I agree with Francois’s point.

Also, if the problem comes from middle box checksum, then I do not believe the 
problem exists.
Why a transit node has the right to do so? If it is not an SRv6 Endpoint node, 
it should not try to do so.

Btw, EU, USA and other countries may have the Easter holiday from 3.30 to 4.1, 
and in China, we have a Tomb Sweeping holiday from 4.4 to 4.6, so few people 
are reading the emails I guess. I nearly miss this email.

Thanks,
Cheng




From: ipv6 <ipv6-boun...@ietf.org> On Behalf Of Francois Clad
Sent: Thursday, April 4, 2024 1:50 PM
To: Alvaro Retana <aretana.i...@gmail.com>
Cc: 6man <i...@ietf.org>; spring-cha...@ietf.org; SPRING WG List 
<spring@ietf.org>
Subject: Re: [IPv6] Subject: Mandating SRH when using C-SIDs 
(draft-ietf-spring-srv6-srh-compression)

Hi Alvaro, all,

RFC 8754 allows the SR source node to omit the SRH when it contains redundant 
information with what is already carried in the base IPv6 header. Mandating its 
presence for C-SID does not resolve any problem because it will not provide any 
extra information to the nodes along the packet path.

Specifically for the case of middleboxes attempting to verify the upper-layer 
checksum,
·        An SRv6-unaware middlebox will not be able to verify the upper-layer 
checksum of SRv6 packets in flight, regardless of whether an SRH is present or 
not.
·        An SRv6 and C-SID aware middlebox will be able to find the ultimate DA 
and verify the upper-layer checksum in flight, regardless of whether an SRH is 
present or not.

Furthermore, transit nodes (e.g., middleboxes) should not attempt to identify 
SRv6 traffic based on the presence of the SRH, because they will miss a 
significant portion of it: all the best-effort or Flex-Algo traffic steered 
with a single segment may not include an SRH, even without C-SID. Instead, RFC 
8402, 8754, and 8986 define identification rules based on the SRv6 SID block.

Thanks,
Francois


On 2 Apr 2024 at 19:44:51, Alvaro Retana 
<aretana.i...@gmail.com<mailto:aretana.i...@gmail.com>> wrote:
[Moving this conversation up on your mailbox. :-) ]

[Thanks, Robert and Tom for your input!]


We want to hear from more of you, including the authors. Even if you already 
expressed your opinion in a different thread, please chime in here.

We will collect feedback until the end of this week.

Thanks!

Alvaro.


On March 28, 2024 at 8:06:18 AM, Alvaro Retana 
(aretana.i...@gmail.com<mailto:aretana.i...@gmail.com>) wrote:

Focusing on the C-SID draft, some have suggested requiring the presence of the 
SRH whenever C-SIDs are used. Please discuss whether that is the desired 
behavior (or not) -- please be specific when debating the benefits or 
consequences of either behavior.

Please keep the related (but independent) discussion of requiring the SRH 
whenever SRv6 is used separate. This larger topic may impact several documents 
and is better handled in a different thread (with 6man and spring included).

Thanks!

Alvaro
-- for spring-chairs
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