[Idr] Re: draft-li-idr-bgpls-sr-policy-composite-path-09.txt

[linchangwang <[e-mail]>]

Hi Sue,

Thank you so much for taking the time to provide such insightful feedback and constructive suggestions.
I will carefully incorporate all of your valuable input into the next version of this draft.
Your guidance is sincerely appreciated.

Thanks,
Changwang

发件人: Susan Hares <[e-mail]>
发送时间: 2025年11月8日 7:24
收件人: linchangwang (RD) <[e-mail]>; idr <[e-mail]>
主题: RE: draft-li-idr-bgpls-sr-policy-composite-path-09.txt

Changwang:

If you are following RFC9830 for encoding, you need to clearly state this in clear language:
State:
1) As in RFC9830, you do not use the Color TLV of the Tunnel encapsulation attribute,
2) The Color extended community is used to forward the traffic into a SR Policy
(that in turn may or may not have an active candidate SR Policy).
3) The color of the Constituent SR Policy is identified by its color.
                      Constituent SR Policy
                          Color
                          Weight
                          Forwarding Class

A bit more explanation is needed on why just color identifies the policy.
Are multiple Segment lists bound in the Constituent policy?

My conclusion from this discussion is that the text needs to be improved
to provide a clear discussion of the functions.

Thank you for the discussion! Keep going.  This is important work.

Sue


From: linchangwang <[e-mail]<mailto:[e-mail]>>
Sent: Friday, November 7, 2025 1:44 PM
To: Susan Hares <[e-mail]<mailto:[e-mail]>>; idr <[e-mail]<mailto:[e-mail]>>
Subject: Re: draft-li-idr-bgpls-sr-policy-composite-path-09.txt


Hi Sue,

Thank you for the detailed explanation of the issue. Please refer to my previous email reply for details: https://mailarchive.ietf.org/arch/msg/idr/hzmhbnprVBh0KcbRsMBOAX-p1P0/.

Currently, 'Color' is defined as a field in the Constituent SR Policy sub-TLV.
The 'color' in the SR Policy attribute is unrelated to the Color Extended Community attribute or Color TLV.
The newly defined 'color' field in draft-li-idr-bgpls-sr-policy-composite-path-09 is introduced under the Constituent SR Policy sub-TLV within the SR Policy attribute.

Alternatively, we could rename it to 'Constituent SR Policy Color' to avoid confusion with these existing color-related terms?

Thanks a lot!

Thanks,
Changwang

发件人: Susan Hares <[e-mail]<mailto:[e-mail]>>
发送时间: 2025年11月8日 1:59
收件人: idr <[e-mail]<mailto:[e-mail]>>
主题: [Idr] draft-li-idr-bgpls-sr-policy-composite-path-09.txt


The question at the microphone related to the discussion
on draft-jiang-idr-sr-policy-composite-path.


The draft-jiang-idr-sr-policy-composite-path does not specify
how the Color precedence works between the setting of
color in the BGP Update by three things:
1) Color extended community attribute
2) Color TLV
3) Segment list’s Constituent SR Policy TLV – Color Sub-TLV

If I were an operator, I would like to BGP-LS
a) What color set by policy on the composite candidate path,
b) Where this color came from (Color Ext. Community,
   Color TLV in Tunnel Attribute, Segment List’s
    Constituent SR Policy TLV).

Does your draft assume BGP and/or the SRPM saves this information?
If so, how does it query for this information?

Cheerily, Sue



Relevant text sections for reference:


draft-jiang-idr-sr-policy-composite-path text that applies:
      SR Policy SAFI NLRI: <Distinguisher, Policy-Color, Endpoint>
          Attributes:
              Tunnel Encaps Attribute (23)
                  Tunnel Type: SR Policy
                      Binding SID
                      SRv6 Binding SID
                      Preference
                      Priority
                      Policy Name
                      Policy Candidate Path Name
                      Explicit NULL Label Policy (ENLP)
                      Segment List
                          Weight
                          Segment
                          Segment
                          ...
                      Constituent SR Policy
                          Color
                          Weight
                          Fowarding Class
                      ...



   The Constituent SR Policy sub-TLV has the following format:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      Type     |         Length              |     RESERVED    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                             Color                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                             Weight                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            sub-TLVs                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                   Figure 1:  Constituent SR Policy sub-TLV format



draft-li-idr-bgpls-sr-policy-composite-path-09.txt

The Composite Candidate Path TLV is used to report the constituent SR
   policy(s) of a composite candidate path.  It is carried in the
   optional non-transitive BGP- LS Attribute defined in [RFC9552] and is
   associated with the SR Policy Candidate Path NLRI type.  Only a
   single instance of this TLV is advertised for a given candidate path.
   If multiple instances are present, then the first valid (i.e., not
   determined to be malformed as per section 8.2.2 of [RFC9552]) one is
   used and the rest are ignored. The TLV has following format:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Type             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            RESERVED                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Color                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Weight                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sub-TLVs (variable)                     //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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