CCC and TCC Graceful Restart

CCC and TCC graceful restart allows Layer 2 connections between customer edge (CE) routers to restart gracefully. These Layer 2 connections are configured with the remote-interface-switch or lsp-switch statements. Because these CCC and TCC connections have an implicit dependency on RSVP LSPs, graceful restart for CCC and TCC uses the RSVP graceful restart capabilities.

RSVP graceful restart must be enabled on the PE routers and P routers to enable graceful restart for CCC and TCC. Also, because RSVP is used as the signaling protocol for signaling label information, the neighboring router must use helper mode to assist with the Resource Reservation Protocol (RSVP) restart procedures.

Figure 26 illustrates how graceful restart might work on a CCC connection between two CE routers.

Figure 26: Remote Interface Switch Connecting Two CE Routers Using CCC

PE Router A is the ingress for the transmit LSP from PE Router A to PE Router B and the egress for the receive LSP from PE Router B to PE Router A. With RSVP graceful restart enabled on all the PE and P routers, the following occurs when PE router A restarts:

• PE Router A preserves the forwarding state associated with the CCC routes (those from CCC to MPLS and from MPLS to CCC).
• Traffic flows without disruption from CE router to CE router.
• After the restart, PE Router A preserves the label for the LSP for which PE Router A is the egress (the receive LSP, for example). The transmit LSP from PE Router A to PE Router B can derive new label mappings, but should not cause any traffic disruption.

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