[mpls] SR-MPLS Service Programming usecase for Open DT

liu.yao71@zte.com.cn Thu, 16 September 2021 09:01 UTC

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Hi DT,

Besides the requirement in NSH Based SFC usecase in the wiki to carry path ID and metadata by embedding NSH in EH.
There's also a need to carry metadata in SR service programming with SR-MPLS data plane.

The reference is draft-ietf-spring-sr-service-programming. SR service programming is a mechanism to achieve SFC in SR-MPLS and SRv6 networks without the use of NSH.

In this draft, there's a requirement to carry metadata in SR-MPLS data plane, some possible methods to carry metadata (e.g, defining an SRH-like header with only the mandatory fields required to carry metadata) and to indicate the presence of metadata(e.g, adding the indication in the semantic of the service SIDs, or introducing a protocol identifier in the MPLS packet) are proposed but not standardized.
As for the path ID, although not mentioned in this draft, I think there's a potential need for it to let the SFFs distinguish between different SFPs.

Maybe after discussion the solution for this usecase is similar to that for NSH Based SFC, but I think this usecase should be taken into consideration.