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

[Huaimo Chen <[e-mail]>]

Hi Shraddha,

    Thank you for the reply.

    My responses are inline below with [HC].

Best Regards,
Huaimo
________________________________
From: Shraddha Hegde <[e-mail]>
Sent: Friday, January 28, 2022 12:05 AM
To: Huaimo Chen <[e-mail]>; [e-mail] <[e-mail]>; SPRING WG <[e-mail]>
Subject: RE: WG adoption call - draft-hu-spring-segment-routing-proxy-forwarding


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.

[HC]: It provides more protection coverage in some cases as compared to

the existing WG adopted draft. This improves the reliability of networks,
and QoE. This is a significant benefit.





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.

[HC]: There is no solution for BSID protection in your draft yet even though

you say that it can be solved using context tables ....

The solution for BSID protection in our draft has been there for a couple of years.



    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.)

[HC]: How do you protect transit node failure using anycast SID in general?

It seems very hard. Your draft seems talking about some specific cases

for a given/specific network topology.



    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.

[HC]: Can you give a simple example for node failure and SR path with the SID of the node,

in which your solution does not have the bandwidth double booking and ours

has the bandwidth double booking?



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://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Furldefense.com%2Fv3%2F__https%3A%2Fnam11.safelinks.protection.outlook.com%2F%3Furl%3Dhttps*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%26data%3D04*7C01*7Chuaimo.chen*40futurewei.com*7Cf11b3573b9f441267f6008d9e164cfef*7C0fee8ff2a3b240189c753a1d5591fedc*7C1*7C0*7C637788645400164200*7CUnknown*7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0*3D*7C3000%26sdata%3DS2*2BmuO29w3Yy*2F3pqvU1A2xByY7xrciCzp*2FUqZfPPUN4*3D%26reserved%3D0__%3BJSUlJSUlJSUlJSUlJSUlJSUlJSUlJSUlJSUlJQ!!NEt6yMaO-gk!XMSkGU0Zm98twzSzoy2RDjLw78tzsjdPlxfqK9Lg-anMbxc8t7yOyePOmhMHgiwU%24&data=04%7C01%7Chuaimo.chen%40futurewei.com%7C0bfa69e2a58f4e67fc4e08d9e21bdeb1%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637789431628757806%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=KXIjLcfaCgjy0tmelCAQSyiteEJHHJvGMQvqGbnZHug%3D&reserved=0>



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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