[spring] Re: following-up discussion on draft-liu-spring-aggregate-header-limit-problem

[[e-mail]]

Hi Jeff,

Yes, strictly speaking, the meaning of some existing MSD types do not fully conform to the original “Maximum SID Depth” definition (but it has to be admitted that all of them are related to the number of SIDs/labels to some extend), and we're using them without misunderstanding. 

Thanks,
Yao


Original


From: JeffTantsura <[e-mail]>
To: 刘尧00165286;
Cc: Eric Vyncke (evyncke) <[e-mail]>;Alexander Vainshtein <[e-mail]>;spring <[e-mail]>;
Date: 2024年08月13日 04:19
Subject: [spring] Re: following-up discussion on draft-liu-spring-aggregate-header-limit-problem

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Hi Yao,
I think as long as the new type name is coherent, MSD could be used as a generic acronym without much harm.
I don’t see any ambiguity with the new MSD-types defined - https://www.iana.org/assignments/igp-parameters/igp-parameters.xhtml#igp-msd-types

Thanks,
Jeff
On Aug 1, 2024, at 17:35, [e-mail] wrote:

Hi Eric, Jeff and Sasha,

Thank you all for the interest and comments on draft-liu-spring-aggregate-header-limit-problem during the presentation on last week's SPRING meeting.
Here're the following-up responses to the comments and some related information on this work.

Comments from Eric: 
Refering to RFC9098 instead of RFC8883 on aggregate header limit. 
Response: 
We've checked RFC9098 after the meeting, but haven't found any formal description on aggregate header limit. So we still have to refer to RFC8883 when it comes to the definition of aggregate header limit. But RFC9098 provides some detailed information on intermediate systems processing Layer 4 information, in this case it needs  process the entire IPv6 header chain as well. We'll add RFC9098 as a reference for this scenario.

Comments from Jeff&Sasha: 
MSD(IGP/BGP/YANG) has provided a mechanism for node's processing limit info advertisement and collection, and it is well defined, a new MSD type for AHL or similar mechanism can meet the requirement.
Response: 
In fact, we've already written a draft draft-liu-lsr-aggregate-header-limit, and the basic idea is defining a new MSD type so the existing mechanism for MSD can all be leveraged. 
It has been discussed on the LSR list and presented in LSR IETF119, but the objection of this approach is that, AHL is a none-routing info, it should not be advertised along with the route advertisement like MSD(although MSD already did that). A suggestion is to leverage the non-routing information signaling mechanism in IGP (draft-ietf-lsr-ospf-transport-instance, RFC6823) for AHL advertisement.
You can find the discussion around the this draft in the lsr minutes [https://datatracker.ietf.org/doc/minutes-119-lsr-202403210300/#signaling-aggregate-header-size-limit-via-igp] and the chatlog [https://datatracker.ietf.org/doc/chatlog-119-lsr-202403211300/] on IETF119. 


Thanks,
Yao