Thanks Pablo.
Given that I know some folks read it differently, could we add some
additional text.
Maybe in 3.1, after the sentence you quote about FUNCT, add "The means
of associating the behaviors defined in this document with specific
FUNCT bit patterns is outside the scope of this document."
And in section 9.2, could we add: "This registry is established to
provide consistency for control means which need to refer to these
behaviors. It does not represent encodings within SIDs?"
Thank you,
Joel
On 12/19/2019 12:54 PM, Pablo Camarillo (pcamaril) wrote:
Joel,
Thank you for your question. Your original understanding is correct.
The table “SRv6 Endpoint Behaviors” contains behaviors. Behaviors are
not present in the SRv6 SIDs. They are only used in the control plane.
As you requested, here is the relevant piece of text:
Section 2 (Terminology):
SRv6 SID function: The function part of the SID is an opaque
identification of a local behavior bound to the SID. It is formally
defined in Section 3.1
<https://tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-07#section-3.1>of
this document.
SRv6 segment endpoint behavior: A packet processing behavior executed
at an SRv6 segment endpoint.
Section 3.1 (SID Format):
This document defines an SRv6 SID as consisting of LOC:FUNCT:ARG,
where a locator (LOC) is encoded in the L most significant bits of
the SID, followed by F bits of function (FUNCT) and A bits of
arguments (ARG).
...
The FUNCT is an opaque identification of a local behavior bound to
the SID.
The term "function" refers to the bit-string in the SRv6 SID. The
term "behavior" identifies the behavior bound to the SID.
Section 9.2 (IANA)
Table 3: SRv6 Endpoint *Behaviors* Registry
Thank you,
Pablo.
-----Original Message-----
From: spring <spring-boun...@ietf.org> on behalf of "Joel M. Halpern"
<j...@joelhalpern.com>
Date: Thursday, 19 December 2019 at 16:35
To: "spring@ietf.org" <spring@ietf.org>
Subject: [spring] SRv6 Network Programming Endpoint Behavior Registry
In talking with folks, and looking at the draft, I realized that there
were two different interpretations of the Endpoint Behavior Registry.
I can not tell which is intended.
I had assumed, possibly incorrectly, that the list of code points
was a
list of code points to use in routing and control protocols (so all
the
control mechanisms sould have inter-changeable semantics for SRv6
SIDs.
I thus assumed that one would see in routing an advertisement that in
some form said "SID prefix X is serviced by node Y and provides
functionality of Endpoint Behavior Z, with the remaining bits as
defined
in the registry."
Other folks have read this text as defining the bits that must
appear in
the explicit SID in the SID list, between the loactor portion and the
arguments. This would provide some small savings in the routing and
control infrastructure (but not a lot since there still need to be
advertisements about what Endpoint Behaviors each node actually
supports.) This would seem to constrain implementations to use
exactly
these code point. I am reminded of diffserv, where we looked at doing
that and concluded that operator needs were such that it did not make
sense to mandate the on-the-wire code point.
Can the authors please clarify which meaning they intend? Possibly by
pointing me at the wording in the document that makes it clear?
Thank you,
Joel
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