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MPLS Transport Profile Overview
RFC 5654, Requirements of an MPLS Transport Profile, describes the requirements for the MPLS Transport Profile (MPLS-TP) that extends capabilities for Operation, Administration, and Maintenance (OAM) when MPLS is used for transport services and transport network operations. These capabilities help in troubleshooting and maintenance of a pseudowire or label-switched path (LSP).
MPLS-TP mechanisms for OAM contain two main components:
- Generic Associated Channel Label (GAL)—A special label that enables an exception mechanism that informs the egress label-switching router (LSR) that a packet it receives on an LSP belongs to an associated control channel or the control plane.
- Generic Associated Channel Header (G-Ach)—A special header field that identifies the type of payload contained in the MPLS label-switched paths (LSPs). G-Ach has the same format as a pseudowire associated control channel header.
For more information about MPLS-TP, see RFC 5654, Requirements of an MPLS Transport Profile. For specific information about GAL and G-Ach, see RFC 5586, MPLS Generic Associated Channel.
The following capabilities are supported in the Junos OS implementation of MPLS-TP:
- MPLS-TP OAM can send and receive packets with GAL and G-Ach, without IP encapsulation.
- Two unidirectional RSVP LSPs between a pair of routers can be associated with each other to create an associated bidrectional LSP for binding a path for the GAL and G-Ach OAM messages. A single Bidirectional Forwarding Detection (BFD) session is established for the associated bidirectional LSP.
