4 1 qos overview

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Section 4 Introduction to Quality of

Service

Module 1QoS Overview


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QoS Overview Section 4 Module 1 Page 2

7450 ESS Services Implementation Alcatel University

Alcatel Proprietary, all rights

reserved 2006, Alcatel

Alcatel Proprietary, all rights reserved 2006, AlcatelQoS

7450 ESS Services Implementation


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Module Objectives

Upon successful completion of this module, the student will understand:

What Quality of Service (QoS) means and why it is desirable

Layer 2 and Layer 3 QoS classifiers

QoS implementation on the 7450 ESS including: Traffic Classification

Buffer management

Scheduling

Policing and shaping

Basics of hierarchical QoS


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What is quality of service?

> QoS characteristics:

Uses a combination of hardware and software to provide

consistent delivery of traffic across a network Distinguishes between different types of traffic in order to

allocate resources

QoS gives differential treatment to different types of traffic

Helps to use existing bandwidth more efficiently

Provides a way to deliver Service Level Agreements (SLA)

QoS techniques optimize:

Bandwidth

Delay

Jitter

Packet loss

7450 ESS Quality of Service (QoS)

QoS is an integral part of the 7450 ESS. QoS techniques, applied to both incoming and

outgoing traffic, support multiple customers and multiple services per physical interface. The

7450 ESS has extensive and flexible capabilities for classifying, policing, shaping, and

marking traffic.

QoS techniques classify traffic into forwarding classes, also known as classes of service or

types of service. A forwarding class provides network elements with a method to weigh the

relative importance of one packet over another. Traffic assigned to forwarding classes isplaced into queues and the contents of the queues are output in a controlled manner using

schedulers. The packets forwarding classalong with the in-profile and out-of-profile

statedetermines how the packet is queued and handled as it passes through each 7450 ESS

router.


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Quality of Service on the 7450 ESS

> Service differentiation

Uses differentiated service model (Diff-Serv)

> Aggregation and forwarding classes Large number of individual micro-flows are aggregated into forwarding

classes (8)

Mapping of traffic to forwarding classes (FC) is based on multi-fieldclassification rules

> Resource allocation

IOM resources are allocated on a per-FC basis

Performance of FC flows is provided through shaping, queuing, scheduling,and aggregate bandwidth reservation

> Traffic policing and shaping

Available at service ingress and egress

Policing prevents excessive traffic from congesting the network and assuringthat classified traffic conforms to SLAs

Shaping improves bandwidth utilization minimizes packets loss atdownstream policing points


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QoS Traffic Flow Example

1. Orange and purple traffic enters Node 1 through separate service access points (SAP).

Each SAP classifies its traffic into one or more forwarding classes based on multi-

field classification rules.

Classified packets are placed into queues based on the SAP they entered on and their

forwarding class. Purple traffic is queued separately from orange traffic.

Classification rules and queue parameters are defined in SAP-ingress QoS policies.

2. The forwarding class and profile status (in/out) of the purple and orange traffic is

translated into tunnel header QoS markings (Exp, DSCP, or dot1q bits). Translation is

defined in anetwork QoS policy.

All traffic, purple and orange, belonging to the same FC is queued together at the

network egress of Node 1. The parameters for network queues, which are different

from SAP-ingress queues, are defined by anetwork-queue policy. Queued packets

are serviced by virtual output queue (VoQ) schedulers and sent towards the

appropriate network port.

3. Purple and orange traffic arrives on the same network interface. The traffic is

classified into forwarding classes based on tunnel header markings. The tunnel

header to forwarding class translation is defined in anetwork QoS policy.

All network ingress traffic on an MDA uses a common buffer pool to create the

forwarding class queues. Purple and orange traffic belonging to the same FC is

placed into the same queue. Blue traffic, arriving on a SAP, is queued separately

from the purple and orange traffic.

The queued packets are serviced by a VoQ scheduler and sent towards the switching

fabric.

4. Because purple packets are coming from a network ingress on Node 2, they are

remarked only if the remark flag in the associated network QoS policy is enabled.

The purple packets egress port is different from the orange and blue egress ports, so

they are queued independently according to their FCs.


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QoS Traffic Flow Example

SAP

SAP

SAP

SAP

SAP

SAP

Purple A

Purple B

Orange A

Orange B

Blue A

Blue B

1

1. Traffic is classified into one or more forwarding classes or subclasses and placed into queues. Classification and queue

characteristics are set by SAP-ingress policies.

2. Traffic FC and profile status are mapped to tunnel header QoS markings (EXP, DSCP, or dot1p bits) as defined in a

network QoS policy. All traffic belonging to the same FC is queued together; network queue parameters are defined in a

network-queue QoS policy.

3. Traffic is mapped to FCs based on tunnel header markings; tunnel header to FC mapping is defined in a network QoS

policy.

4. Tunnel headers are remarked only if the remark flag in the associated network QoS policy is enabled.

5. SAP-Egress QoS policies define queuing and packet marking based on the traffic FC.

2

Node 1 Node 2

Node 3

Node 4

3

4

5

ePipe Services

Purple Service

5. A SAP-egress QoS policy defines queuing and packet marking based on FCs. Packets arequeued according to their SAP and forwarding class.

The queued packets are serviced by an egress VoQ scheduler and sent towards an egress port

for delivery to customers.

Traffic arriving at the ingress of Node 3 is processed in the same manner as traffic arriving at

the network ingress of Node 2.


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VersionLength

TOS1 Byte

TotalLength

ID Offset TTL Protocol FCS SA DA Data

Layer 3IPv4

Layer 2 and Layer 3 QoS Classifiers

Preamble SFD DA SA TAG

4 Bytes PT DATA FCS

Layer 2802.1Q/p

IEEE 802.1p

802.1p is a specification for giving Layer 2 switches the ability to prioritize traffic. The prioritization

specification works at the media access control (MAC) framing layer of the OSI model.

IP Precedence

IP Precedence/ToS changes the IP Precedence bits in the Type of Service (ToS) field in the IP

header. Based upon that change, the associated traffic receives priority within the IP network. To

enable this service, all IP routers and switches in the network must be configured to handle traffic

with the IP Precedence bits set.

Differentiated Services Code Point (DSCP)

A modification of the TOS byte. Six bits of this byte are reallocated for use as the DSCP field, where

each DSCP specifies a particular per-hop behavior that is applied to a packet.


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Traffic Classification - Internal Forwarding Classes

BE

L2

AF

L1

H2

EF

H1

NC

FC

Designation

Best Effort

Low-2

Assured

Low-1

High-2

Expedited

High-1

Network

Control

FC Name

0

1

2

3

4

5

6

7

FC ID

Intended for best effort traffic.Best

Effort

Intended for assured traffic.

Intended for assured traffic. Also the default

priority for network management traffic.

Assured

Intended for delay/jitter sensitive traffic.

Intended for network control traffic ordelay/jitter sensitive traffic.

Intended for network control traffic.High

Priority

DefinitionDefault

Class

Type

The 7450 supports eight internal forwarding classes. The default definitions are shown in theabove slide. Users can create QoS policies to configure the ingress marking interpretation and

egress marking behaviour of the forwarding classes.

The forwarding classes are grouped into three class types:

High-Priority

High-priority forwarding classes are serviced before other forwarding classes. These classes are

intended to be used for network control traffic or for delay or jitter-sensitive services (e.g. real

time traffic).

Assured

Assured forwarding classes provide services with a committed rate and a peak rate much like

ATM VBR service categories or Frame Relay. If the core network has sufficient resources in-

profile traffic will reach the service destination. When the network is congested out-of-profile

traffic will be discarded before in-profile traffic.

Best-Effort

The best-effort forwarding classes have no delivery guarantees. All packets in this class are

treated, at best, like out-of-profile assured type forwarding class packets.


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Service Ingress

Service

IngressService

Egress

Network

Ingress

Network

Egress

Service

Access

Point

Service

Access

Point

IP/MPLS

Network

PE PE

SAP SAP

Network QoS Policies

Service QoS Policies

service ingress/egress point can be delimited by a physical port or encapsulation (VLAN, Frame Relay)

SAP-ingress QoS policy:

defines traffic queues (type, en-queuing and de-queuing parameters, mode, etc.)

assigns forwarding classes to queues

maps traffic to a forwarding class or sub-class based on user-defined match criteria and assigns in or out-of-profile status to the packets

is applied to SAPs for IES, ePipe and VPLS services

support for 8 unicast queues, one for each internal forwarding class

VPLS service supports 3 additional queues per forwarding class (broadcast, multicast, and unknown)

support for up to 32 queues per SAP

shared queuing supported for IES and VPLS services

support for hierarchical scheduling (H-QoS)

At service ingress to the 7450 ESS traffic can be classified into one of eight internal forwardingclasses (FC) and mapped to a queue. Traffic classification is achieved with ingress QoS policy

match criteria.

IP and MAC match criteria for service ingress traffic:

IP or application information (L3 L7)

Source IP address/prefix Destination IP address/prefix Source port/range Destination port/range

Protocol type (TCP, UDP, etc.) DSCP value IP fragment

Source MAC, Destination MAC or Layer 2 criteria

IEEE 802.1p value/mask Source MAC address/mask Destination MAC address/mask EtherType type

IEEE 801.2 LLC SSAP value/mask

IEEE 802.2 LLC DSAP value/mask IEEE 802.3 LLC SNAP PID value IEEE 802.3 LLC SNAP OUI zero or non-zero value


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Service Ingress QoS Policy Configuration


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Network Egress

Service

IngressService

Egress

Network

Ingress

Network

Egress

Service

Access

Point

Service

Access

Point

IP/MPLS

Network

PE PE

SAP SAP



each network egress port supports a queue for each of the 8 internal forwarding classes; queues are created

automatically when a port is configured as a network port

queue parameters are defined in a network-queue QoS policy; on network egress the policy is applied to

an entire port


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Network Egress QoS Policy Configuration

config>qos#

net workpolicy-iddescri pt i on description-stringscope {excl usi ve| t empl ate}egress

remarking

fc {be|l2|af|l1|h2|ef|h1|nc}

dscp-in-profile dscp-name

dscp-out-profile dscp-name

lsp-exp-in-profilempls-exp-value

lsp-exp-out-profilempls-exp-value

i ngr essdef aul t - acti on f c {be| l 2| af | l 1| h2| ef | h1| nc} [ prof i l e{i n| out }]dscpdscp-name f c {be| l 2| af | l 1| h2| ef | h1| nc} [ prof i l e{i n| out }]l er - use- dscp

l sp- exp lsp-exp-value f cfc-name [ prof i l e {i n| out }]


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Network Ingress

Service

IngressService

Egress

Network

Ingress

Network

Egress

Service

Access

Point

Service

Access

Point

IP/MPLS

Network

PE PE

SAP SAP



each forwarding class is supported by an ingress queue per MDA

network ingress queues are created automatically when a port is placed in the network mode queue parameters are defined in a network-queue QoS policy; on ingress the policy is applied at the

MDA level to all network ingress ports on the MDA

network-ingress QoS policy defines the mapping of DSCP and EXP bits to one of the 7450 internal

forwarding classes


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Network Ingress QoS Policy Configuration

config>qos#

net workpolicy-iddescri pt i on description-stringscope {excl usi ve| t empl ate}

egr essr emarki ngf c {be| l 2| af | l 1| h2| ef | h1| nc}dscp- i n- prof i l e dscp-namedscp- out - prof i l e dscp-namel sp- exp- i n- prof i l e mpls-exp-valuel sp- exp- out - pr of i l e mpls-exp-value

ingress

default-action fc {be|l2|af|l1|h2|ef|h1|nc} [profile{in|out}]

dscpdscp-name fc {be|l2|af|l1|h2|ef|h1|nc} [profile{in|out}]

ler-use-dscp

lsp-exp lsp-exp-value fcfc-name [profile {in|out}]


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Service Egress

Service

IngressService

Egress

Network

Ingress

Network

Egress

Service

Access

Point

Service

Access

Point

IP/MPLS

Network

PE PE

SAP SAP



SAP-egress QoS policy define:

forwarding class to output queue mapping

in/out-of-profile marking to high/low priority mapping egress queue en-queue and de-queue parameters

support for hierarchical scheduling (H-QoS)


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Service Egress QoS Policy Configuration

conf i g>qossap- egr esspolicy-id

descri pt i on description-stringscope {excl usi ve| t empl at e}f cfc-name

dot 1p dot1p-valuequeue queue-id [ pr i or i t y {l ow| hi gh}]

conf i g>qos# sap- egr ess 100 creat econf i g>qos>sap- egr ess$ descr i pt i on "SAP egr ess pol i cy 100"conf i g>qos>sap- egr ess# queue 2 cr eateconf i g>qos>sap- egr ess>queue$ exi tconf i g>qos>sap- egr ess# f c ef creat e

conf i g>qos>sap- egress>f c# queue 2conf i g>qos>sap- egr ess>f c# exi tconf i g>qos>sap- egr ess# queue 3 expedi t e cr eateconf i g>qos>sap- egr ess>queue$ adapt at i on- r ul e pi r cl osest ci r cl osestconf i g>qos>sap- egr ess>queue# par ent t est 1conf i g>qos>sap- egress>queue# exi tconf i g>qos>sap- egr ess# exi t


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Network-Queue QoS Policy

> Network Queue Policies:

define the network forwarding class queue characteristics

are applied at egress to core network ports and channels are applied at ingress to MDAs

> Network queue policies can be configured to use as many queues as

needed. This means that the number of queues can vary. Not all policies will

use eight queues like the default network queue policy.


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Network-Queue QoS Policy Configuration

conf i g>qosnet work- queuepolicy-name

descri pt i on description-string

f cfc-namemul t i cast - queue queue-idqueue queue-id

queue queue-id [ mul t i poi nt ] [ queue-type]cbspercenthi gh- pr i o- onl ypercentmbspercentratepercentage [ ci rpercentage]

Exampl e:

conf i g>qos# net work- queueNQ1 createconf i g>qos>network- queue# descr i pt i on "Network Queue Policyconf i g>qos>network- queue# f c beconf i g>qos>net workqueue>f c# exi tconf i g>qos>networ k- queue# queue 1conf i g>qos>net workqueue# exi t


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Network-Queue QoS Policy Application

Applying a policy to all network ingress ports on an MDA:

conf i g>car dmdamda-slotnet work

i ngr essqueue- pol i cy name

Applying a policy to a network egress port:

conf i g>por t #ethernet

net workqueue- pol i cy name


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Traffic Service Queues

> Queues created as needed

> Multiple FC per Queue if desired

> Defines packet to FC classification rules

> Per virtual port queuing

Queues are created by applying QoS Service Policies:

All packets received from subscribers must be classified for proper handling within theaggregated service core network. The aggregated packets within the core network are not

treated on a per service basis, but on a forwarding class and profile basis.

7450 ESS routers support eight (8) forwarding classes (FC). Each forwarding class is

important only in relation to the other forwarding classes. A forwarding class provides

network elements with a method to weigh the relative importance of one packet over another

in a different forwarding class.

Queues are created for a specific forwarding class to determine the manner in which the queue

output is scheduled into the switch fabric and the type of parameters the queue accepts. Theforwarding class of packets, along with their in-profile or out-of-profile state, determines how

packets are queued and handled (the per hop behavior (PHB)) at each hop along the path to a

destination egress point.

The forwarding classes are grouped into three categories:

High-priority

Assured

Best effort


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Queue Buffer Management

Each 7450 ESS forwarding complex has 256 Mb of buffer space available for ingress traffic

and 256 Mb for egress traffic queues. Buffer space management ensures that services are

segregated from each other and that no one service will use a disproportionate amount of

system resources.

Reserved Buffers

Reserved buffer space is a percentage of the total buffer space allocated to a queue. You can

configure the amount of reserved buffer space allocated to each queue, the default being fifty

percent of the total buffer space of the queue. The amount of reserved buffer space for a queue

is known as the committed burst size (CBS) of the queue.

Shared Buffers

Shared buffer space is the buffer space that is not reserved for use by specific queues.

Shared Buffers = Total Buffer Pool Reserved Buffers

Any queue can use non-allocated shared buffer space if its reserved buffer space is full and it

has not exceeded its maximum burst size (MBS).

Shared buffer utilization is managed by WRED.

Committed Burst Size (CBS)

The CBS parameter specifies the amount of buffer space reserved for use by a given ingress o

egress queue. Once the reserved buffer space for a queue has been used, the queue contends

with other queues for additional buffer resources up to the Maximum Burst Size (MBS) of the

queue. The CBS for a given queue can be configured or the system can assign a default size.

Maximum Burst Size (MBS)

The Maximum Burst Size parameter specifies the maximum size to which a queue can grow.

This parameter ensures that customers that are exceeding the PIR of a queue will not consume

all the available buffer resources. The MBS for a given queue can be configured or will be

assigned a default value by the system.

Service ingress and egress QoS policies define CBS and MBS for each queue separately, and

the network QoS policy defines CBS and MBS for each network queue.


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Buffer Management Queue Attributes

Queue

Configured as a% of total

buffer space

0xMax

High-Priority-OnlyWater Mark

Highpriorityonly

Shared Buffers

CBS

Reserved buffers are a subset of the buffer pool reservedfor queue allocation.Each queue is allocated a number of reserved buffers.Reserving buffers per queue prevents a queue from beingstarved of buffer resources by other queues.

The Committed Burst Size (CBS) parameter defines theamount of reserved buffer space for a queue.

Shared buffers are buffers within a buffer poolthat are not reserved for specific queues.

The number of shared buffers within a bufferpool is the difference between the total number

of buffers and the reserved buffers.

Any queue within the buffer pool may use anon-allocated shared buffer if its reservedbuffers are full and it has not exceeded itsMaximum Burst Size (MBS).

Sharing buffers within a buffer pool allows the7450 ESS to absorb bursts using the largestpossible pool of buffers while maintainingforwarding class and service separation.

Reservedbuffers

MBS

A portion of the shared buffer space can bereserved for traffic marked as high-priority-only.

After buffer space up to the the high-priority-onlywater mark is used, only high-priority-only trafficwill be allowed into the queue.

Reserved High-Priority-Only Buffers

Reserved High-Priority-Only buffers are defined on service ingress queues and allow buffers to

be reserved for traffic classified as high-priority traffic as defined by the service ingress QoS

policy. When a queue depth reaches a specified level, only traffic marked as high-priority-only

can be placed into the queue.


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Buffer Management - WRED

Shared Buffers Reserved

buffers

LowEnqueuing

Traffic

SLOPE

HighEnqueuing

Traffic

SLOPE

Average Shared Buffer Utilization

Discard

Probability

0

1

Slope Knee

Slope Start

WRED and Shared Buffer Management

Weighted Random Early Detection (WRED) monitors the shared buffer space utilization over a period

of time. WRED uses the shared buffer utilization rather than any individual queue depth to get a better

picture of the average resource utilization of the shared buffer space.

A large amount of buffer space is important to absorb the traffic while the TCP session senders adjust

their round-trip time calculations and throttle their output. The instantaneous value of the weighted

average is used to determine the discard probability of a given packet at the time it arrives at a queue.

The discard probability is a fractional number ranging from zero to one and describes the probability of

discarding a packet subject to a WRED slope. Two points relative to weighted average utilization anddiscard probability define each slope:

The weighted average utilization where discard probability starts to rise above zero

The weighted average utilization and discard probability point defining where discard probabilityrises straight to one.

Two configurable slopes are defined per buffer pool:

a high slope

a low slope

Traffic from expedited (premium) traffic queues is not subject to WRED. Only traffic from non-

expedited traffic queues (assured and best effort) will be affected by the WRED algorithm.


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Buffer Management - WRED Configuration

Average Shared Buffer Utilization

Discard

Probability

0

1

Max-avg

Start-avg

Max-prob

1 2

3

4

1 No Discard

2 Random Discard

3

4All Discard

Once a queue exceeds its reserved buffer allocation and starts using shared buffers, each service packetmapped to that queue is subject to the probability based drop function. The above slide depicts WRED

slope configurable parameters. Each slope is configured with thresholds describing points on the slope

that intersect the average utilization of the shared portion of the buffer pool (X-axis or horizontal plot

with utilization increasing from 0 to 100%) and the probability of discard (Y-axis or vertical plot with

probability rising from 0 to 1).

Configurable parameters are:

Start-avg

Sets the low priority or high priority WRED slope position for the shared buffer average utilization

value where the packet discard probability starts to increase above zero.

Max-avg

Sets the low priority or high priority WRED slope position for the shared buffer average utilization

value where the packet discard probability rises directly to one.

Max-prob

Sets the low priority or high priority WRED slope position for the maximum non-one packet discard

probability value before the packet discard probability rises directly to one.


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Queue Schedulers

All ingress and egress queues operate under the control of one or more schedulers. Several

queues may use the same scheduler.

Schedulers control the data transfer between the following queues and destinations:

Service ingressswitch fabric destinations.

Service egressaccess egress ports.

Network ingressswitch fabric destinations.

Network egressnetwork egress interfaces.

Queue Committed Information Rate (CIR)

The CIR of a queue performs two functions:

1. Profile marking - Service ingress queues mark packets in-profile or out-of-profilebased on the queue's CIR.

2. Scheduler queue priority metric - The scheduler serving a group of ingress oregress queues prioritizes individual queues based on their current CIR and PIR

states. Queues operating below their CIR are always served before queues

operating at or above their CIR.

Queue Peak Information Rate (PIR)

PIR defines the maximum rate at which packets are allowed to exit a queue.

PIR does not specify the maximum rate at which packets may enter a queue; this is governed

by the queue's ability to absorb bursts and is defined by the maximum burst size (MBS).

The PIR is provisioned on ingress and egress service queues, within SAP-ingress and SAP-

egress QoS policies respectively. The PIR of service queues is defined in Kbps (Kilobits/sec).

The PIR for network queues are defined within network-queueQoS policies. The PIR fornetwork queues is defined as a percentage of the network interface bandwidth.

Note:normally it is good practice to make PIR=CIR for high-priority FC queues.


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Scheduling - Queue CIR & PIR

PIR = Peak Information Rate

PIR defines the maximum rate atwhich packets are scheduled out ofa queue.

CIR = Committed Information Rate

CIR defines the threshold up towhich packets scheduled out of thequeue are marked In-profile andconform to CIR. Once the scheduledrate of packets out of the queuepasses the CIR threshold, packetsare marked Out-of-Profile.

ServiceQueue


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Scheduling - Single Tier Hardware Schedulers

Packets are scheduled out of aqueue according to thefollowing criteria:

1. Expedited


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Scheduling - Hierarchical Virtual Schedulers

Strict / WeightedRate Limiting

Scheduler


Scheduler


Scheduler


Scheduler

Strict / Weighted

Rate LimitingScheduler

Queue

Queue

Queue

Queue

Queue

Queue

3 levels supported

Allows lower priority

traffic to make use

of unused bandwidth

when higher priority

traffic is below CIR

Hierarchical Schedulers (H-QoS)

The 7450 ESS makes use of hierarchical virtual schedulers to implement hierarchical QoS (H-QoS).

H-QoS creates a hierarchy of schedulers configured in a series of parent-child relationships.

The levels of scheduler policies are then treated according to their assigned priority. This

design allows the 7450 ESS to implement very granular QoS policies consisting ofcombinations of strict priority queuing and weighted fair queuing for bandwidth management.


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Scheduling - Hierarchical QoS Applications

> Multi-ApplicationSLA

Each application getsreserved bandwidth butlower priorityapplications can burstto use all availablebandwidth.

Sum of CIRs=5Mb/s

Overall PIR=12Mb/s

CIR=0

PIR=max

PIR=max

PIR=3 Mb/s

PIR=2 Mb/s

CIR=2 Mb/s

CIR=3 Mb/s

CIR=0

OverallPIR

12 Mb/s

Voice

Video

Business

Best Effort

> Multi-Site SLA Customer with two

offices connecting tosame VPN, sharingone SLA. Each officehas its own CIR, butcan burst to use anyavailable bandwidth.

VPLSVPLS

12Mb/s

> Multi-ServiceSLA

Customer sharingone SLA betweenInternet accessand VPN services.Internet traffic canburst if VPN isbelow CIR.

VPLSVPLS

12Mb/s


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Overriding QoS policies

> Enhance the capabilities of QoS templates

> Allows an existing QoS policy to be instantiated and thenmodified to suit the new situation

> Allows you to

Re-use a QoS policy (i.e. use it as a template)

Override that template

> Can be used with QoS policies and schedulers

ScenarioAn operator has 3 types of services: HSI, Video and Voice. Each subscriber can buy service

packages with different bandwidth for each service.

HSI: 2, 4, 6 Mbps

Video: 6, 12 Mbps

Voice: 384, 768, 1536 Kbps

With traditional QoS policies, 47 types of policies (variations) are required, or each subscriber

must be configured individually. Overriding allows the use of only 7 templates: HIS only,Video only, Voice only, HSI+Video, HSI+Voice, Video+Voice, HSI+Video+Voice. Eachindividual subscriber can then be assigned bandwidth at the SAP level, by applying and then

overriding one of the 7 templates.


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Overriding QoS policies example

QoS policy

conf i gur e qos sap- i ngr ess 101 createdescr i pt i on Thi s i s t he base queue def i ni t i on for HSI and Vi deodef aul t - f c bedef aul t - pr i or i ty l owqueue 1 cr eate

parent hsiexi tqueue 2 cr eate

parent vi deoexi tf c be c reate

queue 1exi tf c ef cr eat e

queue 2exi tpr ec 4 f c ef pr ec 0 f c be

exi t

Applying and overriding the policy

conf servi ce epi pe 101 cust omer 1create

sap 1/ 2/ 15 creat ei ngr ess qos 101qos- override

queue 1r at e 1024exi tqueue 2

r ate 768exi t

exi texi t

exi t

In this example, sap-ingress policy 101 was created as a template policy.

The policy was then applied to sap 1/2/15 with the override keyword. The changes to thetemplate policy are the rates of queues 1 and 2 (to match for this customer agreed to pay for).


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Questions

1. How many internal forwarding classes does the 7450 ESS support?

a. 2

b. 8c. 16

d. 4

2. What is the default method of scheduling queues in the 7450 ESS?

a. Single tierb. Hierarchical

3. Which of the following groups, A or B describes the default scheduling priority of the7450 ESS:

a. High scheduler queues operating within CIRLow scheduler queues operating within CIR

High scheduler queues operating within PIR

Low scheduler queues operating within PIR

b. High scheduler queues operating above CIR but within PIRLow scheduler queues operating within CIR

High scheduler queues operating above CIR but within PIRLow scheduler queues operating within PIR


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Answers

1. How many internal forwarding classes does the 7450 ESS support?

a. 2

b. 8 c. 16

d. 4

2. What is the default method of scheduling queues in the 7450 ESS?

a. Single tier b. Hierarchical

3. Which of the following groups, A or B describes the default scheduling priority ofthe 7450:

a. High scheduler queues operating within CIR Low scheduler queues operating within CIR

High scheduler queues operating within PIR

Low scheduler queues operating within PIR

b. High scheduler queues operating above CIR but within PIRLow scheduler queues operating within CIR

High scheduler queues operating above CIR but within PIRLow scheduler queues operating within PIR

4 1 qos overview

Documents

qos overview section

qos overview5282018

qos characteristics

ess service differentiation

excessive traffic

mapping of traffic

andmarking traffic

the7450 ess