Using the Generic Associated Channel Label for Pseudowire in the MPLS Transport Profile (MPLS-TP)
updates
- rfc-5586 — MPLS Generic Associated Channel
Extracted elements (6)
RFC 5586 prohibited GAL use with MPLS-TP PWs while allowing it for MPLS PWs, creating an inconsistency. This inconsistency caused unnecessary implementation differences and conflicted with MPLS-TP interoperability requirements (RFC 5654), motivating the removal of the restriction.
MPLS-TP mechanisms must interoperate with existing IETF MPLS (RFC 3031) and PWE3 (RFC 3985) architectures. The prior RFC 5586 restriction on GAL usage with MPLS-TP PWs was inconsistent with this interoperability requirement.
In MPLS-TP, the GAL MAY be used with PWs. This updates RFC 5586, which previously stated the GAL MUST NOT be used with PWs in MPLS-TP environments.
In MPLS-TP, the GAL MUST be used with packets on a G-ACh on LSPs, Concatenated Segments of LSPs, and with Sections. This requirement is unchanged from RFC 5586.
The presence of a GAL in the label stack indicates that an ACH (Associated Channel Header) immediately follows the MPLS label stack. This invariant applies when GAL is used with PWs.
There are no further security considerations beyond those already specified in RFC 5586. The update to allow GAL with PWs in MPLS-TP does not introduce new security concerns.