3Com S7902E, Configuration Manual

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The performance objectives associated with TE can be either of the following:
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Traffic oriented. These are performance objectives that enhance Quality of Service (QoS) of traffic
streams, such as minimization of packet loss, minimization of delay, maximization of throughput
and enforcement of service level agreement (SLA).
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Resource oriented. These are performance objectives that optimize resources utilization.
Bandwidth is a crucial resource on networks. Efficiently managing it is one major task of TE.
1) TE solution
As existing interior gateway protocols (IGPs) are topology-driven and consider only network
connectivity, they fail to present some dynamic 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 scalable
network design. It also provides better traffic and resources control support for implementing a variety of
traffic engineering policies.
Despite all the benefits, overlay models are not suitable for implementing traffic engineering in
large-sized backbones because of their inadequacy in extensibility. In this sense, MPLS TE is a better
traffic engineering solution for its extensibility and ease of implementation.
MPLS TE
MPLS is better than IGPs in implementing traffic engineering for the following:
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MPLS supports explicit LSP routing.
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LSP routing is easy to manage and maintain compared with traditional packet-by-packet IP
forwarding.
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Constraint-based Routed Label Distribution Protocol (CR-LDP) is suitable for implementing a
variety of traffic engineering policies.
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MPLS TE uses less system resources compared with other traffic engineering implementations.
MPLS TE combines the MPLS technology and traffic engineering. It delivers these benefits:
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Reserve resources by establishing LSP tunnels to specific destinations. This allows traffic to
bypass congested nodes to achieve appropriate load distribution.
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When network resources are insufficient, MPLS TE allows bandwidth-hungry LSPs or critical user
traffic to occupy the bandwidth for lower priority LSP tunnels.
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In case an LSP tunnel fails or congestion occurs on a network node, MPLS TE can provide route
backup and Fast Reroute (FRR).
With MPLS TE, a network administrator can eliminate network congestion simply by creating some
LSPs and congestion bypass nodes. Special offline tools are also available for the traffic analysis
performed when the number of LSPs is large.
Basic Concepts of MPLS TE
LSP tunnel
On an LSP, the nodes make forwarding decision for labeled packets based on label. The traffic thus is
transparent to the transits nodes on the LSP. In this sense, an LSP can be regarded as a tunnel.
MPLS TE tunnel
Reroute and transmission over multiple paths may involve multiple LSP tunnels. A set of such LSP
tunnels is called a traffic engineered tunnel (TE tunnel).