[mpls] Request feedback/comments on draft-liu-6man-icmp-verification

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Hi MPLS,

As we know, SR SIDs can be related with more and more extra information, but unlike FEC validation in MPLS lspping, there's no mechanism to verify the data plane against the control plane for SRv6. This draft proposes extensions to ICMPv6 to achieve similar functions in SRv6 like FEC validation in MPLS lspping.

After the draft being presented in SPRING last IETF, we're suggested to look for suggestions and guidance from MPLS experts.
A main concern we've received last time is that, for lspping fec validation, when a new type of FEC information is related with the MPLS label, a new FEC sub-TLV is introduced, and the LSRs need to be upgraded to support the new FEC sub-TLVs if you want to do validation, which makes it not very implementation friendly, and introducing similar mechanisms in SRv6 may lead to similar problems.

And another key point is above the real requirement/usecase. A feedback we got is that although lspping in widely used in MPLS, but FEC validation function is rarely used because the requirement to verify the data plane against the control plane by sending and receiving messages on the data plane is not that strong, and there're other north-south bound mechanisms to achieve the similar function.

The draft can be found at https://datatracker.ietf.org/doc/html/draft-liu-6man-icmp-verification-04
Any interest, feedback or comments on this topic are more than welcome. 

Thanks,
Yao