Hi Shraddha:
Thanks for your comments, Please see inline.
Thanks
Zhibo Hu
From: spring [mailto:[email protected]] On Behalf Of Shraddha Hegde
Sent: Thursday, January 27, 2022 3:15 PM
To: [email protected]; SPRING WG <[email protected]>
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:[email protected]]
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.
------》[HZB] Traffic detour may exist in all local FRR mechanisms and is not
unique to this solution, including TI-LFA.SR-TE Path protection etc，
The solution described in
[draft-ietf-spring-segment-protection-sr-te-paths] also has this problem.for
example you have mentioned,
If using the solution of [ draft-ietf-spring-segment-protection-sr-te-paths],
On failure of RT3, If the last calculated reachable path to RT3 is
RT1->RT6->RT7->RT4->RT3, RT1 maintains the path of RT1->RT6->RT7->RT4->RT3 for
forwarding during the Holdtimer period. Then, RT4 performs Proxy Forwarding and
RT1->RT6->RT7->RT4->RT7->RT4->RT5. It also traverses the link 3 times from RT7
to RT4.
I think extending the protocol is a much simpler way than slow route deletion
and loop solving.
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.
------》[HZB]I don`t think that most of the BSID deployments use anycast based
solution，Strict path control is required in most scenarios, and anycast is not
introduced.
If Bsid is not addressed, it will not be a complete protection
solution.
Rgds
Shraddha
Juniper Business Use Only
From: spring [email protected]<mailto:[email protected]> On Behalf
Of [email protected]<mailto:[email protected]>
Sent: Thursday, January 13, 2022 3:49 PM
To: SPRING WG <[email protected]<mailto:[email protected]>>
Subject: [spring] WG adoption call -
draft-hu-spring-segment-routing-proxy-forwarding
[External Email. Be cautious of content]
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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