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

[Shraddha Hegde <[e-mail]>]

Huaimo,



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From: Huaimo Chen <[e-mail]>
Sent: Friday, January 28, 2022 2:39 AM
To: Shraddha Hegde <[e-mail]>; [e-mail]; SPRING WG <[e-mail]>
Subject: Re: WG adoption call - draft-hu-spring-segment-routing-proxy-forwarding

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Hi Shraddha,

    Thank you for your comments.

    I remember that I talked to you face to face in IETF meeting and
suggested merging your draft and our draft a long time ago before
your draft is adopted. You said it would be ok to have the two drafts
in WG.
<SH> I honestly don't remember the conversation. I would be OK with two drafts
If the proxy forwarding was adding value but I see that it has no significant benefits
As compared to the existing WG adopted draft.


In addition, I sent you an email to ask for merging the two drafts,
but did not receive any reply from you.

    I also remember that Zhibo supported the adoption of your draft.

    These two drafts have some overlaps and differences. Our draft
refers to yours for the overlaps, but focuses on the different
method for protection and the area your draft does not cover.
<SH> BSID protection when anycast is not in use is the area your draft
Covers and is not covered by draft-ietf-spring-segment-protection-sr-te-paths.
proxy forwarding is a solution that overlaps existing solution space and is completely different
from existing solution space. For BSID protection, proxy forwarding is not necessary.
It can be solved using context tables by learning the details of the BSID from neighbors.
It would be good to see how many operators are really interested in this kind of BSID protection.


    For example, your draft talks about using anycast SID to protect
node failure. I remember that this was discussed in IETF meeting and
some issues were raised by others.
<SH> There are no open issues AFAIKT.
We do not use anycast SID for
protection.
<SH>The draft draft-ietf-spring-segment-protection-sr-te-paths  proposes
anycast SID as one of the ways to achieve protection (It is the most common deployed
mechanisms to achieve protection in SR networks in my knowledge.)

    Regarding to "May cause congestion somewhere else in the network",
this seems true for the two drafts when a node failed.
<SH> The issue I brought up was more for the bandwidth double booking on interfaces and it
May happen in proxy forwarding as the proxy forwarder may not lie in the shortest path
But may be on the otherside.

Best Regards,
Huaimo

________________________________
From: spring <[e-mail]<mailto:[e-mail]>> on behalf of Shraddha Hegde <shraddha=[e-mail]<mailto:shraddha=[e-mail]>>
Sent: Thursday, January 27, 2022 2:15 AM
To: [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>; SPRING WG <[e-mail]<mailto:[e-mail]>>
Subject: Re: [spring] WG adoption call - draft-hu-spring-segment-routing-proxy-forwarding


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]09380]



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.



2.       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]<mailto:[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:/nam11.safelinks.protection.outlook.com/?url=https*3A*2F*2Furldefense.com*2Fv3*2F__https*3A*2Fdatatracker.ietf.org*2Fdoc*2Fdraft-hu-spring-segment-routing-proxy-forwarding*2F__*3B!!NEt6yMaO-gk!TWaV4x51MCL2h93fiW-3XI8ElTsP963AWA5gjKCMU6g9E1WN0cRkqV6D5Qi50WbR*24&data=04*7C01*7Chuaimo.chen*40futurewei.com*7Cf11b3573b9f441267f6008d9e164cfef*7C0fee8ff2a3b240189c753a1d5591fedc*7C1*7C0*7C637788645400164200*7CUnknown*7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0*3D*7C3000&sdata=S2*2BmuO29w3Yy*2F3pqvU1A2xByY7xrciCzp*2FUqZfPPUN4*3D&reserved=0__;JSUlJSUlJSUlJSUlJSUlJSUlJSUlJSUlJSUlJQ!!NEt6yMaO-gk!XMSkGU0Zm98twzSzoy2RDjLw78tzsjdPlxfqK9Lg-anMbxc8t7yOyePOmhMHgiwU$>



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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