© 1999, Cisco Systems, Inc. 6-1 QoS Chapter 6. © 1999, Cisco Systems, Inc. CMPLS 1.0—6-2...

© 1999, Cisco Systems, Inc. 6-1

QoSQoS

Chapter 6Chapter 6

© 1999, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—6-2

ObjectivesObjectives

Upon completion of this chapter, you will be able to perform the following tasks:• Discuss Quality of Service Policies

• Discuss the Service Class Templates


TopicsTopics

• IP QoS Concepts

• IP+ATM QOS implementation: 8650

• MPLS Command Line Interface

© 1999, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—6-4© 1999, Cisco Systems, Inc. www.cisco.com 6-4

IP QoS ConceptsIP QoS Concepts


Network Architecture

ConventionalRouter

Label EdgeRouters

ATM-LSR

Label SwitchingRouter (LSR)

Note: End to end service is IP; therefore, IP quality of service is what MPLS must support


Three Components of QOS Concepts

Three Components of QOS Concepts

• Packet Classification Policy

• Transmit Queue Scheduling Policy

• Transmit Queue Drop Policy


MPLS COS Differentiated Services

‘Differentiated Services’ approach:

• Classification: Set IP precedence at edge

• Scheduling: WFQ by class

• Transmit Drop: WRED by class

• Result: Provision for statistical delivery of high precedence traffic


Switching

rx queue tx queue

Tail Drop FIFO

tx hwrx hw

No QoS:No QoS:

•No Packet Classification Policy

•Scheduling Policy: Transmit Queue FIFO

•Transmit Queue Tail Drop Policy


Classification: Committed Access Rate (CAR)

Classification: Committed Access Rate (CAR)

• Used by router to classify received packets

• A flexible precedence setting mechanism

—Set precedence based on TCP and IP headers and conformance to a token bucket

—Uses Access-list logic to match packets

—Primary function: identify packets within profile and mark them at appropriate precedence value


Drop Policy: Weighted Random Early Detection

Manages queues that develop in routers during congestion

• Discards so that TCP windows are decreased, slowing ingress rate from application

• Provides RED benefits (shorter queues, improved fairness)

• Drops most from heaviest users, and from lower Precedence

P(drop)

Qavg


Scheduling Policy: Weighted Fair Queuing (WFQ)

Scheduling Policy: Weighted Fair Queuing (WFQ)

WFQ schedules transmission of packets during congestion

• Allocates link bandwidth to class by weight

• Unused bandwidth is available for other classes

• Provides bounded delay


MPLS Class of ServiceMPLS Class of Service

On non-ATM LSRs, it’s simple:

• Copy IP precedence to MPLS COS field

• Use MPLS COS as input to WRED

Net result is end-to-end QOS indistinguishable from non-MPLS network.

LERs connected to ATM and ATM-LSRs are the hard part.


COS on ATM-LSRsCOS on ATM-LSRs

Two challenges:

• No WRED in switches

• No COS field in cell header

Three modes:

• ATM Forum PVC

• Single ‘VC’ (LSP)

• Multi-’VC’ (LSP)


ATM Forum PVC mode

Usually used in non-MPLS enabled ATM core

Looks like a packet interface to MPLS CoS

BW and other parameters configured on the PVC

Requires significant amount of configuration

PVC


Multi-VC mode

MPLS ATM core provides MPLS CoS at each link by establishing parallel LVCs (up to 4)

Classification at MPLS ATM edge based on IP precedence

Scheduling Policy can assign weight to each class on per-link basis

Drop policy can use switch pre-existing discard thresholds mechanisms on switches

MPLS ‘LVCs’


Multi-VC mode example

• Queuing on all links is per-class WFQ

• E.g. Premium gets 80% of link, Standard gets 20%– Effect is to make premium see unloaded network

• Unused b/w available to other classes

• No per-router-pair configuration required


MPLS ‘VC’

Single ABR ‘VC’ modeSingle ABR ‘VC’ mode

• ABR control algorithms are enabled on LSRs

• ATM-LSRs push back on edge LSRs to eliminate congestion in ATM-LSR cloud

• non-ATM-LSRs respond to ABR feedback, manage per-VC queues using WRED, WFQ

• Drop decisions made where MPLS COS is visible - outside the ATM-LSR cloud.


Single VC ModeSingle VC Mode

ABR parameters• MCR is effectively zero (to avoid loss/blocking)

• Division of bandwidth among competing VCs may be uniform or configured


Single VC Mode Example

A

B

Chicago

New York

Nowheresville

Tinytown

• Fair sharing of link A-B is not always desirable

• Configure relative bandwidth on router-pair basis, e.g. Tinytown-Nowheresville = 1; Chicago-New York = 100

• Relative BW carried in TDP, used by ABR algorithms


IP+ATM QOS implementation:

8650 QBIN and SCT

IP+ATM QOS implementation:

8650 QBIN and SCT


COS in BPX SwitchesCOS in BPX Switches

Classification is at MPLS-ATM edge:

• Up to 4 LVC’s created per dest. prefix, based on TOS

• Scheduling Policy on BXMs based on weights given to each TOS

• Drop Policy based on cell discard features of QBINs


Scheduling Policy: 8650 QBINs

Scheduling Policy: 8650 QBINs

16 COS QBINs per interface

AutoRoute created VCs are placed into QBIN based on service type

CBR in QBIN 1, VBR in QBIN 2, etc.

MPLS uses QBINs 10-14


16 separate queues

CBR

UBR

ABR

ATM Queues

IP Queues

Class 1

Class 2

Class 3

IP Awareness in an IP+ATM Switch

IP Awareness in an IP+ATM Switch

ATM Partition:Bandwidth allocatedby VC

MPLS Partition:• Bandwidth allocated

by class• Separate labels per

class


Step 1:Define buffering

Step 2:Define bandwidth

50%

35%

15%

Gold

Silver

Bronze

Guaranteed: latency, deliveryGuaranteed: latency, delivery

Guaranteed: deliveryGuaranteed: delivery

Best effortBest effort

Class-Based WFQ: QoS Guarantees and Bandwidth Efficiency

Class-Based WFQ: QoS Guarantees and Bandwidth Efficiency

Weights guarantee minimum bandwidthBuffering controls latencyUnused capacity is shared amongst the other classes• proportional to their weights

Each queue can be separately configured for QoS (e.g. ABR)Benefits:• maximize transport of paying traffic• no loss of service class guarantees• no wasted bandwidth as with PVCs


Maximizing Bandwidth Utilization

Class-based WFQ: feature in Cisco IP+ATM switches

Each class is given guaranteed minimum bandwidth

If additional bandwidth is available each class can access a prioritized share

Used to manage available bandwidth between MPLS and ATM as well as individual IP and ATM service classes

For MPLS, applies to either ABR or Multi-TVC models

Unused BW

Sub-class 1Minimum BW = n

Time

Sub-class 2Minimum BW = 2n

Sub-class 3Minimum BW = n

Bandwidth

2n

n

n


BPX Drop PolicyBPX Drop Policy

Each QBIN has CLP low and high thresholds that define when cells should be discarded

Thresholds can be set on each QBIN


Service Class Template (SCT)

Provide a means of inferring extended parameters, which are generally platform-specific, from the set of standard ATM protocol parameters passed in VSI connection set-up primitives.

Provide support for different classes of service, I.E. MPLS COS 0, MPLS COS 1, etc.


SCT Definition

Service Templates have pre-defined, non-changeable values which are suited to typical interface uses

A set of Service Templates are stored on each switch, and are downloaded to the interface service modules as needed

In 9.2.1, 3 templates are supported: template 1 is for MPLS, 2 for UNI-ATMF, and 3 for NNI-ATMF


SCT Definition (cont.)

Service Templates contain two classes of data:

• One class consists of parameters necessary to establish a connection (i.e. per-VC)

• The second class of data items includes those necessary to configure the associated Class-of-Service Buffers that provide QoS support LSC Configuration


SCT VC Parameters

VC Descriptor Parameters MPLS Default ValuesMCR (%) MPLS 0-7: N/A TagAbr: 0Discard Selection EPDCDVT (msec) 250,000VSVD OffSCR (%) MPLS 0-7: N/A TagAbr: 0MBS (cells) MPLS 0-7: N/A TagAbr: 0Policing DisableICR (%) MPLS 0-7: N/A TagAbr:0ADTF (msec) MPLS 0-7: N/A TagAbr:500TRM (msec) MPLS 0-7: N/A TagAbr: 0VC Qdepth (cells) 61,440CLP Hi (%) 100CLP Lo/ EPD (%) 40EFCI (%) TagAbr: 20RIF (n where n is 1/(2^n)) TagAbr: 16RDF (n where n is 1/(2^n)) TagAbr: 16NRM (power of 2) TagAbr: 32FRTT (usec) TagAbr: 0TBE (cells) TagAbr: 16,777,215CAC Treatment LCNScaling Class MPLS 0-7: Scaled 1st TagAbr: Scaled 2nd


SCT QBIN Parameters

CoS Descriptor Parameters MPLS Default ValuesMax Threshold (usec) 95CLP High Threshold (%) 100CLP Low/EPD Threshold (%) 95EFCI (%) MPLS 0-7: 100 TagAbr: 6Discard Selection EPDVC Shaping On if BXM supports VC Shaping

CoS Number MPLS Class of Service10 MPLS 0, 411 MPLS 1, 512 MPLS 2, 613 MPLS 3, 714 TagAbr


QoS ConfigurationQoS Configuration


•A sample network

•A checklist of BPX and IOS configuration commands

•The configuration for the sample network, with command explanations and supporting dsp and show commands

ConfigurationConfiguration


Sample NetworkSample Network

bpx3bpx2

bpx1

2.1

4.1 4.1

2.1

2.2 2.1

mgx2

mgx1

mgx3

2.6

2.6 2.3

rtr2 rtr3

rtr1


Classification: Multi-VC mode (3 Steps)


1. Create COS map to correlate IP precedence to MPLS COS

2. Enable multi-vc mode on subinterfaces at MPLS-ATM edge

tag-switching atm multi-vc




3. Customize COS map, if desired

• Create COS map to define precedence-to-MPLS COS correlation

• Create ACL to match packets

• Create prefix map to connect COS map and ACL


Review: Existing RPM2 Configuration

Review: Existing RPM2 Configuration

Hostname rpm1ip cefrpmrscprtn par 100 100 0 299 0 3840 3840!addcon vpc switch 9/1.4 11 rslot 0 1 10!Interface loopback 0 ip address 10.2.2.2 255.255.255.255!Interface switch 9/1! Next sub is the sub connected to the LSCInterface switch 9/1.4 tag-switching ip unnumbered loopback 0 atm pvc 111 11 0 aal5snap tag-switching atm vp-tunnel 11 tag-switching ip!router eigrp 1 network 10.0.0.0


Classification: Multi-VC Mode (3 Steps)—Step 1

router#sho tag cos-map 1cos-map 1 class tag-VC 3 control

2 premium

1 standard

0 available

router#sho tag cos-map 1cos-map 1 class tag-VC 3 control

2 premium

1 standard

0 available

! Some commands from config review slide omitted to allow more space...Hostname rpm1ip cef!rpmrscprtn par 100 100 0 299 0 3840 3840!tag-switching cos-map 1!addcon vpc switch 9/1.4 11 rslot 0 1 10!Interface loopback 0 ip address 10.2.2.2 255.255.255.255!Interface switch 9/1! Next sub is the sub connected to the LSCInterface switch 9/1.4 tag-switching ip unnumbered loopback 0 atm pvc 111 11 0 aal5snap tag-switching atm vp-tunnel 11 tag-switching ip!router eigrp 1 network 10.0.0.0



! Some commands from config review slide omitted to allow more space...Hostname rpm1ip cef!rpmrscprtn par 100 100 0 299 0 3840 3840!tag-switching cos-map 1!addcon vpc switch 9/1.4 11 rslot 0 1 10!Interface loopback 0 ip address 10.2.2.2 255.255.255.255!Interface switch 9/1! Next sub is the sub connected to the LSCInterface switch 9/1.4 tag-switching ip unnumbered loopback 0 atm pvc 111 11 0 aal5snap tag-switching atm vp-tunnel 11 tag-switching ip tag-switching atm multi-vc!router eigrp 1 network 10.0.0.0



! Some commands from config review slide omitted to allow more space...! tag-switching cos-map 1 class 3 premium class 2 available class 1 available class 0 available!addcon vpc switch 9/1.4 11 rslot 0 1 10!Interface loopback 0 ip address 10.2.2.2 255.255.255.255!Interface switch 9/1! Next sub is the sub connected to the LSCInterface switch 9/1.4 tag-switching ip unnumbered loopback 0 atm pvc 111 11 0 aal5snap tag-switching atm vp-tunnel 11 tag-switching ip tag-switching atm multi-vc!router eigrp 1 network 10.0.0.0

router#show tag cos-map 1cos-map 1 class tag-VC 3 premium 2 available 1 available 0 available

router#show tag cos-map 1cos-map 1 class tag-VC 3 premium 2 available 1 available 0 available


Classification: Multi-VC mode (3 Steps)—Step 3 (cont.)

Assign cos-map to IP prefix using IP access list (multiple prefix-maps may be assigned):

router#sho ip access-list 1Standard IP access list 1 permit 10.0.0.0, wildcard bits 0.255.255.255

router#sho tag cos-map 2cos-map 2 class tag-VC 3 control 2 premium 1 available 0 available

router(config)#tag-switching prefix-map 1 access-list 1 cos-map 2


Scheduling: BPX (3 Steps)—Steps 1 and 2

Scheduling: BPX (3 Steps)—Steps 1 and 2

1. Confirm and/or assign SCT 1 to each trunk on BPX

cnfvsiif

2. On LSC, Assign % weights to each COS on each xtagatm extended port

tag-switching atm cos


3. On BPX, change QBIN discard threshold to affect latency

cnfqbin

Scheduling: BPX (3 Steps)—Step 3Scheduling: BPX (3 Steps)—Step 3


Interface 1/0

Sample Network Trunk Numbers

Sample Network Trunk Numbers

2.1

4.1 4.1

2.1

2.2 2.1

LSC1

bpx1

Trunk 2.8

bpx2

LSC2

bpx3

LSC3

Trunk 2.6RPM

PXM

mgx1

RPM

PXM

mgx3

Trunk 2.3RPM

PXM

mgx3

Trunk 2.6

Interface 1/0

Trunk 2.8

Interface 2/0

Trunk 2.8


! On LSC2:ip cef!interface atm 1/0 tag-control-protocol vsi id 1!interface loopback 0 ip address 10.1.1.2 255.255.255.255

interface XTagATM21 ip unnumbered Loopback0 extended-port ATM1/0 bpx 2.1 tag-switching ip!interface XTagATM41 ip unnumbered Loopback0 extended-port ATM1/0 bpx 4.1 tag-switching ip!router eigrp 1 network 10.0.0.0

Review: LSC ConfigurationReview: LSC Configuration


Scheduling: BPX (3 Steps)—Step 1

wegb134 TN StrataCom BPX 8620 9.2.01 June 29 1999 18:05 GMT

Trunk: 4.1

Service Class Template ID: 2

Last Command: dspvsiif 4.1

Next Command:


Trunk: 4.1


Last Command: dspvsiif 4.1

Next Command:


Trunk: 4.1


This Command: cnfvsiif 4.1 1


Trunk: 4.1





! On LSC2:ip cef!interface atm 1/0 tag-control-protocol vsi id 1!interface loopback 0 ip address 10.1.1.2 255.255.255.255!interface XTagATM21 ip unnumbered Loopback0 extended-port ATM1/0 bpx 2.1 tag-switching ip tag-switching atm cos control 50 tag-switching atm cos premium 25 tag-switching atm cos standard 15 tag-switching atm cos available 10

interface XTagATM41 ip unnumbered Loopback0 extended-port ATM1/0 bpx 1.5 tag-switching ip tag-switching atm cos control 50 tag-switching atm cos premium 25 tag-switching atm cos standard 15 tag-switching atm cos available 10

interface XTagATM261 ip unnumbered Loopback0 extended-port ATM1/0 bpx 2.6.1 tag-switching ip tag-switching atm cos control 50 tag-switching atm cos premium 25 tag-switching atm cos standard 15 tag-switching atm cos available 10




Qbin Database 4.1 on BXM qbin 10 (Configured by MPLS1 Template) (EPD Enabled on this qbin)

Qbin State: EnabledDiscard Threshold: 65536 cellsEPD Threshold: 95%High CLP Threshold: 100%EFCI Threshold: 100%

Last Command: dspqbin 4.1 10

Next Command:


Qbin Database 4.1 on BXM qbin 10 (Configured by MPLS1 Template) (EPD Enabled on this qbin)

Qbin State: EnabledDiscard Threshold: 65536 cellsEPD Threshold: 95%High CLP Threshold: 100%EFCI Threshold: 100%

Last Command: dspqbin 4.1 10

Next Command:


Example SummaryExample Summary

• Configuration for MGX2 and BPX2

• Default classification on MPLS-ATM edge (MGX2)

• No changes to BPX QBIN settings

• QBINs set to 50/30/15/5 for control, premium, standard, and available


Example: RPM2Example: RPM2

tag-switching cos-map 1 class 3 premium class 2 available class 1 available class 0 available!Interface switch 9/1! Next sub is the sub connected to the LSCInterface switch 9/1.4 tag-switching ip unnumbered loopback 0 atm pvc 111 11 0 aal5snap tag-switching atm vp-tunnel 11 tag-switching ip tag-switching atm multi-vc!router eigrp 1 network 10.0.0.0


Example: LSC2Example: LSC2

interface XTagATM21 ip unnumbered Loopback0 extended-port ATM1/0 bpx 2.1 tag-switching ip tag-switching atm cos control 50 tag-switching atm cos premium 30 tag-switching atm cos standard 15 tag-switching atm cos available 5!interface XTagATM41 ip unnumbered Loopback0 extended-port ATM1/0 bpx 4.1 tag-switching ip tag-switching atm cos control 50 tag-switching atm cos premium 30 tag-switching atm cos standard 15 tag-switching atm cos available 5

interface XTagATM261 ip unnumbered Loopback0 extended-port ATM1/0 bpx 2.6.1 tag-switching ip tag-switching atm cos control 50 tag-switching atm cos premium 30 tag-switching atm cos standard 15 tag-switching atm cos available 5!Router eigrp 1network 10.0.0.0


Summary Example: BPX2Summary Example: BPX2

bpx1 TN StrataCom BPX 8620 9.2.01 June 29 1999 18:07 GMT

Trunk: 1.2



bpx1 TN StrataCom BPX 8620 9.2.01 June 29 1999 18:07 GMT

Trunk: 1.2



cnfvsiif 2.1 1cnfvsiif 4.1 1cnfvsiif 2.6.1 1


SummarySummary

• Classification is done by using IP TOS

• Scheduling in core is based on BPX standard QBIN servicing

• Drop policy based on WRED if configured, and always by base BPX scheduling algorithms in IP+ATM

© 1999, Cisco Systems, Inc. 6-1 QoS Chapter 6. © 1999, Cisco Systems, Inc. CMPLS 1.0—6-2...

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Transcript of © 1999, Cisco Systems, Inc. 6-1 QoS Chapter 6. © 1999, Cisco Systems, Inc. CMPLS 1.0—6-2...