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Configuring MPLS TE
Overview
Network congestion is one of the major problems that can degrade your network backbone
performance. It might occur when network resources are inadequate or when load distribution is
unbalanced. Traffic engineering (TE) is intended to avoid the latter situation where partial congestion
might occur because of improper resource allocation.
TE can make the best utilization of network resources and avoid non-even load distribution by
real-time monitoring traffic and traffic load on network elements to dynamically tune traffic
management attributes, routing parameters and resources constraints.
The performance objectives of TE can be classified as either traffic oriented or resource oriented:
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Traffic-oriented performance objectives enhance QoS for traffic, such as minimization of packet
loss, minimization of delay, maximization of throughput and enforcement of service level
agreement.
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Resource-oriented performance objectives optimize resources utilization. Bandwidth is a
crucial resource on networks. Efficiently managing it is a major task of TE.
To implement TE, you can use IGPs or MPLS.
Because 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 on top of 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 scalability. In this sense, MPLS TE is a better
traffic engineering solution for its scalability and ease of implementation.
MPLS is better than IGPs in implementing traffic engineering for the following reasons:
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MPLS supports explicit LSP routing.
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LSP routing is easy to manage and maintain compared to 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 the following benefits:
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Reserve resources by establishing LSP tunnels to specific destinations, allowing 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 of 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 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.