[mpls] Comments on draft-gandhi-mpls-rfc6374-sr

Tarek Saad <tsaad.net@gmail.com> Sun, 17 November 2019 07:07 UTC

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From: Tarek Saad <tsaad.net@gmail.com>
To: "draft-gandhi-mpls-rfc6374-sr@ietf.org" <draft-gandhi-mpls-rfc6374-sr@ietf.org>
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Subject: [mpls] Comments on draft-gandhi-mpls-rfc6374-sr
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Hi authors,

Having gone over this draft, I have the following comments:

  1.  Section 6.1.1 introduces a new block number TLV. The claim is RFC8231 requires identification of block number for proper LM. From looking at RFC8231, I see the AM method can be achieved with only 2 colors and many blocks (see section 3.1 of RFC8231).. Given coloring for AM method can be done using SFL (draft-ietf-mpls-sfl-framework) with SFL labels, is this block number TLV still needed?
  2.  Section 4.3.2.1 introduces Return Path subtlv that is suposed to carry the label stack or return path: 1) a similar return path tlv is proposed in other drafts e.g. for use with BFD over SR paths, LSP ping etc. – does it make sense to have unified definition of this return path TLV? b) Figure 7B mentions Segment-List (1) to Segment-List(n) , did you mean Label(1)/Segment(1) to Label(n)/Segment(n)?
  3.  Section 8) lightly talks about ECMP and loose SIDs in end-to-end PM measurement – however, a) it is not clear how end-to-end LM is results are reliable when ECMP is present? b) Similarly, for DM when ECMP for loose SID(s) exists – how delay of each of the ECMP(s) are discovered or at least what sender is doing to ensure all ECMP(s) are traversed by probes?

Regards,
Tarek