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QoS DESIGN FOR MPLS VPN SUBSCRIBERSATAGLANCE

QoS design for an enterprise subscribing to a MultiprotocolLabel Switching (MPLS) VPN requires a major paradigmshift from private-WAN QoS design.

This happens because with private-WAN design, the enterprise

principally controlled QoS. The WAN Aggregator (WAG)provisioned QoS for not only Campus-to-Branch traffic, butalso for Branch-to-Branch traffic (which was homed throughthe WAG).

However, due to the any-to-any/full-mesh nature of MPLSVPNs, Branch-to-Branch traffic is no longer homed throughthe WAG. While Branch-to-MPLS VPN QoS is controlledby the enterprise (on their Customer-EdgeCErouters),MPLS VPN-to-Branch QoS is controlled by the serviceprovider (on their Provider EdgePErouters).

Therefore, to guarantee end-to-end QoS, enterprises mustco-manage QoS with their MPLS VPN service providers;their policies must be both consistent and complementary.

MPLS VPN service providers offer classes of service toenterprise subscribers.

Admission criteria for these classes is the DSCP markingsof enterprise traffic. Thus, enterprises may have to remarkapplication traffic to gain admission into the required serviceprovider class.

Some best practices to consider whenassigning enterprise traffic to serviceprovider classes of service include:

Do not put Voice and Interactive-Video

into the Realtime class on slow-speed( 768 kbps) CE-to-PE links

Do not put Call-Signaling into theRealtime class on slow-speed CE-to-PElinks

Do not mix TCP applications with UDPapplications within a single serviceprovider class (whenever possible);UDP applications may dominate theclass when congested

Exampleenterprise subscriber DSCP

Remarking Diagram and CE EdgeBandwidth Allocation Diagram.

A general DiffServ principle is to mark or trust traffic asclose to the source as administratively and technically possible.However, certain traffic types might need to be re-markedbefore handoff to the service provider to gain admission tothe correct class. If such re-marking is required, it is recom-mended that the re-marking be performed at the CEs egressedge, not within the campus. This is because service-provider

service offerings likely will evolve or expand over time, andadjusting to such changes will be easier to manage if re-markingis performed only at CE egress edges.

Copyright 2005 Cisco Systems, Inc. All rights reserved. Cisco, Cisco IOS, Cisco

Systems, and the Cisco Systems logo are registered trademarks of Cisco Systems, Inc.

and/or its affiliates in the U.S. and certain other countries.

All other trademarks mentioned in this document or Web site are the property of their

respective owners. The use of the word partner does not imply a partnership relationship

between Cisco and any other company. (0502R) 204170.r_ETMG_AE_4.05

WAGBranch

Branch

WAN

Central CEBranch CE

Branch CE

MPLS

VPN

Service Provider PE Routers

Voice

15%

Bulk

5%

Scavenger

1%

Net Mgmt

2%

Bulk 5%

Best Effort25%

Realtime35%

Critical

20%

Video

15%

Mission-Critical

Data 12%

Call-

Signaling 5%

Transactional Data

5%

Interactive-

Video

15%

Best Effort

24%

Streaming-Video

13%

Routing 3%

Enterprise Applications

Service Providerervice ProviderClasses of Servicelasses of Service

Service ProviderClasses of Service

REALTIME

35%

AF21 CS3

AF31/CS3 CS5

CS4 AF21

AF41 CS5

EF

CS2

AF11

CS1 0

0

CS6

Network Management

Call Signaling

Streaming Video

Transactional Data

Interactive-Video

Voice

EnterpriseApplications

Bulk Data

Scavenger

Best Effort

Routing

Mission-Critical Data AF31

DSCP

CRITICAL20%

VIDEO

15%

Service ProviderClasses of Service

EF

CS5

CS6

AF31

CS3

AF21

CS2

BEST EFFORT25%

BULK 5%AF11/CS1