91Configuring MPLS TEThe S5500-28SC-HI and S5500-52SC-HI switches do not support MPLS TE.OverviewNetwork congestion is one of the major problems that can degrade your network backboneperformance. It may occur either when network resources are inadequate or when load distribution isunbalanced. Traffic engineering (TE) is intended to avoid the latter situation where partial congestionmay occur as the result of inefficient resource allocation.TE can make the best utilization of network resources and avoid non-even load distribution by real-timemonitoring traffic and traffic load on each network elements to dynamically tune traffic managementattributes, routing parameters and resources constraints.The performance objectives for TE can be classified as either traffic-oriented or resource-oriented.• Traffic–oriented performance objectives enhance Quality of Service (QoS) of traffic streams, suchas minimization of packet loss, minimization of delay, maximization of throughput and enforcementof service level agreement (SLA).• Resource–oriented performance objectives optimize resources utilization. Bandwidth is a crucialresource on networks. Efficiently managing it is a major task of TE.To implement TE, you can use interior gateway protocols (IGPs) or Multiprotocol Label Switching (MPLS).Because IGPs are topology-driven and consider only network connectivity, they fail to present somedynamic factors such as bandwidth and traffic characteristics.This IGP disadvantage can be repaired by using an overlay model, such as IP over ATM or IP over FR.An overlay model provides a virtual topology above the physical network topology for a more scalablenetwork design. It also provides better traffic and resources control support for implementing a variety oftraffic engineering policies.Despite all the benefits, overlay models are not suitable for implementing traffic engineering inlarge-sized backbones because of their inadequacy in extensibility. In this sense, MPLS TE is a bettertraffic engineering solution for its extensibility and ease of implementation.MPLS is better than IGPs in implementing traffic engineering for the following reasons:• MPLS supports explicit LSP routing.• LSP routing is easy to manage and maintain compared with traditional packet-by-packet IPforwarding.• MPLS TE uses less system resources compared with other traffic engineering implementations.MPLS TE combines the MPLS technology and traffic engineering. It delivers the following benefits:• Reserve resources by establishing LSP tunnels to specific destinations, allowing traffic to bypasscongested nodes to achieve appropriate load distribution.• When network resources are insufficient, MPLS TE allows bandwidth-hungry LSPs or critical usertraffic to occupy the bandwidth for lower priority LSP tunnels.• In case an LSP tunnel fails or congestion occurs on a network node, MPLS TE can provide routebackup and Fast Reroute (FRR).
