmIf_15000> is the instance of the AtmIf component using aparticular IMA link group and it can be any number between 1 and 65 535.

2 Link each IMA link group to an ATM interface.


set AtmIf/<AtmIf> interfaceName Lp/<Lp> Ima/<Ima>

where:<Lp> is the instance number of the logical processor associated with thefunction processor providing IMA capability.<Ima> is the instance number of the IMA link group, having a value of 0to 7 inclusive for the eight-port DS1/E1 ATM FPs, or a value of 0 to 29inclusive for the 32-port DS1/E1 Multiservice Access FPs.


set AtmIf/<AtmIf_15000> interfaceName Lp/<Lp_15000>DS3/<DS3_15000> Ima/<Ima_15000>

where:<Lp_15000> is the instance number of the logical processor associatedwith the function processor providing IMA capability.<DS3_15000> is the instance number of the DS3 port, having a valuebetween 0 and 3 inclusive.<Ima_15000> is the instance number of the IMA link group, having avalue between 0 and 13.

3 Link each independent link to an ATM interface.



or

Note: The instance numbers of IMA link groups and independent linksmust be unique in a mixed configuration (The independent link instancenumber is the same as the DS1 or E1 subcomponent).


set AtmIf/<AtmIf> interfaceName Lp/<Lp> <port_type>/<port_number> Chan/0

where:<port_type> is Ds1for an eight-port DS1 ATM FP and a 32-port DS1Multiservice Access FP, or E1 for an eight-port E1 ATM FP and a 32-portE1 Multiservice Access FP.<port_number> is the instance number of the port, having a valuebetween 0 and 7 inclusive, for an eight-port DS1/E1 ATM FPs, or between0 and 31 inclusive for a 32-port DS1/E1 Multiservice Access FPs.


set AtmIf/<AtmIf_15000> interfaceName Lp/<Lp_15000>DS3/<DS3_15000> DS1/<DS1_15000> Chan/0


check Prov


activate Prov

Note: The editing view becomes the current view when this command isused.


confirm Prov

Migrating software releasesWhen you are migrating from Passport release 4.1 or 4.2 to release 5.0beyond, the procedure adds the new provisionable attributesprotocol andtransmitClockModeto existingImacomponents.To ensure that compatibilityis maintained with the existing configuration, theprotocol attribute isautomatically set to proprietary and thetransmitClockMode attribute isautomatically set to itc.

241-5701-730 5.1S1


M

anhe

”

es at

Upgrading IMA groups to the ATM Forum IMA protocolThis section provides the steps to upgrade on the eight-port DS1/E1 ATFPs, an existing IMA link group from the proprietary IMA protocol to theATM Forum IMA protocol. It includes the following procedures:

• “Upgrading an existing IMA link group on the eight-port DS1/E1 ATMFPs” (page 87)

• “Re-configuring the IMA software features list” (page 88)

This is an optional procedure that you can use when all the IMA linkgroups on the FP are using the ATM Forum protocol. This procedure cbe used to free memory if the proprietary protocol is not required on tFP.

Note:The 32-port Multiservice Access FPs and the four-port DS3ChATM FPs support only the ATM Forum protocol. See “IMA protocols(page 30) for additional information on IMA protocols on Passport.

Upgrading an existing IMA link group on the eight-port DS1/E1 ATM FPs

Ensure that you have Passport release 5.0 or beyond software on the nodboth ends of the IMA link group.


start Prov

2 Change the setting of the Ima component protocol attribute toatmForum10 at both ends of the IMA link group.

set Lp/<Lp> Ima/<Ima> protocol atmForum10

Note: This step is a component critical change that causes the IMA linkgroup to go out of service during the change-over.

where:<Lp> is the instance number of the logical processor associated with thefunction processor providing IMA capability.<Ima> is the instance number of the IMA link group, having a value of 0to 7 inclusive for the eight-port DS1/E1 ATM FPs.


check Prov



es at

4 Save the new view to disk.

save Prov


activate Prov

This IMA link group is now operating with the ATM Forum protocol.


confirm Prov

7 Repeat this procedure for any other IMA link groups on the FP.

Re-configuring the IMA software features listEnsure that you have Passport release 5.0 software or beyond on the nodboth ends of the IMA link group.


start Prov

2 Ensure that other FPs are not using the LPT that you are about to re-configure.

3 When all IMA groups on an FP are using the ATM Forum protocol, re-configure the IMA feature selected on the LPT at both ends of the IMA linkgroup.

set Sw Lpt/imaFp featureList ~ima imaAtmForum

Configuring the feature list to use the imaAtmForum feature avoidsloading unnecessary software on the FP and results in memory savings.

Note: When this configured change is activated, the FP is reset to purgeunnecessary software from memory.


check Prov


activate Prov


confirm Prov

241-5701-730 5.1S1

89

n ofsetor

ort’scal

on

Chapter 4IMA feature monitoring

This section provides procedures that you can use to monitor the conditioyour IMA application on Passport 7400, 15000, 20000. It describes how toand interpret the operational attributes available with IMA components. Fmore complete information on IMA components and attributes, see241-5701-060Passport 7400, 15000, 20000 Components.

The procedures shown in this section are intended to be used with Passpcomponent administration system (CAS) and may be performed using a loVT100 terminal or a remote connection (such as telnet). For informationhow to use the Preside Multiservice Data Manager graphical interface tomonitor Passport features and services, see 241-6001-023Preside MDMConfiguration Management for Passport User Guide.

This section specifically provides information on:

• “How to monitor services and features on Passport” (page 90)

• “OSI management states” (page 90)

• “IMA components and operational attributes” (page 91)

• “Internal diagnostics” (page 93)

• “Maintenance tests” (page 95)

• “Monitoring the status of the IMA application” (page 99)

• “Monitoring the status of a Link” (page 100)

• “Determining if the IMA group is active” (page 103)

• “Determining the active links in an IMA group” (page 105)


90 Chapter 4 IMA feature monitoring

that

and

ility,

d ifage

• “Monitoring IMA capacity and utilization” (page 107)

• “Monitoring relative link delays” (page 109)

• “Determining remote link configuration” (page 110)

• “Determining if the IMA group provides adequate bandwidth”(page 111)

How to monitor services and features on PassportTo monitor Passport features, you need to use either thelist or displaycommand. See 241-5701-050Passport 7400, 15000, 20000 Commands fordetails on how to monitor services and features on a Passport node.

OSI management statesAlmost every operational component in Passport has a set of attributes indicates its OSI management state. The OSI management state of acomponent indicates key aspects of a component’s usability, operability,availability at any given time.

Note:Not all components support all possible OSI attribute values.

The three primary factors affecting the state of a component are operabusage and administration:

• Operability indicates whether or not a component is installed andworking. The two possible operational states of a component are:

— disabled

— enabled

• Usage indicates whether or not the component is actively in use, anso, whether or not it has spare capacity for additional users. The usstate attribute has one of three possible values:

— idle

— active

— busy

241-5701-730 5.1S1

Chapter 4 IMA feature monitoring 91

e.e

thehe

• Administration indicates what permissions and prohibitions are in placThis state is imposed through the management system and has threpossible values:

— locked

— unlocked

— shutting down

IMA components and operational attributesThe IMA feature components and operational components are shown infigure “IMA feature components and operational attributes” (page 92). TIma subcomponents of theLp component and theLp DS3subcomponentpermit access to an IMA group and contains a number of operationalattributes.Link andTest are sub-components of theLp Ima andLp DS3 Imasubcomponents. The figure also shows the operational attributes of theImasubcomponent of theLp component. A complete listing of the Ima featureattributes are in 241-5701-060Passport 7400, 15000, 20000 Components.



Figure 18IMA feature components and operational attributes


Link (Lk)

DS1

DS3

LogicalProcessor (Lp)

EM


E1

Test (Test)type (type)

Componentattribute

failureCause (cause)remoteDefect (remDef)remoteLidsConfig (remConf)remoteLidsActive (remAct)cellCapacity (cap)remoteGid (remGid)

failureCause (cause)remoteDefect (remDef)remoteLid (remLid)relativeDelay (rel)lastOifCause (oif)

Link (Lk)

Test (Test)See attributes listing under Lp Ima Test

receiveCellUtilization (rxutil)transmitCellUtilization (txutil)

idleCellSec (idle)

See attributes listing under Lp Ima

See attributes listing under Lp Ima Lk

DS1

241-5701-730 5.1S1


ock

oftuptive

c

l

)

Internal diagnosticsYou may want to lock either a port orIma component to temporarilydiscontinue active service of the component. Whenever you attempt to unla port orIma component, some internal diagnostics (self-tests) areautomatically performed. If the diagnostics pass, the administrative statethe component changes from locked to unlocked and the port or IMA starprocedure is executed. If the diagnostics fail, the component’s administrastate remains locked and the test failure result is returned in an alarm.

Note: If you lock a DS1 or E1 port that is actively part of an IMA linkgroup, and if you have sufficient bandwidth, you will not lose user traffiif you are running the ATM Forum IMA protocol. However, if you areusing the proprietary IMA protocol on the eight-port DS1/E1 DS1/E1ATM FPs, and you lock a port in an IMA link group, you may briefly loseuser traffic.If you lock a DS3 port on the four-port DS3Ch ATM FP, you will lose alindependent links and IMA link groups under that DS3 port.

• the procedure “Locking and unlocking a port component” (page 93)shows how to lock and unlock aPort component

• the procedure “Locking and unlocking an IMA component” (page 94shows how to lock and unlock anIma component.

Locking and unlocking a port component1 Lock a port component.

For Passport 7400 use the following command to lock a DS1 or E1component:

lock Lp/<Lp> <port_type>/<port_number>

where:<Lp> is the instance number of the logical processor associated with thefunction processor providing IMA capability.<port_type> is Ds1for an eight-port DS1 ATM FP and a 32-port DS1Multiservice Access FP, or E1 for an eight-port E1 ATM FP and a 32-portE1 Multiservice Access FP.<port_number> is the instance number of the port, having a valuebetween 0 and 7 inclusive, for an eight-port DS1/E1 ATM FP, or between0 and 31 inclusive for a 32-port DS1/E1 Multiservice Access FP.



For Passport 15000 or 20000, use the following command to lock a DS3port:

lock Lp/<Lp_15000> DS3/<DS3_15000>

where:<Lp_15000> is the instance number of the logical processor associatedwith the function processor providing IMA capability.<DS3_15000> is the instance number of the DS3 port, having a valuebetween 0 and 3 inclusive.

For Passport 15000 or 20000, use the following command to lock a DS1tributary component of a channelized DS3 port:

lock Lp/<Lp_15000> DS3/<DS3_15000> DS1/<DS1_15000>

where:<DS1_15000> is the instance number of the DS1 tributary, having a valuebetween 1 and 28 inclusive.

2 Unlock a port component.

For Passport 7400 use the following command to unlock a DS1 or E1component:

unlock Lp/<Lp> <port_type>/<port_number>

For Passport 15000 or 20000, use the following command to unlock aDS3 port:

unlock Lp/<Lp_15000> DS3/<DS3_15000>

For Passport 15000 or 20000, use the following command to unlock aDS1 tributary component of a channelized DS3 port:

unlock Lp/<Lp_15000> DS3/<DS3_15000> DS1/<DS1_15000>

Locking and unlocking an IMA component1 Lock an Ima component.


lock Lp/<Lp> Ima/<Ima>


241-5701-730 5.1S1


he

ted

the


lock Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>


2 Unlock an Ima component.


unlock Lp/<Lp> Ima/<Ima>


unlock Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>

Maintenance testsMaintenance testing is supported for the IMA application and for ports on tPassport FPs supporting the IMA feature. TheTestsubcomponent of theImacomponent controls maintenance testing for the IMA application.

Performing a manual test on the IMA componentA manual test is supported by theIma component. It requires the tester toexternally loop-back the transmit signal to the port’s receive path. A testpattern is generated at the transmit end of the IMA link group and distribuacross all active links for transmission. The receive end of the IMA linkrecombines the data from the active links into a single stream and verifiesresults of the transmission.

Note: If you are configuring a manual test, thetypeattribute for ports atthe remote end must be set toexternalLoop.

Please refer to the figure “IMA feature components and operationalattributes” (page 92), before performing the following procedures.

1 Identify the type of test to be executed on the local Ima component.

For Passport 7400, use the following command:



set Lp/<Lp> Ima/<Ima> Test type manual



set Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000> Testtype manual


2 Specify the external loop test type on the port at the remote end.

For a Passport 7400 DS1 port, use the following command:

set Lp/<Lp> DS1/<DS1> Test type externalLoop

For a Passport 7400 E1 port, use the following command:

set Lp/<Lp> E1/<E1> Test type externalLoop


set Lp/<Lp_15000> DS3/<DS3_15000> Test typeexternalLoop

where:<DS1> is the instance number of the DS1 port.<E1> is the instance number of the E1 port.

3 Make sure the duration of the remote-end port test is longer than thatconfigured for the IMA test. If necessary, set it to a new value.


set Lp/<Lp> DS1/<DS1> Test duration <limit>


set Lp/<Lp> E1/<E1> Test duration <limit>

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set Lp/<Lp_15000> DS3/<DS3_15000> Test duration<limit>

where:<limit> specifies the maximum length of time (in minutes) that the testcan run. The default value is 1.00.

4 Lock the port at the remote end.


lock Lp/<Lp> DS1/<DS1>


lock Lp/<Lp> E1/<E1>


lock Lp/<Lp_15000> DS3/<DS3_15000>

5 Complete step 2 through step 4 for all ports at the remote end for the IMAgroup.

Note: Test data is sent (shared) over all the links in the IMA group; if youdo not complete these step 2 through step 4 for all remote ports prior toinitiating the test then errors in the test occur.

6 Use the start command to initiate the test on the port at the remote end.


start Lp/<Lp> DS1/<DS1> Test


start Lp/<Lp> E1/<E1> Test


start Lp/<Lp_15000> DS3/<DS3_15000> Test

7 Complete step 2 through step 4 for all ports at the remote end for the IMAgroup. Test data is sent (shared) over all the links in the IMA group; if youdo not complete these steps for all remote ports then errors in the testoccur.

8 Lock the Ima component to be tested.


lock Lp/<Lp> Ima/<Ima>




lock Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>

9 Use the start command to invoke the test on the Ima component.


start Lp/<Lp> Ima/<Ima> Test


start Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>Test

10 Display the results of a test in progress.


display Lp/<Lp> Ima/<Ima> Test


display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>Test

11 If necessary, stop the test.

For Passport 7400, use the following command:

stop Lp/<Lp> Ima/<Ima> Test


stop Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>Test

12 Unlock the Ima component when the test is complete.


unlock Lp/<Lp> Ima/<Ima>


unlock Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>

13 If necessary, stop the test on the port at the remote end.


stop Lp/<Lp> DS1/<DS1> Test


stop Lp/<Lp> E1/<E1> Test

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stop Lp/<Lp_15000> DS3/<DS3_15000> Test

14 Unlock the port at the remote end when the test is complete.


unlock Lp/<Lp> DS1/<DS1>


unlock Lp/<Lp> E1/<E1>


unlock Lp/<Lp_15000> DS3/<DS3_15000>

Port testsFor details about port tests, see 241-5701-520Passport 7400, 15000, 20000Troubleshooting and Testing.

Monitoring the status of the IMA applicationThis procedure provides a command to display a list of operational attribuindicating the status of the IMA application. Some of the commandsdescribed elsewhere in this section show how to display the values ofindividual attributes that appear in this list.

Please refer to the figure “IMA feature components and operationalattributes” (page 92), before performing the procedure.

1 Use the display command to determine the operational attributes of theIMA application.


display Lp/<Lp> Ima/<Ima>



display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>



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Monitoring the status of a LinkThe procedure “Determining the status of an IMA link” (page 100) providea command to display a list of operational attributes indicating the status oLink subcomponent. Some of the commands described elsewhere in thisection show how to display the values of individual attributes that appeathis list.

The procedure “Determining the status of all links in an IMA group basedstatistical attributes” (page 101) provides a command to display the statuall links in an IMA group based on its statistical attributes.

The procedure “Determining the cause of the most recent OIF anomaly”(page 102) provides a command to display the cause of the most recent oIMA frame (OIF) anomaly.

The procedure “Determining the number of one-second intervals in whicidle cells were received” (page 102) provides a command to display thenumber of one second intervals in which one or more idle cells were receiv


Determining the status of an IMA link1 Use the display command to determine the operational attributes of the

link.


display Lp/<Lp> Ima/<Ima> Lk/<Lk>

where:<Lp> is the instance number of the logical processor associated with thefunction processor providing IMA capability.<Ima> is the instance number of the IMA link group, having a value of 0

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to 7 inclusive for the eight-port DS1/E1 ATM FPs, or a value of 0 to 29inclusive for the 32-port DS1/E1 Multiservice Access FPs.<Lk> is the instance number of the link and has a value of 0 to 31inclusivefor the eight-port DS1/E1 ATM FPs and the 32-port DS1/E1 MultiserviceAccess FPs.


display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>Lk/<Lk_15000>


Determining the status of all links in an IMA group based onstatistical attributes

1 Display the performance monitoring statistics provided for the links.

Note: Performance monitoring statistics are provided only if the ATMForum IMA protocol is being used.


display Lp/<Lp> Ima/<Ima> Lk/* statistics



display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>Lk/* statistics

where:<Lp_15000> is the instance number of the logical processor associatedwith the function processor providing IMA capability.<DS3_15000> is the instance number of the DS3 port, having a valuebetween 0 and 3 inclusive.



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llsring

<Ima_15000> is the instance number of the IMA link group, having avalue between 0 and 13.

Determining the cause of the most recent OIF anomalyWhen an OIF (out of IMA frame) anomaly occurs on a link, the attributevalue does not change until another OIF occurs with a different cause. TattributelastOifCause is not available with the proprietary protocol and isalways set tonoOif in this case.

1 Display the cause of the most recent out of IMA frame (OIF) anomaly.


display Lp/<Lp> Ima/<Ima> Lk/* lastOifCause



display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>Lk/* lastOifCause


Determining the number of one-second intervals in which idlecells were received

The idleCellSec attribute allows you to detect the presence of idle cells onlinks in an IMA link group. Otherwise, you may not be aware that idle ceare being generated. For example, idle cells may occur due to a configuerror in which links in CTC mode are deriving their clock source fromdifferent references. The attributeidleCellSec is not available with theproprietary IMA protocol, and is always set to “0” in this case.

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e

1 Use the display command to determine the number of one secondintervals in which one or more idle cells were received.


display Lp/<Lp> Ima/<Ima> Lk/* idleCellSec



display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>Lk/* idleCellSec


Determining if the IMA group is activeThis procedure provides commands to determine:

• whether or not the IMA group is active

• the cause of failure if the group is inactive

• the remote defect indicator being received from IMA application at thremote end


1 To determine whether or not the IMA group is active, use the command toexamine the operational state of the IMA component.

If the operational state is enabled, the group is active. If the operationalstate is disabled, the group is inactive.




display Lp/<Lp> Ima/<Ima> operationalState



display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>operationalState


2 If the IMA is disabled, you can use the display command to determine whythe group is inactive.


display Lp/<Lp> Ima/<Ima> failureCause


display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>failureCause

3 If the failure cause is due to a remote failure, you can use the displaycommand to examine the remote defect indicator received from theremote IMA.


display Lp/<Lp> Ima/<Ima> remoteDefect


display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>remoteDefect

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Determining the active links in an IMA groupThis section provides two commands to determine which links are activean IMA group. You can identify

• which local links are active, which ones have failed, and the cause ofailure (see the procedure “Determining the active and failed links inIMA group” (page 105))

• which remote links have been activated by the IMA application at thremote end, and which links have been configured by the IMAapplication at the remote end (see the procedure “Determining whiclinks in the IMA group are currently active and configured at the remoend” (page 106))


Determining the active and failed links in an IMA group1 Display the operational state of the Link subcomponents to determine

which links are active or failed.


display Lp/<Lp> Ima/<Ima> Lk/* operationalState



display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>Lk/* operationalState


2 Display the reason for a disabled condition of a link (link is inactive).




display Lp/<Lp> Ima/<Ima> Lk/<Lk> failureCause

where:<Lk> is the instance number of the link and has a value of 0 to 31inclusivefor the eight-port DS1/E1 FPs, or a value of 0 to 29 inclusive for the 32-port DS1/E1 Multiservice Access FPs.


display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>Lk/<Lk_15000> failureCause

where:<Lk_15000> is the instance number of the link and has a value of 0 to 31inclusive.

3 In the case where the failureCause is remoteFailure, display theremoteDefect indicator to see why a link is inactive.


display Lp/<Lp> Ima/<Ima> Lk/<Lk> remoteDefect


display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>Lk/<Lk_15000> remoteDefect

Determining which links in the IMA group are currently activeand configured at the remote end

1 Display the remoteLidsActive attribute of the Ima component to determinewhich links have been configured by the remote IMA.


display Lp/<Lp> Ima/<Ima> remoteLidsConfig



display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>remoteLidsConfig

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2 Display the remoteLidsActive attribute of the Ima component to determinewhich links have been activated by the remote IMA.


display Lp/<Lp> Ima/<Ima> remoteLidsActive


display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>remoteLidsActive

3 Display the remoteGid attribute of the Ima component to determine theIMA link group ID used by the remote IMA.


display Lp/<Lp> Ima/<Ima> remoteGid


display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>remoteGid

Note: The remoteGid attribute is supported only if the ATM Forum IMAprotocol is being used.

Monitoring IMA capacity and utilizationThe procedure “Determining the throughput available over an IMA group(page 108) provides a command to monitor the throughput capacity curreavailable over an IMA link group.

The procedure “Determining the current cell utilization of an IMA group”(page 108) provides a command to monitor the current cell utilization of IMA group as a percentage of the current capacity. Cell utilization is averagover a one-minute sliding window.




Determining the throughput available over an IMA group1 Use the display command to determine the throughput available over an

IMA group.

Total throughput over an IMA link is the sum of the throughput availableon each link, shown in cells per second.


display Lp/<Lp> Ima/<Ima> cellCapacity



display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>cellCapacity


Determining the current cell utilization of an IMA group1 Use the display command to determine the current cell utilization as a

percentage of the current capacity of an IMA group. (Utilization isaveraged over a one-minute sliding window.)


display Lp/<Lp> Ima/<Ima> receiveCellUtilization,transmitCellUtilization


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ee

ForPassport 15000 or 20000, use the following command:

display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>receiveCellUtilization, transmitCellUtilization


Note: The cell utilization attributes are supported only if the ATM ForumIMA protocol is being used. If the proprietary IMA protocol is being used,these attributes are always set to zero.

Monitoring relative link delaysThis procedure provides a command to display

• the link (or links) with the least delay in an IMA link group, and

• the last-measured delay of the remaining links relative to the link (orlinks) with the least delay in the group

Note:If connectivity to the remote link is not available (for example, duto a LIF, LCD, LOF or LOS or condition), the ICP cells cannot providthe correct values for theremoteDefect andremoteLid attributes. Thevalue for therelativeDelay attribute is meaningless when the link isdown.


1 Use the display command to determine the relative delay between eachof the links in an IMA group.


display Lp/<Lp> Ima/<Ima> Lk/* relativeDelay

where:<Lp> is the instance number of the logical processor associated with thefunction processor providing IMA capability.<Ima> is the instance number of the IMA link group, having a value of 0



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to 7 inclusive for the eight-port DS1/E1 ATM FPs, or a value of 0 to 29inclusive for the 32-port DS1/E1 Multiservice Access FPs.


display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>Lk/* relativeDelay


Determining remote link configurationThis procedure provides a command to display the logical link ID used byremote IMA for each link. Please refer to the figure “IMA feature componenand operational attributes” (page 92), before performing the procedure.

Note:If connectivity to the remote link is not available (for example, duto a LIF, LCD, LOF or LOS or condition), then theremoteLidhas a valueof 0.

1 Use the display command to determine the remote logical link ID of thelinks in an IMA group.


display Lp/<Lp> Ima/<Ima> Lk/* remoteLid



display Lp/<Lp_15000> DS3/<DS3_15000> Ima/<Ima_15000>Lk/<Lk_15000> remoteLid

where:<Lp_15000> is the instance number of the logical processor associatedwith the function processor providing IMA capability.

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<DS3_15000> is the instance number of the DS3 port, having a valuebetween 0 and 3 inclusive.<Ima_15000> is the instance number of the IMA link group, having avalue between 0 and 13.

Determining if the IMA group provides adequate bandwidthAn IMA link group may not always have enough bandwidth to support alATM connections associated with the ATM interface. When some physiclinks on the IMA group have failed, some bandwidth non-elastic connectiomay have to be released and some bandwidth elastic connections may hareduce their bandwidth consumption.

See 241-5701-708Passport 7400, 15000, 20000 ATM CAC and BandwidtManagement for details on

• dynamic bandwidth management for ATM connections

• how to monitor ATM connections and dynamic bandwidth



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Chapter 5Troubleshooting IMA

This section provides information on how to troubleshoot the IMA feature.contains the following sections:

• “Passport alarms” (page 113)

• “IMA-specific alarms” (page 115)

• “IMA link alarms” (page 117)

• “The troubleshooting process” (page 118)

• “Tools for troubleshooting IMA” (page 118)

• “Troubleshooting using Nortel Networks Preside Multiservice DataManager” (page 118)

• “Handling problems” (page 119)

Passport alarmsOn-switch alarms are generated asynchronously by Passport componentare displayed on the user interface to indicate faults or failure conditions oPassport node. When an alarm occurs, it indicates that a component neebe serviced or that it has detected a fault elsewhere on the node. Alarmdescriptions contain information to assist you in monitoring andtroubleshooting your Passport network. Alarms specifically indicate one the following:

• degradation/quality-of-service conditions

(for example, when a threshold is reached)


114 Chapter 5 Troubleshooting IMA

ataer

the

• processing error

(for example, protocol violations)

• failures/out-of-service conditions

(for example, hardware failures)

• administrative conditions

(for example, issuing the lock command)

• security violations

The interface can be either a VT100 terminal or a Preside Multiservice DManager workstation. For information on Preside Multiservice Data Managtools, see 241-6001-023Preside MDM Configuration Management forPassport User Guide.

Alarms contain information that can assist you in monitoring the node andnetwork. The figure “Example of an IMA alarm appearing on the textinterface” (page 114) provides an example of an alarm. For completeinformation on Passport alarms, see 241-5701-500Passport 6400, 7400,15000, 20000 Alarms.

Figure 19Example of an IMA alarm appearing on the text interface

Lp/1 Ima/2 Lk/11; 1998-03-20 14:19:40.08SET critical communicationscommProtocolError 7011 1210

ADMIN: unlocked OPER: disabled USAGE: idleAVAIL: PROC: CNTRL:ALARM: critical STBY: notSet UNKNW: falseId: 01000064 Rel:Com: Loss of Ima Framing (LIF) has been detected.

Check the last OIF cause of the link.Int: 1/0/2/8499; ImaAFLinkHandler_Actor.cc; 2202; p5.0d.30

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Chapter 5 Troubleshooting IMA 115

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IMA-specific alarmsPassport alarms indicating the following state changes can be generateIMA feature.

Note:The text “(A)” denotes that the alarm applies only to the ATMForum IMA protocol. The text “(p)” denotes that the alarm applies onto Passport’s proprietary IMA protocol. If no text qualifier is providedthen the alarm applies to both the ATM Forum and proprietary IMAprotocols.

• 7011 1100 - IMA group failure. There are no links active in the group

• 7011 1210 (A) - IMA link failure. A loss of IMA frame (LIF) defect hasoccurred on a link.

• 7011 1211 (A) - IMA link failure. The link is experiencing a loss of delaysynchronization (LODS) condition.

• 7011 1212 (A) - IMA link failure. The link has been misconnected.

• 7011 1213 (A) - IMA link failure. The system has detected a remotefailure indicator (RFI) alarm condition.

• 7011 1214 (A) - IMA link failure. The system has detected a fault alarcondition on the link.

• 7011 1215 (A) - IMA link failure. The remote link has gone into anunusable state.

• 7011 1216 (A) - IMA link failure. The system has detected a protocoerror alarm condition on the link

• 7011 1200 (p) - IMA link failure. The link is not active in the group.

For details on these alarms, see 241-5701-500Passport 6400, 7400, 15000,20000 Alarms.

IMA group alarmsIMA group alarms are set and cleared in response to conditions causinggroup to go out of service. There is one alarm at the IMA group level(7011 1100).



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When the ATM Forum IMA protocol is used, the alarm text provides anindication of the cause of the alarm. The following are potential causes:

• The IMA group IDs received in the ICP cells on all candidate links(remaining after the transmit test procedure) involved in IMA groupstart-up do not match.

• The IMA frame lengths received in the ICP cells on all candidate linkinvolved in IMA group start-up do not match the value supported by thIMA group. (Passport IMA supports only a frame length of 128.)

• The logical link IDs received in the ICP cells on all candidate links(remaining after the transmit test procedure) involved in IMA groupstart-up are not unique.

• The IMA group symmetry received in the ICP cells on all candidate linkinvolved in IMA group start-up is not supported. (Passport IMA supporonly symmetrical configuration.)

• An expected state transition expected from the far end did not take plduring IMA group start-up.

• The far end rejects the IMA frame length being used by the near enduring IMA group start-up.

• The far end rejects the group symmetry being used by the near end duIMA group start-up.

• The far end aborts for a reason other than bad frame length or symmduring IMA group start-up.

• No links can be activated during IMA group start-up, or the number active links is reduced to zero during normal operation.

• During IMA group start-up, or in normal operation, the Group Statusfield in ICP cells received on candidate or active links indicates that remote IMA has insufficient links.

• The far end enters start-up while the near end is not in start-up and unlocked.

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IMA link alarmsIMA link alarms are set and cleared in response to conditions causing theto go out of service. Some link alarms are set immediately when an errocondition is detected and cleared immediately when the error condition islonger present. Other link alarms are set when a defect is present for a peof time. These alarms are cleared when the defect is absent for a periodtime. In some cases, intermittent defects can also lead to alarms.

Link alarms for the proprietary IMA protocolThere is one alarm at the IMA link level when the proprietary IMA protocois being used for the IMA application on the eight-port DS1/E1 ATM functioprocessors. This alarm can be set for any of the following reasons:

• An IMA link-level problem occurs that results in loss of IMA frame(LIF) on the link.

• Unacceptable differential delay on the link that results in a loss of delsynchronization (LODS) condition.

• An IMA protocol error occurs. For example, the error can be invalidvalues for IMA ID, logical link ID, IMA frame length, or a time-outduring the IMA startup or link addition handshaking procedure.

• The link is rejected by the remote end.

Link alarms for the ATM Forum IMA protocolA number of alarm types are defined at the IMA link level when the ATMForum IMA protocol is being used on Passport. These alarm types are

• loss of IMA frame (LIF) defect on the link

• loss of delay synchronization (LODS) on the link

• the link is misconnected

• remote failure indicator (RFI) condition has occurred

• a fault condition has occurred indicating an invalid value

• remote link is unusable

• protocol error has occurred on the link



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The troubleshooting processThe objective of effective troubleshooting is to

• identify the problem quickly

• isolate the cause

• resolve the fault as quickly as possible in order to minimize disruptionservice or loss of data

A summary of troubleshooting actions is summarized in the remainder of tsection.

Tools for troubleshooting IMAYou can perform a manual external loopback test on theImacomponent. Forinstructions on performing this test, see “Performing a manual test on thIMA component” (page 95). You can also monitor the condition of your IMAapplication on Passport by performing a number of other commands (se“IMA feature monitoring” (page 89) for details).

You can avoid having to manually set up the external loopback for an IMtest by using the following steps:

1 Perform the external loopback test on the port components at the remend. For instructions, see 241-5701-520Passport 7400, 15000, 20000Troubleshooting and Testing.

2 Perform the IMA test. See “Performing a manual test on the IMAcomponent” (page 95).

Troubleshooting using Nortel Networks PresideMultiservice Data Manager

Nortel Networks Preside Multiservice Data Manager offers a comprehensset of fault management tools for detecting and isolating problems. Wheusing Preside Multiservice Data Manager to troubleshoot the IMA featuruse the integrated alarms display to view alarms and the integrated commconsole for access to IMA operational attributes.

For details on the scope and use of Preside Multiservice Data Managerinterface and software tools, see 241-6001-023Preside MDM ConfigurationManagement for Passport User Guide.

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Handling problemsThe table “Handling problems” (page 119) provides guidelines on how torespond to problems that may occur with an IMA application. Problems thoccur when your IMA application is operating may not be confined to IMcomponents only.

Note:The text “(A)” denotes that an alarm or value applies only to thATM Forum IMA protocol. The text “(p)” denotes that an alarm or valueapplies only to Passport’s proprietary IMA protocol. If no text qualifieis provided, then an alarm or value applies to both the ATM Forum aproprietary IMA protocols.

Table 7Handling problems

Problems that may occur Probable causes Corrective measures

IMA group alarm is set7011 1100

Value indicated for failureCauseattribute of the Ima component:

noGoodLinksInStartup - No linkscould be activated during IMAgroup startup

Check the operationalattributes of the Linksubcomponents. Ensure thatthe associated physical portsare enabled. Verify that theyare connected to ports beingused by a properly configuredremote IMA group.

badGidInStartup - Different groupIDs were received from the remotelinks during IMA group startup

Ensure that the links in thegroup are connected to linksunder a single remote Imacomponent.

badLidInStartup - Duplicate logicallink IDs were received from theremote links during IMA groupstartup

Ensure that the links in thegroup are connected to linksunder a single remote Imacomponent.

(Sheet 1 of 11)



unsupportedFrameLengthInStartup - An IMA frame length other than128 cells was received from one ormore of the remote links duringIMA group startup (p)

An IMA frame length other than128 cells was received from all ofthe remote links during IMA groupstartup (A)

Ensure that the remote IMAgroup uses a frame lengthsupported by your local IMAgroup.

timeoutInStartup - The remoteIMA application failed to enter IMAstartup within the expectedamount of time

Examine the operationalattributes of the remote Imacomponent. Ensure that thecomponent is not locked andthat its associated ports areenabled.

Note: Often the remoteDefectattribute of the Ima componentprovides an indication of thecause of failure at the remoteend; however, under somecircumstances this defectindicator cannot be received,so it is always best to examinethe remote end directly.

noGoodLinks - The group wasactive, but all links have becomedisabled (p)

All links have become disabled orfailed to become enabled while theIMA group was not in startup state(A)

Check the operationalattributes of the Linksubcomponents. Ensure thatthe associated physical portsare enabled. Examine theoperational attributes of theremote Ima component todetermine if it has caused theproblem.

Table 7 (continued)Handling problems


(Sheet 2 of 11)

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remoteFailure - The Imacomponent at the remote end hasa problem

Examine the operationalattributes of the remote Imacomponent.

Note: The remoteDefectattribute of the Ima componentoften provides an indication ofthe cause of failure at theremote end; however, undersome circumstances this defectindicator cannot be received,so it is always best to examinethe remote end directly.

unsupportedSymmetryInStartup

- The symmetry proposed by thefar end IMA group is not supportedon the local IMA group. Thisoccurs when the local IMA group isrunning ATM Forum protocol andthe far end proposes a groupsymmetry other than “symmetricconfiguration and operation” (A)

Ensure that the remote IMAgroup uses a group symmetrysupported by your local IMAgroup.

- The far end IMA group is usingproprietary protocol

Reprovision the far-end IMAgroup to use the ATM Forumprotocol.

IMA link alarm is set7011 1200 (p), or the Linkcomponent is disabled

If the value of the availabilityStatusattribute of the Link component isdepend and the physical interfaceis out of service (theoperationalState attribute of theChan component being used bythe link is disabled)

Correct the problem that hascaused the physical interface togo out of service. See theprocedures for troubleshootingproblems with functionprocessors in 241-5701-520Passport 7400, 15000, 20000Troubleshooting and Testing.



(Sheet 3 of 11)



If the availabilityStatus of the Linkcomponent is offLine, the parentIma component is locked(adminState attribute of the Imacomponent is “locked”)

Unlock the parent Imacomponent

Value indicated for failureCauseattribute of the Link component:

interfaceDown - The physicalinterface is out of service.

Correct the problem that hascaused the physical interface togo out of service or becomeunusable. See the proceduresfor troubleshooting problemswith function processors in241-5701-520 Passport 7400,15000, 20000 Troubleshootingand Testing.

lif - The link is in a “loss of IMAframe” state.

Check the cabling at theassociated port to ensure that itis properly connected to a portassociated with a Linkcomponent on the remote IMAgroup. Then, check the statusof the remote port to see if it isenabled.



(Sheet 4 of 11)

241-5701-730 5.1S1


lods - The differential delay of thislink exceeds the configured valuefor the maxDiffDelay attribute forthe Ima component given itsconfigured linkSelectionCriterionattribute

Display the relativeDelayoperational attributes of all theLinks under the Ima componentto determine their differentialdelays relative to the link withthe least delay.

If the provisioned maxDiffDelayattribute is not at its maximumvalue and an increasedtransmission delay can betolerated, increase the value ofthe maxDiffDelay attribute toactivate this link.

Otherwise do one of thefollowing:

• Remove one or more of theother links from the group toreduce the differential delayof this link such that it isactivated.

• Replace the physical facilityused by this link with oneexhibiting a lower differentialdelay.



(Sheet 5 of 11)



protocolError - A violation of theIMA startup or link additionprotocol occurred which preventedthis link from being activated

If the operationalState attributeof the parent Ima component isdisabled, the problem occurredduring group startup. Examinethe operational attributes of theIma component to troubleshootthe problem.

If the operationalState attributeof the parent Ima component isenabled, the problem occurredduring link addition. A fault mayhave occurred with the IMAgroup ID, frame length, orlogical link ID received on thislink, or the remote IMAapplication may not beresponding to attempts to addthis link.

Check the cabling at theassociated port to ensure that itis correctly connected to a portassociated with a Linkcomponent on the remote IMAgroup. Then, check the statusof the remote port to ensurethat it is enabled.



(Sheet 6 of 11)

241-5701-730 5.1S1


remoteFailure - The Linkcomponent at the remote end hasa problem

Examine the operationalattributes of the correspondinglink at the remote end totroubleshoot its problem.

Note: Often the remoteDefectattribute provides an indicationof the cause of failure at theremote end; however, undersome circumstances this defectindicator cannot be received,so it is always best to examinethe remote end directly.

IMA link alarm is set7011 1210 (A)

The alarm is due to a loss ofIMA frame (LIF) failure

The link is incorrectly connected orincorrectly configured.

Check the lastOifCauseoperational attribute of the linkto obtain an indication of thecause of the problem.

Check that the physical port isproperly connected at the localand remote ends and that allport alarms are clear.

Check the configuration of theLink components on the localand remote ends.



(Sheet 7 of 11)




A loss of delaysynchronization (LODS)condition is present on thelink.

The transit delay experienced onthe link is such that the link is nolonger in link delaysynchronization (LDS).

Check the relativeDelayoperational attribute of the linkto determine its differentialdelay. If an increase in themaximum differential delayacross the IMA group isacceptable, increase thesetting of the maxDiffDelayattribute of the parent Imacomponent.

Alternatively, change thesetting of thelinkSelectionCriterion attributeof the parent Ima componentThis may force the IMA groupto select a different referencelink.

Note: This action may causeother links to experience anLODS condition.

If the problem persists, replacethe physical facility used by thislink with one that has a transitdelay closer to that of thereference link.


The link is misconnected.

The link is incorrectly connectedor incorrectly configured.

Check that the physical port isproperly connected at the localand remote ends.




(Sheet 8 of 11)

241-5701-730 5.1S1



A remote failure indicator(RFI) alarm condition hasoccurred.

The remote IMA link hasexperienced a persistent defect.


Display the operationalattributes of the remote IMALink component.


A fault alarm condition hasoccurred on the link.

The link is incorrectly connectedor incorrectly configured.

Check that the physical port isproperly connected at the localand remote ends.

Check the failureCauseattribute of the IMA Linkcomponents.



The remote link has gone tothe unusable state.

The remote IMA link has gone tothe Unusable state. (For example,the remote port is down.)

Display the operationalattributes of the Linkcomponent at the remote endto determine why the link hasentered the unusable state.


A protocol error alarmcondition has occurred onthe link. The link could notbe activated within theprescribed time-out period.

The remote link is not changingstate as quickly as the local link.

Display the operationalattributes of the remote IMALink component.




(Sheet 9 of 11)



Occasional loss of traffic butno alarms issued

If certain Cell statistics (such asuncorrectableHecErrors) or Portstatistics (such as sevErroredSec)are increasing, this indicates aproblem with the physical facilityconnecting the near-end and far-end IMA groups. (For moreinformation about these statistics,see 241-5701-060 Passport 7400,15000, 20000 Components.)

Verify the physical linksconnecting the two IMA groupsand replace them if they are notproviding the required quality.

Do a port test on the local andremote ends to determine ifthere is any faulty equipmentand replace a card if required.

If the idleCellSec operationalattribute of an IMA Linkcomponent is increasing, thismeans that idle cells are beingreceived on the link.

Check the IMA clocking modeat the far-end and the clocksources for the physical portsthat are part of the IMA group.

Display theclockingModeMismatchoperational attribute of the IMALink. If its value is on, thismeans that both ends of theIMA group are not using thesame clocking mode. Althoughthis is a valid configuration,ensure that this is the expectedresult.

Ensure that there is a bittransparent link to the remoteIMA. For example, if the twoIMA groups are connectedthrough a cell-relay network,this will cause idle cells to beinserted.

Check the equipment at the far-end.



(Sheet 10 of 11)

241-5701-730 5.1S1


If one of the icpViolations,sevErroredSec, or unavailSecoperational attributes of an IMALink component is increasing, thismeans that the link is occasionallylosing IMA framing.

Check the lastOifCauseattribute of the IMA Linkcomponents.

Do an Ima loopback test onlocal and remote IMA groups todetermine if there is faultyequipment and replace a card ifrequired. (See “Performing amanual test on the IMAcomponent” (page 95).)

When one physical link goesout of service, it causes twoIMA links to go down.

The transmit and receive wires ofa port are not connected to thesame port at the remote end.

Display the remoteLidoperational attribute of the IMAlinks at both ends. Make surethe values match the expectedones.

IMA link states are going upand coming downrepeatedly.

Some link states areincorrect (either down ordisabled).

The number of links has exceededthe total number of links allowedfor each port block/port grouping.

Reconfigure the total number oflinks so that they are less thanor equal to the total number oflinks allowed per maker/portgrouping.

Note: The text “(A)” denotes that an alarm or value applies only to the ATM Forum IMA protocol.The text “(p)” denotes that an alarm or value applies only to Passport’s proprietary IMA protocol.If no text qualifier is provided, then an alarm or value applies to both the ATM Forum andproprietary protocols.



(Sheet 11 of 11)



241-5701-730 5.1S1

131

for

in).

ens

t

ith

AppendixPassport IMA compliance to specification

This section identifies certain exceptions to full specification complianceinverse multiplexing for ATM (IMA) on Passport. The specification for theIMA feature is the ATM Forum AF-PHY-0086.000,Inverse Multiplexing forATM (IMA) Specification, Version 1.0

IMA on Passport fully complies with all mandatory requirements of the ATMForum IMA Specification with the exception of the specific sections listedthe table “Passport IMA mandatory specification compliance” (page 132None of the remaining exceptions have any impact regarding theinteroperability of Passport switches with other ATM Forum compliantequipment.

IMA on Passport fully complies with the optional requirements for ITC modof the ATM Forum Specification, with the exception of the specific sectiolisted in the table “Passport IMA optional specification compliance”(page 134). These exceptions may affect the interoperability of Passporswitches in ITC mode with other ATM Forum compliant equipment.

The following terminology applies to statements regarding compliance wspecification:

• Noted. This terminology applies where the specification providesclarification, non-specific information, or details that do not relatedirectly to Passport IMA.

• Fully complies with. This terminology applies where Passport IMAfunctionality fully complies with the text for this section.


132 Appendix Passport IMA compliance to specification

t

t

• Compliant with these exceptions. This terminology applies wherePassport IMA does not completely comply with the text. Additional texexplains specific exceptions.

• Not supported. This terminology applies where Passport IMA does nosupport the functionality described in the text.

Table 8Passport IMA mandatory specification compliance

Section Applicable requirement Compliance

Section R-54 The IMA transmitter shall perform acheck that an ATM Layer cell isavailable and accept that cell whenthe Tx IMA data cell clock (IDCC) ticksand only when the Tx IDCC ticks.

Compliant with these exceptions:

Passport does not implement the TxIDCC clock exactly as specified.There is no impact regardinginteroperability with specification-compliant equipment.

Section R-55 The transmit IMA shall derive the TxIMA data cell rate (IDCR) from theselected TRL according to (EQ. 1).


Passport does not implement the TxIDCR exactly as specified. There is noimpact regarding interoperability withspecification-compliant equipment.

Section R-61 The CDV attributed to the presence ofICP cells shall be removed by abehavior equivalent to providing asmall smoothing buffer into whichcells are placed after reordering andafter removing ICP cells (includingSICP cells), but not Filler cells.


Passport does not implement CDVsmoothing at the IMA layer. There isno impact regarding interoperabilitywith specification-compliantequipment.

Section R-62 If the TRL is in the Working state, theRx IDCR made available to the ATMlayer of the receiver shall be derivedas specified in equation (EQ. 1) usingthe incoming link indicated by the FEIMA transmitter as the TRL in the“Transmit Timing Information” field inthe ICP cell.


Passport does not implement the RxIDCR exactly as specified. There is noimpact regarding interoperability withspecification-compliant equipment.

(Sheet 1 of 2)

241-5701-730 5.1S1

Appendix Passport IMA compliance to specification 133

Section R-63 Zero or one cell only shall be madeavailable to the ATM layer at an IMAdata cell clock tick. The behavior ofthe IMA receiver shall be equivalent tofollowing: when the IMA data cellclock at the receiver ticks, one cellshall be removed from the smoothingbuffer.


Passport does not implement the RxIDCC clock exactly as specified.There is no impact regardinginteroperability with specification-compliant equipment.

Section R-97 The default value of Alpha (a) shall be2.


Passport implements Alpha = 1, whichis within the optional range specified.There is no impact regardinginteroperability with specification-compliant equipment.

Section R-133 In the case of the LODS failure alarm,the IMA shall support 2.5 0.5secondsas a default persisting checking timeto enter, and 10±0.5 seconds as adefault persisting clearing time to exit.


Passport implements a hysteresismethod to ensure that the LODSalarm does not toggle when thedifferential delay is near the maximumpermitted level. There is no impactregarding interoperability withspecification-compliant equipment.

Note 1: IMA on Passport fully complies with all mandatory requirements in the ATM Forum IMASpecification with the exception of the specific sections listed in this table.

Note 2: For a definition of the terms and acronyms used in the “Applicable requirement” columnof this table, see ATM Forum AF-PHY-0086.000, Inverse Multiplexing for ATM (IMA) Specification,Version 1.0.

Table 8 (continued)Passport IMA mandatory specification compliance


(Sheet 2 of 2)


134 Appendix Passport IMA compliance to specification

Table 9Passport IMA optional specification compliance


Section O-5 The transmit IMA may also supportthe ITC mode.


Passport’s implementation of ITCmode is not exactly as specified. See“Independent transmit clock (ITC)mode” (page 54) for details.

Section CR-4

Section CR-6

Note: For a definition of the terms and acronyms used in the “Applicable requirement” column ofthis table, see ATM Forum AF-PHY-0086.000, Inverse Multiplexing for ATM (IMA) Specification,Version 1.0.

241-5701-730 5.1S1

Passport 7400, 15000, 20000

Inverse Multiplexing for ATM Guide

Release 5.1

Copyright © 2003 Nortel Networks.All Rights Reserved.

NORTEL, NORTEL NETWORKS, the globemark design, the NORTELNETWORKS corporate logo, PASSPORT, and DPN are trademarks ofNortel Networks.VT100 is a trademark of Digital Equipment Corporation.

Publication: 241-5701-730Document status: StandardDocument version: 5.1S1Document date: March 2003Printed in Canada

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