atm basic v1

8/11/2019 ATM Basic v1

1/59

1 Nokia Siemens Networks Presentation / Author / Date

For internal use

ATM Basics


2/59


For internal use

Synchronous Transfer Mode

Derived from TDM technology

Divides the physical bandwidth into logicaltimeslots

Circuit switched networks (voice and leased lines)


3/59


For internal use

Asynchronous Transfer Mode

A compromise for voice, data, and video

QoS defined/negotiated when the initial connection ismade

Asynchronous on layer 2 of the OSI reference model

Compromise of STM and PTM

Voice Video Data

ATM cells

48-octet

Payload

ATM 53-octet cells are

switched in hardware


4/59


For internal use

New world packet networks

Layer 1 to layer 3 in the OSI reference model

Layer 1: PDH or (Plesiochronous Digital Hierarch)

SDH/SONET (Synchronous Digital Hierarchy)(Synchronous Optical Network, SONET)

DWDM optical(Dense Wave Division Multiplexing)

Layer 2:

ATM

Frame Relay

PPP (Point to Point Protocol)

EthernetLayer 3:

IP (Internet Protocol)


5/595 Nokia Siemens Networks Presentation / Author / Date

For internal use

What is ATM & Why

ATM = Asynchronous Transfer Mode

Fast packet switching and multiplexing technology (cell-based )

ATM provides efficient supportfor transmission ofvoice, data, and video

ATM provides QoS guaranteeand reliability

ATM utilises statistical multiplexing, so

less bandwidth can be reserved

transmission cost saving are considerable



For internal use

For a group of bursty connections,less bandwidth can be reserved thanif bandwidth reservation would bebased on the peak rate of theconnections

Most of the traffic sources sendbursty traffic and with a highprobability all the sources do notsimultaneously transmit at their peakrate

One of the proposed advantages ofATM is that statistical multiplexinggain can be utilized

Statistical multiplexing gain

Statistical multiplexing Deterministic multiplexing

Required

bandwidthPeak cell rate oftraffic type 1

Peak cell rate oftraffic type 2

Peak cell rate oftraffic type 3

Statistical Multiplexing Gain



For internal use

ATM interfaces in 3G network

UNI User Network InterfaceNNI Network Node Interface

PSTNMGW MSCBSUE

A BIu-CSIubUu

UNI NNI

IP networkGGSN

Iu-PS

NNI

RNC

SGSN

RNCBS

BS

Iur

NNI

UNI

UNI

ATM is employed

Gn Gi


8/59


For internal use

ATM Essential for 3G

ATM Cell

ATM Virtual Path (VP) and Virtual Channel(VC)

ATM Adaptation Layer (AAL) (AAL2 andAAL5)

ATM Layer Service Class (CBR,UBR)

ATM Cross Connect

Inverse Multiplexing for ATM (IMA)

ATM over PDH and SDHFractional E1 and Circuit Emulation Service(CES)


9/59


For internal use

ATM cell

Header contains routing and error control information

Payload carries the actual user information, either voice, data orvideo

Header5 bytes

Payload48 bytes

53 bytes


10/59


For internal use

GFC Generic Flow ControlVPI Virtual Path IdentifierVCI Virtual Channel Identifier

PT Payload TypeCLP Cell Loss PriorityHEC Header Error Control

User Network Interface (UNI) Network Node Interface (NNI)

VCI

GFC VPI

VPI

VCI

VCI PT CLP

HEC

123457 68

VCI

VPI

VPI

VCI

VCI PT CLP

HEC

123457 68

Payload Payload

Header(5 bytes)

Payload(48 bytes)

Provides local functions,such as identifying multiplestations that share a singleATM interface

The 1st bit - indicates whether thecell contains user data or controldataThe 2nd bit - indicates congestion

Indicates two levels ofpriority for ATM cells,CLP=1 should bediscarded in preference tocells with the CLP=0


11/59


For internal use

ATM cell header

GFC provides local functions.VPI indicates the virtual path over which the cell should berouted.

VCI identifies a virtual channel over which the cell is totravel.

PT discriminates between a cell carrying managementinformation or one, which is carrying user information.

CLP indicates two levels of priority for ATM cells.

HEC checks for an error and corrects the contents of theheader by using a CRC algorithm.


12/59


For internal use

VCI / VPI FieldFunctions

Switching Identifiers Routing

Multiplexing

The concept of virtual channels and virtual paths

Identifiers

VCI identifies a Virtual Channel

Connection VPI identifies a Virtual Path Connection

Transmission Path could be PDH orSDH


13/59


For internal use

Adaptation

Layer

ATM

Layer

Physical

Layer

Conversion to

ATM Data

Types, 48-Byte

Length

Forward Cell

Through

Network

Add 5-Byte

Header

Convert To

Correct

Electrical Or

Optical

Format

Voice

Cell

Data

Cell

Video

Cell

Services

A

ATM Cell Creation


14/59


For internal use

Hierarchy

Virtual channel connection

AAL2 connection

Virtual path connection

Transmission path

AAL2 link

Virtual channel link

Virtual path link

Physical link

VPCTP

VCCTPVCLTP

VPLTP VPLTP VPLTP VPLTPVPCTP

VCLTPVCLTPVCLTPVCCTP

Transmission path

VP

VCs

CIDs


15/59


For internal use

ATM in VP and VC

48 bytes

5 bytes

HEADER PAYLOAD

ATM cell (53 bytes)

Transmission

path

Virtual

Path

(VP)

Virtual

Channel

(VC)

ATM Cell

ATM Layer

HEADER

PAYLOAD


16/59


For internal use

ATM Adaptation Layer

Typical

Use

FixedConnection

Video&

Audio

FrameRelay

IPServices

AALAAL1 AAL2 AAL3/4 AAL5

Connection OrientedConnection oriented or

connectionless

Synchronised Not Synchronised

Constant VariableBit Rate

Source & Dest.

Connection

ATM Layer

Physical Layer

A B C D

ATM Service Classes

PBX

Video Voice DataAA

L


17/59


For internal use

ATM layer functions

Convergence Sublayer (CS)

PayloadPayload HeaderHeader

48 bytes5 bytes

User data

AAL

Segmentation and ReassemblySublayer (SAR)

ATM Layer

Transmission Convergence(TC)

48 bytes

Physical Medium Dependent(PMD)

SDH

O/H

PayloadHeader

Scramble frame and adaptsthe signals to the optical orelectrical transmissionmedium

STM-1 Frame

PhysicalLayer


18/59


For internal use

ATM Adaptation Layer 2 (AAL2)

One AAL2 cell flow consists of variable length "mini-cells" that are concatenated as acontinuous stream into the 48-byte payload areas of ATM-cells

The "mini-cells" are officially called CPS-packets (Common Part Sublayer), & aredivided into packet header (PH) and packet payload (PP) parts

Mini-cells have a "mini-header" (CPS-PH) to identify the channel and length of themini-cell

Mini-cell payload size can be anything from 1 to 45 bytes

Channels can be multiplexed in any order desired, mini-cells can cross ATM-cellboundaries, cells can be padded

All AAL2 ATM-cells begin with a start field which indicates the offset to 1st completemini-cell within the ATM-cell

AAL2 ATM-cell flow

Cell payloadCell header

Channel 3 flow

Start field CPS-PH CPS-PP

Channel 1 flow

Channel 2 flow

Offset to next CPS-PDU

Zero padding

Crossing cellboundary

AAL2 (ATM Adaptation Layer 2)


19/59


For internal use


String of AAL2 Packet Data Units String of AAL2 Packet Data Units

1 2 3 4 5 6

AAL2header

ATM CELLHEADER

ATM CELLHEADER

HEADER= 5 BYTES

PAYLOAD= 48 BYTES

1 2 3 4 4 5 6

ATM cell

OFFSET FIELD, 1 byte (indicates where the next AAL2 PDU starts)

AAL2 PACKET, fixed header, variable length payload (max. 48 bytes)

ATM CELL, 5-byte header + 48-byte payload

PADDING


20/59


For internal use

ATM Adaptation Layer 5 (AAL5)

AAL5 ATM Adaptation layer is designed to carry fast streams of longer packets over

ATM as simply as possibleAAL5 doesn't provide any multiplexing itself, it is assumed that the packets carried

identify themselves to higher protocol layers (like TCP/IP)

AAL5 is also known as SEAL (Simple Efficient Adaptation Layer)

Packets are simply segmented into 48-byte fragments of ATM-cell payloads, the lastcell is padded and terminated with AAL5 trailer of 8 bytes

AAL5 trailer indicates packet length & has 32-bit CRC

Packets can be up to 64 Kbytes and are aligned to cell boundaries

The last cell of a packet is indicated by setting the PT[0] bit in cell header

Packet #1

cell #1 cell #2

Cell payload

Cell header

Packet #2

cell #3 cell #4

Zero padding

AAL5 packettrailer

UU

CPI

CRC-32

length

Crossing cellboundary

AAL5 packettrailer

Zero padding



21/59


For internal use


PADDING FIELD, variable length to fill the 48-byte ATM cell

AAL5 PACKET, fixed trailer, variable length payload (max. 64 Kbytes)

ATM CELL, 5-byte header + 48-byte payload

AAL5 Packet Data Unit

USER DATA - Variable length 1 - 65 535 bytes

PAYLOAD= N x 48 BYTES

AAL5trailer

ATM cell 1 ATM cell 2... ..ATM cell n

AAL5 Packet Data Unit

USER DATA - Variable length 1 - 65 535 bytes

ATM L S i Cl


22/59


For internal use

ATM Layer Service Classes

CBR (Constant Bit Rate)

VBR (Variable Bit Rate)

ABR (Available Bit Rate)

UBR (Unspecified Bit Rate)

Time

Bandwidth

Time

Bandwidth


23/59


For internal use

ATM capacity of an E1 frame

Number of bytes with ATM payload is 30 in a frame

Frame repetition rate is 1/125 us.30 bytes/125 us = 240 000 bytes/s

One ATM cell has 53 bytes/cell .

The ATM traffic capacity in a 2 Mbps frame is

240000/53 = 4528 cps or

30 ts * 8 bit * 8000 = 1920000 bits/s = 1920 kbps

ATM over


24/59


For internal use

ATM cell mapping into PDH 2048 kbps

PDH frame structure for 2048 kbps is describedin ITU-T Recommendation G.704

ATM cell is mapped intobits 9 to 128 and bits 137 to 256

(i.e. time slots 1 to 15 and time slots 17 to 31)Time slots 0 and 16 are not used for ATM cell

Bit 1 Bit 8

Bit 9 Bit

Bit 121 Bit 12

Bit 129 Bit 13

Bit 137 Bit 14

Bit 249 Bit 25

TS 1

TS 0

TS 30

TS 31

ATM overPDH


25/59

ATM over SDH


26/59


For internal use

ATM over SDH

VC-4

OVERHEAD

STM-1 (155,52 Mbps) can fit 44.15 cells per frame-> 353 207 cells per second.

VP1

VP2

VP3

.

.

.

ATM Capacity in STM 1 VC 4 Frame


27/59


For internal use

ATM Capacity in STM-1 VC-4 Frame

Payload of the STM-1 frame can accommodate 1 Virtual ContainerLevel-4 (VC-4)

Total ATM capacity in a SDH frame:

Payload per virtual container: 260x9 = 2340 bytes

Frame repetition rate is 125 us.

2340 bytes/125 us = 18 720 000 bytes/s One ATM cell has 53 bytes/cell .

The ATM traffic capacity in a SDH frame is: 18 720 000 bytes/s/53 bytes = 353 207 cps

In case STM-0 is used (3x VC3 within STM-1) 114113 cps areavailable per logical interface

ATM Cross Connection


28/59


For internal use

ATM Cross Connection

From the origin to the termination of a Virtual Channel Trail there can be multipleintermediate Nodes where ATM Cross Connections might occur

Aggregation close to the BTS saves in transmission costs However in many networks there is only one switch between the BTS and RNC

Traffic is collected from different origins to same destination

Statistical multiplexing gain can be achieved

RNC

STM1

BTS

E1

BTS

E1

BTS

E1

BTS

E1BTS

E1

VP and VC Cross Connections


29/59


For internal use

VP and VC Cross Connections

ATM cross connections can be performed at VP or VC level VP level switching is preferred in some cases as it makes management and

configurations easier The physical link is terminated at any intermediate Node

Virtual Paths can be cross connected to any Physical Interface

Virtual Channels can be cross connected to any Virtual Path

Which layer is terminated depends on the Cross Connection Level

Cross Connections are carried out according to a Cross Connection Table

VC Cross

Connection

VP Cross

Connection

VCI 21VCI 22

VCI 21

VCI 22

VPI 1

VPI 4

VPI 1VPI2

VPI3

VCI 21

VCI 22

VCI 24

VCI 23

ATM Cross Connect


30/59


For internal use

VPI 1

VPI 2

VPI 3

VPI 4

VPI 5

VPI 6

VCI 1VCI 2

VCI 1

VCI 2

VCI 3

VCI 4

VCI 3

VCI 4

VCI 5

VCI 6

VCI 5

VCI 6

Virtual Path Switching

VPI 1

VPI 2

VCI 1

VCI 2

VCI 1VCI 2

VPI 1

VPI 4

VCI 4

VCI 5

VCI 6

VCI 3

VPI 5Port 1

Port 2

Port 3

Virtual Channel Switching

VPI and VCI values


31/59


For internal use

VPI and VCI values

VPI re-use

One VPI value can be used once in the same ATM interface. Can be re-used in another ATMinterface

VCI re-use

One VCI value can be used only once within the same VP, but can be re-used in another VPVP Cross Connection:

VPIs will be re-assigned on the other interface, but could have previous value if available.

VCIs remain the sameVC Cross Connection

The VP will be terminated The VCI will be re-assigned on the VP but could have previous value if available.

ATMUNI

ATMNNI

ATMNNI

ATMUNI

VC-levelXCON

VP-levelXCON

VC-levelXCON

VPI/VCI is modified atconnection points

VPI/VCI is assigned atendpoints

VPI = 37VCI = 41

VPI = 7VCI = 65

VPI = 12VCI = 41

VPI = 57VCI = 65

ATM cross-connect (AXC)


32/59


For internal use

ATM cross-connect (AXC)

VC2 / VP2

VC1 / VP1

RNC

ATMswitch

VC1 / VP1

BTS 1

AXC

VC3 / VP3VC3, VC4 / VP4

VC3, VC4, VC5, VC6 / VP7VC5 / VP5

VC6 / VP6

VC1/VP1 THROUGH-CONNECTED IN AXC2

VC/VP CROSS-

CONNECTION TABLEVC3/VP4 VC3/VP 7VC4/VP4 VC4/VP 7VC5/VP5 VC5/VP 7VC6/VP6 VC6/VP 7

AXC / ATM switch

BTS 2

AXC

BTS 3

AXC

BTS 4

AXC

BTS 5

AXC

BTS 6

AXC

StandaloneAXC

ATM resource management Iub


33/59


For internal use

ATM resource management Iub

P

hyTTP

ATMlo

gicalinterface

VP

Ltp

VPLtp

VC

Ltp

ATMlo

gicalinterface

VP

Ltp

VPLtp,

O&M traffic (UBR)

Signalling and user traffic (CBR)

VC

Ltp

VCLtp

VCLtp

VCL

tp

VCLtp

VCLtp

VCLtp

VCLtp

VCLtp

Common NBAP link (C-NBAP)

Dedicated NBAP link (D-NBAP)

Dedicated NBAP link (D-NBAP)

AAL2 signalling link (AAL2SL)

AAL2 signalling link (AAL2SL)

AAL2 user plane link (AAL2UD)



VCLtp

VPLtp


VCLtp

VCLtp

VCLtp

VCLtp

VCLtp

VCLtp

VCLtp

VCLtp

VCLtp

RNC

WAM

WAM

P

hyTTP

O&M / Usage IPOAM



34/59


For internal use

Problem ?:More bandwidth than 2 Mbit/s is needed, but

only T1/E1 services are offered by the carrier

PBXPBX

ATM

E1 based


PBX PBX

ATM

E1 based

Multiple T1/E1s are bundled for more bandwidth

Solution IMA

Concept of IMA


35/59


For internal use

Tx direction:cells distributed across links in round robin seque

Rx direction:cells recombined into single ATM stream

Physical Link #0

Single ATM Cell Streamfrom ATM Layer

IMA Virtual Link

IMA Group

PHY

PHY

PHYPhysical Link #1

Physical Link #2

IMA Group

PHY

PHY

PHY

Original ATM CellStream to ATM Layer

p

Low bit rate transmission lines can be combined into a group thatseen as a single virtual link by ATMIMA sublayer is part of the physical layer.

It is located between the traditional Transmission Convergence sublayer andthe ATM layer.

Inverse multiplexing for ATM


36/59


For internal use

Inverse multiplexing for ATM

ATM Layer

Physical Medium Sublayer

TransmissionConvergenceSublayer (TC)Physical Layer TC

IMA

Iub IMA max 8 E1Iur IMA max 16 E1All E1 in IMA have to belong to same NIP or IFUOnly one ATM interface/ IMA group

NIP1 can have up to 16 ATM Interfaces

IMA frame - ICP cell, Filler cell


37/59


For internal use

ATMATM ICPFiller

Cell0

Cell1

Cell2

Cell3

Cell4

Cell5

Cell6

Cell7

CellM-1

ATM ATM ATM ATMFiller

FillerFiller ICPATM ATM ATMATMATM ATM

An IMA Frame

M consecutive cells transmitted on each link within the IMA group M can be 32, 64, 128 or 256. NSN default: 128

The ICP (IMA Control protocol) cell is sent once per IMA frame on each link witha different offset between different links, to adjust for differential link delays ICP fields contain e.g. link ID, IMA ID, IMA Frame Sequence Number, ICP Cell Offset

If there are no ATM layer cells to be sent the transmit IMA sends Filler cells.

Note: IMA is not saving bandwidth but enables to utilize the available bandwidthmore efficiently and protects from link and interface failure!

IMA failure case


38/59


For internal use

Upon the failure of one or more links or interfaces of an IMA group, the IMAEngine is able to recover and reassign the distribution of ATM cells to the

remaining working PDH links within the IMA group. Only the capacity of this IMA group is reduced but the IMA group remains operational.

The recovery time of the IMA engine upon PDH link failure is 2 s, all existingcalls will be terminated.

Example:

IMA group with 4 E1 links An ATM interface with a VP of 17000 cps is assigned to that group

Note: IMA group with 4 E1s provides a capacity of 17961 cps

Minimum number of links is set to 2

In case 1 or 2 E1s drop out the IMA group continuous operating after restart with alimited bandwidth even if the logical interface cannot provide anymore the assigned

VP capacity

Transmission (2G/3G)


39/59


For internal use


TDM Channel based allocation (16kbit/s, 64kbit/s etc)

ATM

Cell based allocation (1 ATM Cell =53 bytes, 424 bits (vs. 256bits in E1 (32 TS)))

1 ATM cell requires more than one E1 frame

Usable capacity for ATM in E1 is 1920kbit/s (30x64kbit/s) In case fractional E1 is used -> TS16 available



40/59


For internal use


234

567891011121314

1516171819202122232425262728293031

10 LINK MANAGEMENT

TCH 1TCH 5TCH 1TCH 5

TCH 1TCH 5TCH 1TCH 5TCH 1TCH 5TCH 1TCH 5







TRX#1

TRX#2

TRX#3TRX#4

TRX#5

TRX#6

Sector#1

Sector#2

Sector#3

ATMATM traffic768 kbit/s

TRXSIG 1 TRXSIG 2 TRXSIG 3 TRXSIG 4TRXSIG 5 TRXSIG 6 OMUSIG TRXSIG1-

6&OMUSIGAvailable for TDM traffic

Available for TDM traffic

Transmission (2G/3G; Fractional E1)


41/59


For internal use

Transmission (2G/3G; Fractional E1)

RNC

BSC

ET

Node B AXC

IFUA

ATMtraffic

TRS EQ

TRS IF NIU

E1

2G BTSTRUx

TDMtraffic

Fractional E1(TDM+ATM)

TDM X-connect

ATMSWITCH

ATM over E1


42/59


For internal use

Header Payload

0 1 2 16 1817 3115

TS0TS1-15

TS16TS17-31

. . . . ..

0 1 2 16 1817 3115

TS0TS1-15

TS16TS17-31

. . . . ..

E1 frameE1 frame

Fractional E1


43/59


For internal use

3G ATM Traffic Sharing GSM 2M Frame

MetroHub

GSM

BTS

WCDMA

BS RNC

BSC

TDM

Fractional E1

Fractional E1


44/59


For internal use

- INFractional E1 some timeslots are not used for ATM traffic(configurable by management), TS0 and TS16 are not allowed by default

- using only three timeslots provides a 192 kbit/s transmission path for ATM- long transmission delays for ATM traffic!

TS0 TS0

fractional E1termination point

fractional E1termination point

3 octets of the ATM cell 3 octets of the ATM cell

53 octets per ATM cell

Circuit Emulation Service (C


45/59


For internal use

GSM Traffic Over ATM

SAXC or

WCDMA

BTS-AXC

GSM

BTS

WCDMA

BS RNC

BSC

ATM

CES

Circuit Emulation Service (C

Circuit Emulation


46/59


For internal use

RNC

BSC

ET

E1 from 2G BTS

ATMSWITCH

Non fractional E1

AXCIFU A

NIU

2G BTSTRX

TRX

TRX

TRX

TRX

TRX

TRUA

D-busLIF1

WSP WSP

3G BTS AXC

...

WSP WSP...

IFU A

IFU EWAM

WAM

CESIWF

Flexbus connection

E1

VCC

VCC

VCC

VPC

AXU

CESIWF

VCC

VCC

VCC

VPC

IFU E

Unstructured Circuit Emulation Service


47/59


For internal use

- Transmitting CES interworking function takes the E1 si and segments that stream into ATM cells- ATM cells are transported via a CBR VCC to the receiving CES

interworking function- receiving CES interworking function recovers E1 signal from the A cell stream- Note: CES works bidirectional

CESInterworking

Function (IWF)

CESInterworking

Function (IWF)

TS0 TS0 TS0 TS0

G.703 frames

Structured Circuit Emulation Service


48/59


For internal use

- Transmitting CES interworking function takes only sometimeslots

from the E1 signal puts these into ATM cells

- ATM cells are transported via a CBR VCC with lower bandwidthcompared tounstructured CES to the receiving CES interworking function

- receiving CES interworking function recovers TS from the ATM cellstream- Note: CES works bidirectional

CESInterworking

Function (IWF)

CESInterworking

Function (IWF)

TS0 TS0 TS0 TS0

TS1-TS3

Protocol Stacks of User Plane for CS/PS services


49/59


For internal use

AAL2

PHY

ATM

PHY

ATM

AAL2

FP

PHY

AAL2

PHY

ATM

LinkLayer

PHY

AAL2

PHY

ATM

WCDMAL1

FP

WCDMAL1

E.g.,Vocoder

PHY

PSTN/N-ISDN

MGW

RNC

BTS

UE

Iu-CS UP

E.g.,

Vocoder

LinkLayer

A/m-lawPCM,UDI,etc.

A/m-lawPCM,UDI,etc.

MSC

RLC-U

MAC

RLC-U

MAC

UE BTS RNC MGW / MSC /SGSN GGSN

IP

AAL5

PHY

UDP

LLC/SNAP

GTP-U

ATMPHY

ATMAAL2

FP

PDCP

UDP

IP

LinkLayer

PHY

GTP

IP

AAL5

PHY

UDP

LLC/SNAP

GTP-U

ATM

UDP

IP

LinkLayer

PHY

GTP

AAL2

PHYATM

WCDMAL1

FPWCDMA

L1

PDCP

E.g.,IPv4, IPv6

PHY

E.g.,IPv4, IPv6

GGSN

3G-SGSNRNC

BTS

UE

RLC-UMAC

RLC-UMAC

Also forNRTservicesAAL2 isused onATM asTransportLayer

Iu-CS UP

Iub

IuUu

Quality of Service


50/59


For internal use

To guarantee the required QoS, there is a method defined to describe connectionsbehavior

Service category classifies connections as CBR,UBR or UBR+

Traffic parameters define mainly the bandwidthrequirements e.g. PCR / MCR

QoS parameters define finally the QoS of the

Connection such as delay, cell loss etc.

Service Classes

Traffic Parameters

QoS Parameters

QoS Class

The combination of the Traffic Class and

the set of Traffic and QoS parametersconstitute the Connection TrafficDescriptorof an ATM connection

ATM service categories - CBR


51/59


For internal use

CBRConstant Bit Rate

Used for constant (maximum) bandwidth

services For the connections that request a fixed

(static) bandwidth, that is continuouslyavailable during the connection lifetime

Is intended to support real-time applicationsrequiring tightly constrained delay variation

The applications are e.g. video, audio, circuitemulation, but use of CBR does not restrictedto those applications

PCR is guaranteed

Used for signaling traffic (CNBAP, DNBAPand AAL2SIG)

Used for user plane VCCs All user plane VCCs CBR in RNC until RAS06

Time

Bandwidth

ATM service categories - UBR


52/59


For internal use

UBRUnspecified Bit Rate

Is intended for non-real-time applications,

i.e., those not requiring tightly constraineddelay and delay variation.

Examples of applications are traditionalcomputer communication applications,such as file transfer and email

Service does not specify traffic relatedguarantees

Sources are expected to transmit non-continuous bursts of cells

PCR is not guaranteed and

Traditionally DCN and Iu-PS connectionshave been UBR

Time

Bandwidth

?

ATM service categoriesUBR+


53/59


For internal use

UBR+Unspecified Bit Rate + Is intended for non-real-time applications,

i.e., those not requiring tightly constraineddelay and delay variation.

Examples of applications are traditionalcomputer communication applications,such as file transfer and email

Specified with PCR and MDCR

MDCR is guaranteed and traffic can be

transmitted up to PCR (in RNC) Picture is indicating that even though the

MDCR is reserved for the traffic, the trafficcan reach up to the PCR, if there is freecapacity to be used e.g. in the VPC orBundle

Time

Bandwidth

PCR

MDCR

Note! UBR+ has also proprietaryUBRshare parameter that is used to

share excess capacity between different

UBR+ VCC in the line card.

Traffic and QoS Parameters


54/59


For internal use

Traffic parameters describe traffic in terms of: PCR - Peak Cell Rate

Maximum bandwidth in any situation MDCR - Minimum Desired Cell Rate

Parameter defines the guaranteed cell rate

QoS Parameter: CDVT - Cell Delay Variation Tolerance

This parameter is set according to network element requirements (details follow!) CLR - Cell Loss Ratio:

Describes the ratio of lost cells to transmitted cells

The CLR parameter is the value that the network agrees to offer as an objective overthe lifetime of the connection

If value will be exceeded an alarm will be raised or possibly further action will be

triggered depending on parameter settings Usual values between 10-3to 10-9

Traffic Management


55/59


For internal use

Traffic management is needed in order to comply to the QoS requirements

QoS is guaranteed as long as the connection is compliant with the Traffic

contract The traffic offered to the network can be variable and therefore end-to end

participation of network elements is required

Picture: Traffic management functions with in ATM node are distributed among differentelements

Policing

CAC

Interface

Control

module

Switch fabric

BufferingCongestion control

Queuing

Traffic priorities

Shaping

Buffering

Interface

IngressCells in

EgressCells in

Traffic Contract


56/59


For internal use

Definition of a Compliant Connection

QoS class

Traffic Descriptor

Cell Delay Tolerance

Cell Loss Ratio

Peak Cell Rate

Service Category

A

Traffic contract is negotiated during connection establishment

Its an agreement between a user and a network, where the network guarantees

a specific QoS if the user's cell flow conforms to a negotiated set of trafficparameters

A traffic contract can be also a written contract between an Operator and e.g. abackbone / Leased Line provider.

Traffic contract of includes:

Definition of a Compliant Connection


57/59


For internal use

QoS is guaranteed as long as the connection is compliant with the traffic contract

Committed to provide the agreed QoS to all cells conforming the traffic contract,

the network needs to police the traffic to detect non-conforming cells Network takes appropriate actions to prevent non-conforming cells from affecting

the QoS of the conforming cells of the other connections

The network could drop cells

Conformance test performed on the traffic stream, defined in the trafficdescription

CBR.1 for CBR (only available for CBR)

UBR.1 for UBR (default), cell will be discarded if non-conformant

UBR.2 for UBR, cell will be tagged (CLP bit set to 1) and forwarded

If conformance definition is UBR.1 then packets violating the traffic contract will bediscarded.

For UBR.2 non-compliant cells will be first tagged (CLP) and then discarded whenrecognized again as non-compliant.

CDVTCell Delay Variation Tolerance


58/59


For internal use

In this example we assume only 4 VCCs with a low capacity,mapped into an interface of a little higher capacity.

Imagine a SDH-interface with a 23 times higher capacity, wherehundreds of VCCs are mapped in.

Line rate 15kcps = 1 cell every 67s

125s white CV-CDVT = 500s

8000 cps = 400s = 500s = 333s

4000 cps

2000 cps

= 267s = 67s

1000 cps

blue CV-CDVT = 1000s

250 s

500 s

1000 s

XCON

CDVT - Cell Delay Variation Tolerance


59/59


For internal use

Time budget, how much earlier than expected ATM cells are allowed to arrive

Normally, ATM cells are expected every 1/PCR.

If an ATM cell arrives earlier than expected, the next ATM cell is expected laterthan 1/PCR in order to compensate.

Typical value of CDVT = 1/PCR.

Example:

Line rate = 5000 cell/s1 ATM cell takes 200 s

VCC PCR = 2000 cell/s1 redATM cell per 500s.

CDVT = 1/PCR = 1/2000 s = 500 s.

expected arrival time

actual on or after expected arrival time.

actual prior to expected arrival time,if > CDVT, discard cell.

Bits are received at time ...

400 01200 80016002000t [s]

= 0 s, OK = -100 s

OK

= -300 s, OK

= -600 sNOK

Tx Rx

atm basic v1

Documents