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Operation Manual – MPLS TE
H3C S9500 Series Routing Switches
Chapter 1 MPLS TE Configuration
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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.
1.1.2 Basic Concepts of MPLS TE
I. 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.
II. 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).
1.1.3 MPLS TE Implementation
MPLS TE mainly accomplishes two functions:
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Static constraint-based routed LSP (CR-LSP) processing to create and remove
static CR-LSPs. The bandwidth of LSPs must be configured manually.
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Dynamic CR-LSP processing to handle three types of CR-LSPs: basic CR-LSPs,
backup CR-LSPs and fast rerouted CR-LSPs.
Static CR-LSP processing is simple, while dynamic CR-LSP processing involves four
phrases: advertising TE attributes, calculating paths, establishing paths, and
forwarding packets.
I. Advertising TE attributes
MPLS TE must be aware of dynamic TE attributes of each link on the network. This is
achieved by extending link state-based IGPs such as OSPF and IS-IS.
OSPF and IS-IS extensions add to link states such TE attributes as link bandwidth,
color, among which maximum reservable link bandwidth and non-reserved bandwidth
with a particular priority are most important.
Each node collects the TE attributes of all links on all routers within the local area or at
the same level to build up a TE database (TEDB).