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Unformatted text preview: Traffic Engineering With Traditional IP Routing Protocols Bernard Fortz Jennifer Rexford Mikkel Thorup Institut dAdministration et de Gestion Internet and Networking Systems Universite Catholique de Louvain AT&T Labs Research Louvain-la-Neuve, Belgium Florham Park, NJ 07932 firstname.lastname@example.org f jrex,mthorup g @research.att.com Abstract Traffic engineering involves adapting the routing of traffic to the network conditions, with the joint goals of good user performance and efficient use of network resources. In this paper, we describe an ap- proach to intradomain traffic engineering that works within the existing deployed base of Interior Gate- way Protocols (IGPs), such as Open Shortest Path First (OSPF) and Intermediate System-Intermediate System (IS-IS). We explain how to adapt the configuration of link weights, based on a network-wide view of the traffic and topology within a domain. In addition, we summarize the results of several stud- ies of techniques for optimizing OSPF/IS-IS weights to the prevailing traffic. The paper argues that traditional shortest-path routing protocols are surprisingly effective for engineering the flow of traffic in large IP networks. 1 Introduction In some sense, IP networks manage themselves. A host implementing the Transmission Control Protocol (TCP) adjusts its sending rate to the bandwidth available on the path to the destination, and routers react to changes in the network topology by computing new paths. This has made the Internet an extremely robust communication network, even in the face of rapid growth and occasional failures. However, these mechanisms do not ensure that the network runs efficiently . For example, a particular link may be congested despite the presence of under-utilized links in other parts of the network. Or, a voice-over-IP call may travel over a route with high propagation delay when a low-latency path is available. Improving user performance and making more efficient use of network resources requires adapting the routing of traffic to the prevailing demands. This task is referred to as traffic engineering . In this paper, we focus on engineering the flow of traffic within a single Autonomous System (AS), such as a company, university campus, or Internet Service Provider (ISP). 1.1 Intradomain Traffic Engineering Traffic engineering depends on having a set of performance objectives that guide the selection of paths, as well as effective mechanisms for the routers to select paths that satisfy these objectives. Most large IP 3 2 5 2 1 4 1 1 3 3 Figure 1: Shortest path routing within an Autonomous System based on OSPF/IS-IS link weights: each link has an integer weight. networks run Interior Gateway Protocols (IGPs) such as OSPF (Open Shortest Path First) or IS-IS (Interme- diate System-Intermediate System) that select paths based on static link weights. These weights are typically configured by the network operators. Routers use these protocols to exchange link weights and construct aconfigured by the network operators....
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This note was uploaded on 01/25/2011 for the course SCE 5441 taught by Professor Lung during the Spring '10 term at Carleton CA.
- Spring '10