H3C Technologies H3C SR8800 - Manual (Page 66)

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As the figure shows, in layered networks, MPLS TE is usually deployed only in the core layer, and MPLS
networks in the distribution layer usually use LDP as the label distribution signaling. To set up an LDP LSP
tunnel across the core layer, you need to establish a local LDP session between each pair of neighboring
LSRs in the core layer.
To simplify the configuration, when setting up an LDP LSP across the core layer, you can use the MPLS TE
tunnel that is already established in the core layer. As shown in Figure 23 , when using the MPLS TE tunnel
to establish the LDP LSP, you do not need to establish local LDP sessions between neighboring LSRs in the
core layer. All you have to do is to establish a remote session between the headend and tailend of the
MPLS TE tunnel. Then, label bindings can be exchanged and an LDP LSP can be established between the
MPLS TE tunnel headend and tailend. The LDP LSP is carried on the MPLS TE tunnel. In this way, a
hierarchical LSP is formed.
Figure 23 Configure an LDP LSP over an MPLS TE LSP
NOTE:
By default, LDP does not advertise any prefix-based label mapping message through a remote session. To
enable LDP to advertise prefix-based labels through a remote session, you need to configure the
prefix-label advertise command. For more information about the prefix-label advertise command, see
MPLS Command Reference.
Protocols and standards
• RFC 2702, Requirements for Traffic Engineering Over MPLS
• RFC 3212, Constraint-Based LSP Setup using LDP
• RFC 2205, Resource ReSerVation Protocol
• RFC 3209, RSVP-TE: Extensions to RSVP for LSP Tunnels
• RFC 2961, RSVP Refresh Overhead Reduction Extensions
• RFC 3564, Requirements for Support of Differentiated Service-aware MPLS Traffic Engineering
• ITU-T Recommendation Y.1720, Protection switching for MPLS networks
MPLS TE configuration task list
Complete the following tasks to configure MPLS TE: