[Idr] draft-liu-idr-srv6-segment-list-optimize-02

[Susan Hares <[e-mail]>]

Yisong, Changwang, Ran, and Yuanxiang:

Thank you for your work on draft-liu-idr-srv6-segment-list-optimize-02.

Your draft presents a problem and a solution.
I’ve included a few things that should be considered in
your next revision.  Please let me know if you have any questions
regarding my comments.

Would you mind answering a few questions:


  1.  Are you implementing this technology change?
  2.  Have discussed this problem with the Spring WG?
  3.  Have you considered what segment types use the

SRv6 SID Endpoint Behavior and Structure Sub-TLV?



It appears that segment types B, I, J, and K.



  1.  Have you considered making the E-Flag a field of flags

with more bits?


  1.  Do you have any update you wish to present at

IDR interim on 9/9/2024?

Cheerily, Susan Hares


Detailed Shepherd Review for:
draft-liu-idr-sr-v6-segment-list-optimize-02

status: individual draft,
Status: Proposed Standard,
version: revision needed (-03)
implementations: unknown
Authors: 4

Shepherd Detailed review

Summary: Text provides SR problem and solution.
Needs a few refinements in -03.

Issue-1: Please rename draft

Please rename draft to:

draft-liu-idr-sr-segment-list-optimize-00.

This renaming will help the idr-chairs more easily track the draft.

Issue-2:  Abstract, English text, clarity of text.

Old text:/
   This document introduces an optimization method for segment list
   arrangement to solve the problem of the penultimate segment node
   being unable to perform PSP behavior when the egress node has both
   End SID and service SID and improve the forwarding efficiency of
   data packets.

New text:/
   This document introduces an optimization method for segment list
   arrangement the SR Policy TLV of the BGP Tunnel Encapsulation Attribute.
   This optimization solves the problem of the Segment Routing's
   penultimate segment node being unable to perform the
   penultimate Segment Pop (PSP) behavior when the egress node has both
   End SID and service SID encapsulated in Segment Routing Header's
   segment List. This solution adds an E-Flag to the SRv6 SID
   Endpoint Behavior sub-TLV carried in Segment List Sub-TLV of
   the SR Policy TLV.

   This optimization can improve the forwarding efficiency of data
   packets when End SID and Service SID are present. /




Issue-2: All sections, remove [draft-ietf-idr-segment-routing-te-policy]
Please replace [draft-ietf-idr-segment-routing-te-policy]
with [draft-ietf-idr-sr-policy-safi].


Issue-3: How does the E-Flag interact with the Segment flags
specified in [draft-ietf-idr-sr-policy-safi] and
[draft-ietf-idr-sr-segtypes-ext]

It seems the B-Flag must be on when E-Flag is set.

V-Flag - SID Verification
B-Flag - SRv6 Endpoint Behavior exist in draft.
A-Flag - presence of SR Algorithm
S-Flag - presence of SR-MPLS or SRv6 SID


From [draft-ietf-idr-sr-segtypes-ext]

V-Flag applies to all Segment Types including the ones introduced by this document.
A-Flag applies to Segment Types C, D, I, J, and K.
 If A-Flag appears with Segment Types A, B, E, F, G, and H, it MUST be ignored.

S-Flag applies to Segment Types C, D, E, F, G, H, I, J, and K.
  If S-Flag appears with Segment Types A or B, it MUST be ignored.

B-Flag applies to Segment Types B, I, J, and K.
  If B-Flag appears with Segment Types A, C, D, E, F, G, and H, it MUST be ignored.

It appears the SRv6 SID Endpoint Behavior and Structure is on segment types B, I, J, and K.


Issue-4: E-Flag as set of Flags and IANA Section

It would be wise to create E-Flag as a set of flags in the reserved section.
As such, it would be useful to create a registry for such flags.