There’s no objection against policies installed at ingress interfaces to an SR 
domain. Rob correctly states, that the SR architecture does not require per 
path state at transit nodes. And that’s good and correct. I’d like to see the 
number of signaling protocols in the SR core network being reduced as compared 
with today’s MPLS network, not increased.

There’s RSVP-TE for MPLS, which can be deployed for services requiring per path 
state at transit nodes.

Regards,

Ruediger

Von: spring [mailto:spring-boun...@ietf.org] Im Auftrag von Stewart Bryant
Gesendet: Dienstag, 19. Juni 2018 13:19
An: Rob Shakir <robjs=40google....@dmarc.ietf.org>; SPRING WG List 
<spring@ietf.org>
Betreff: Re: [spring] Updating the SPRING WG Charter




On 01/06/2018 17:05, Rob Shakir wrote:
The SPRING WG defines procedures that allow a node to steer a packet through an
SR Policy instantiated as an ordered list of instructions called segments and
without the need for per-path state information to be held at transit nodes.

I am not sure where the line gets drawn with the per-path state statement. If I 
introduce a
binding-SID to allow the creation of a path, have I introduced per-path state 
or not? In practise
a management entity will choose between the infinity of possible binding-SIDs 
by considering
the need to create specific paths and I would imagine that many will be 
instantiated just-in-time.

I think that the key point is that the ingress creates the path by using SIDs 
to create
a concatenation of paths, policies and resources. However it could be argued 
that
as soon as we introduced Binding SIDs we introduced per-path state. I think we 
might
be best served by deleting the text I have highlighted.

- Stewart




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