[spring] Beyond SRv6.

Rob Shakir <robjs@google.com> Sun, 04 August 2019 21:04 UTC

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From: Rob Shakir <robjs@google.com>
Date: Sun, 04 Aug 2019 14:03:49 -0700
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Subject: [spring] Beyond SRv6.
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Hi SPRING WG,

Over the last 5+ years, the IETF has developed Source Packet Routing in
NetworkinG (SPRING) aka Segment Routing for both the MPLS (SR-MPLS) and
IPv6 (SRv6) data planes. SR-MPLS may also be transported over IP in UDP or
GRE.

These encapsulations are past WG last call (in IESG or RFC Editor).

During the SPRING WG meeting at IETF 105, two presentations were related to
the reduction of the size of the SID for IPv6 dataplane:

   -

   SRv6+ / CRH --
   https://tools.ietf.org/html/draft-bonica-spring-srv6-plus-04
   -

   uSID --
   https://tools.ietf.org/html/draft-filsfils-spring-net-pgm-extension-srv6-usid-01



During the IETF week, two additional drafts have been proposed:

   -

   https://tools.ietf.org/html/draft-li-spring-compressed-srv6-np-00
   -

   https://tools.ietf.org/html/draft-mirsky-6man-unified-id-sr-03


As we expressed during the meeting, it is important for the WG to
understand what the aims of additional encapsulations are. Thus, we think
it is important that the WG should first get to a common understanding on
the requirements for a new IPv6 data plane with a smaller SID - both from
the perspective of operators that are looking to deploy these technologies,
and from that of the software/hardware implementation.

Therefore, we would like to solicit network operators interested in SR over
the IPv6 data plane to briefly introduce their:

   -

   use case (e.g. Fast Reroute, explicit routing/TE)
   -

   forwarding performance and scaling requirements
   -

      e.g., (number of nodes, network diameter, number of SID required in
      max and average). For the latter, if possible using both SRv6
128-bit SIDs
      and shorter (e.g. 32-bit) SIDs as the number would typically be different
      (*).
      -

   if the existing SRv6 approach is not deployable in their circumstances,
   details of the requirement of a different solution is required and whether
   this solution is needed for the short term only or for the long term.


As well as deployment limitations, we would like the SPRING community to
briefly describe the platform limitations that they are seeing which limit
the deployment of SRv6  In particular limitations related to the number of
SIDs which can be pushed and forwarded and how much the use of shorter SIDs
would improve the deployments .

For both of these sets of feedback if possible, please post this to the
SPRING WG. If the information cannot be shared publicly, please send it
directly to the chairs & AD (Martin).

This call for information will run for four weeks, up to 2019/09/03. As a
reminder, you can reach the SPRING chairs via spring-chairs@ietf.org and
ADs via spring-ads@ietf.org.

Thank you,

-- Rob & Bruno

(*) As expressed on the mailing list, a 128 bit SID can encode two
instructions a node SID and an adjacency SID hence less SID may be required.