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DiffServ Traffic Engineering Tunnels Overview

This topic discusses how Differentiated Services Aware Traffic Engineering LSPs (DS-TE LSPs) are modeled in NorthStar Planner. In order to provide the most value to users, NorthStar Planner’s modeling of DS-TE LSPs are continually updated to reflect current vendor implementations and industry practices in this field. Therefore, it is possible that the descriptions of DS-TE LSPs may not reflect the traditional DS-TE LSP models (E-LSPs and L-LSPs) defined by IETF. For more information on traditional DS-TE LSP models, feel free to peruse IETF RFC 3270. In this document, the DS-TE LSP behavior discussed is that which is currently implemented by today’s hardware vendors. Currently, only Juniper Networks supports DS-TE LSPs.

Whereas standard traffic engineering works on an aggregate basis, DS-TE LSPs allow for traffic engineering at a per-class level with different bandwidth constraints for different traffic class types. This makes it possible to guarantee different levels of service and bandwidth to different classes across an MPLS network. Such advantages allow you to provide ATM circuit emulation over IP, Voice over IP, class based services, and guaranteed bandwidth services.

Before reading this chapter, you should have a good understanding of how standard LSPs are provisioned on a network, and you should be comfortable working with LSPs.

It should be noted that in this topic, the word “tunnel” is used in the context of traffic engineering (TE) tunnels. Also, the word “tunnel load” refers to the amount of IP traffic transported by the tunnel.

The following terms are used in this topic and related topics:

  • Bandwidth Model: The bandwidth model determines the values of the available bandwidth advertised by the interior gateway protocols (IGPs).

  • Differentiated Services: Also known as DiffServ, differentiated services make it possible to give different treatment to traffic based on the experimental (EXP) bits in the MPLS header.

  • DSCP: The Differentiated Services Code Point refers to six bits in the ToS (Type of Service) byte of a packet header that specify the particular PHB (Per Hop Behavior) to be applied to the packet.

  • DS-TE LSP: Differentiated-Services-aware Traffic Engineering LSP.

  • E-LSP: EXP-inferred LSP as defined in IETF RFC 3270.

  • L-LSP: Label-only-inferred LSP as defined in IETF RFC 3270.

  • Planned Bandwidth: The current bandwidth allotted to the tunnel.

  • QoS: Quality of Service is a broad collection of networking technologies with the goal of providing guarantees on the ability of a network to deliver predictable results beyond the best-effort delivery provided by default.