Hi Sue
Thank you for your careful shepherd review and for raising these important
questions.
We would like to first clarify a key distinction that may address your core
concern regarding "creating BGP routes from dynamic sources."
Our Draft Does NOT "Create" BGP Routes from Any Source
draft-jiang-idr-sr-policy-composite-path defines BGP extensions to distribute
composite candidate path information. Specifically:
It distributes a composite candidate path "container" that references
constituent SR Policies by color (e.g., "POL100 uses Color 1 with Weight W1 and
Color 2 with Weight W2").
It does NOT create, generate, or install the candidate paths (segment lists or
dynamic paths) of those constituent SR Policies.
Our Draft Is a Complementary Extension to RFC 9830
As stated in Section 1 of RFC 9830:
"The signaling of Dynamic and Composite CPs (Sections 5.2 and 5.3,
respectively, of [RFC9256]) is outside the scope of this document."
Our draft fills this gap by defining BGP signaling mechanisms for Composite
Candidate Paths, which is precisely stated in the Introduction of our -09 draft:
"This document does not alter the existing deployment methods for SR policies;
it only extends BGP to support the distribution of composite candidate paths
based on [RFC9830]."
Who Creates the Constituent Candidate Paths?
The constituent SR Policies (referenced by color) must have their candidate
paths created and distributed independently via:
Mechanism Reference
BGP RFC 9830 (for explicit candidate paths)
PCEP RFC 9862 (for PCEP-delivered paths)
Static Configuration Local CLI/YANG
Our draft does not alter this. It only adds a new sub-TLV (Constituent SR
Policy sub-TLV) to the BGP Tunnel Encapsulation Attribute to carry the
composite candidate path's reference information（section 2）.
Addressing Your Deeper Concern: Dynamic Sources
We understand your concern about instability from dynamic sources (e.g., IGP,
PCEP). To be clear:
--Our draft does not introduce any mechanism to create BGP routes from IGP or
any other dynamic source.
--The composite candidate path itself is static—it is a fixed list of color
references and weights.
--If an operator wishes to ensure stability, they can ensure that the
constituent SR Policies referenced by the composite path are sourced from
explicit (static) configurations or BGP explicit paths.
--If dynamic paths (e.g., via PCEP) are used for constituent policies, that is
the operator's choice and follows the existing RFC 9256 behavior.
To avoid any future misunderstanding, we propose adding some text to Section 1
(Introduction) in the next revision (-10) of the draft.
We hope this clarifies the scope of our draft. Please let us know if you have
further questions.
BR,
Ran
From: SusanHares <[email protected]>
To: 'SPRING WG' <[email protected]>;idr@ietf. <[email protected]>;
Date: 2026年07月11日 00:10
Subject: [Idr] [BGP-SR-TE] Request for information - prior to adoption call for
draft-jiang-idr-sr-policy-composite-path
_______________________________________________
Idr mailing list -- [email protected]
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Greetings Spring and IDR:
Please note that IPR may exist for this technology. If you are participating
in this discussion and know of IPR, please see the IETF IPR rules.
The authors of draft-jiang-idr-sr-policy-composite-path-04 have requested WG
LC. During IETF-125, I spent a lengthy time discussing the issues of creating
BGP routes from any dynamic source (e.g. IGP). The authors indicated that
these BGP composite paths would come from explicit SR Policy Candidate
Policies, which are statically configured.
This document’s abstract states:
SR Policy Architecture [RFC9256] defines the concept of a Composite
Candidate Path. A regular SR Policy Candidate Path outputs traffic
to a set of Segment Lists, while an SR Policy Composite Candidate
Path outputs traffic recursively to a set of SR Policies on the same
headend. This document defines extensions to BGP to distribute SR
policies carrying composite candidate path information. So that
composite candidate paths can be installed when the SR policy is
applied.
The authors have indicated that the source for the composite policy would be
BGP explicit SR Candidate Paths.
The SR policy in the composite path can be distributed
by BGP as described in [RFC9830], by PCEP as described in [RFC
9862], or through static configuration.
I have 3 groups of questions as the shepherd for this draft:
1) Can composite SR Candidate Paths be limited to be created from only explicit
(aka Static) BGP SR Candidate path?
If so, how is it done (technically)?
What text should be found in draft-jiang-idr-sr-policy-composite-path-04 on
this limited?
Is it there?
2) Is the limitation of composite path to specific BGP sources an appropriate
use of the composite concept from SPRING?
3) How does this interact with the PCE composite CPs?
Cheerily, Sue Hares_______________________________________________
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