Re: [spring] WG adoption call - draft-hu-spring-segment-routing-proxy-forwarding

[Shraddha Hegde <[e-mail]>]

WG,

I  don't support the adoption of this document as a WG document.

I am in agreement with stephane's comments on the list.


  1.  May cause congestion somewhere else in the network
There is already WG adopted document that is addressing the problem space
draft-ietf-spring-segment-protection-sr-te-paths.
This draft does not provide significant advantages over the proposed solutions in
draft-ietf-spring-segment-protection-sr-te-paths.
draft-hu-spring-segment-routing-proxy-forwarding claims to provide better solution when all nodes
have not been upgraded. draft-hu-spring-segment-routing-proxy-forwarding introduces protocol extensions
and the nodes that aren't upgraded to understand the extensions will drop the traffic so there isn't
any significant improvement in the approach.

In fact, the approach described in draft-hu-spring-segment-routing-proxy-forwarding may
cause other issues such as bandwidth double booking since it proposes that  any neighbor that
claims proxy forwarding will be used to forward the protected traffic.

For ex:

[cid:[e-mail]14C10]

In above diagram
SR-TE path is RT1->RT3->RT7->RT5
Only RT4 supports proxy-forwarding
On failure of RT3, RT1 would send traffic to RT4 via RT1->RT6->RT7-RT4
RT4 will then send to RT7 as per the SR-TE path
RT7 will then send to RT5 via RT7->RT4->RT5

In this example, same traffic is traversing the RT7->RT4 link 3 times.

Operationally this solution is very complex to manage. A network that starts with no segment protection,
It may be ok to drop the traffic if some nodes have not been upgraded but causing congestion
somewhere else would be difficult to debug.


  1.  BSID solution
draft-ietf-spring-segment-protection-sr-te-paths does not explicitly discuss the solution for BSIDs.
Most of the BSID deployments use anycast based solution where same BSID is assigned on anycast nodes and BSID is always preceded by the anycast SID. Section 2.2 in draft-ietf-spring-segment-protection-sr-te-paths discusses this approach.
             draft-hu-spring-segment-routing-proxy-forwarding  provides a protection solution for BSIDs when anycast is not in use.

 If WG is inclined to solve the BSID protection problem when anycast solution is not in use, I would prefer the
              Approach to be more aligned with draft-ietf-spring-segment-protection-sr-te-paths. I do not support Introducing completely   different solution based on proxy forwarding which has other implications described in point 1.


Rgds
Shraddha



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From: spring [e-mail]<mailto:[e-mail]> On Behalf Of [e-mail]<mailto:[e-mail]>
Sent: Thursday, January 13, 2022 3:49 PM
To: SPRING WG <[e-mail]>
Subject: [spring] WG adoption call - draft-hu-spring-segment-routing-proxy-forwarding

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Dear WG,

This message starts a 2 week WG adoption call, ending 27/01/2022, for draft-hu-spring-segment-routing-proxy-forwarding
https://datatracker.ietf.org/doc/draft-hu-spring-segment-routing-proxy-forwarding/<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/draft-hu-spring-segment-routing-proxy-forwarding/__;!!NEt6yMaO-gk!TWaV4x51MCL2h93fiW-3XI8ElTsP963AWA5gjKCMU6g9E1WN0cRkqV6D5Qi50WbR$>

After review of the document please indicate support (or not) for WG adoption of the document to the mailing list.

Please also provide comments/reasons for your support (or lack thereof) as this is a stronger way to indicate your (non) support as this is not a vote.

If you are willing to work on or review the document, please state this explicitly. This gives the chairs an indication of the energy level of people in the working group willing to work on the document.

Thanks!
Bruno, Jim, Joel

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