Re: [IPv6] [spring] Subject: Mandating SRH when using C-SIDs (draft-ietf-spring-srv6-srh-compression)

Tom,

So let me try to restate your point.

You are saying that such ability to distinguish non encapsulated SR packet
with uSIDs is needed only for devices which would capture some packets in
the middle, trying to run checksum and failing.

Is this so ?

Are there any other reasons for this ?

I am not saying your reason is not important - just trying to make sure it
is clearly spelled out.

Thx,
R.

On Fri, Apr 5, 2024 at 4:31 PM Tom Herbert <tom=
40herbertland.com@dmarc.ietf.org> wrote:

>
>
> On Fri, Apr 5, 2024, 8:53 AM Antoine FRESSANCOURT <antoine.fressancourt=
> 40huawei.com@dmarc.ietf.org> wrote:
>
>> Hello,
>>
>> After reading RFC 8754 and RFC 8986 together with the draft (version 14),
>> it seems to me that the cases when the SRH will be omitted are quite
>> limited, and will happen among nodes sharing the same locator block. We can
>> assume that, in such cases, nodes exchanging packets carrying a C-SID
>> without SRH will be managed by a single entity and that this entity can
>> check whether some middlebox infer with packet relaying.
>
>
> Antoine,
>
> If it's such a limited use case then I have to ask if it's worth the
> effort to make this a robust protocol? All we really need is a
> deterministic way to distinguish SR packets from non-SR packets, which
> could be accomplished by a minimum sized eight byte SRH. In other words, it
> seems like this discussion is only about saving eight bytes on the wire for
> a narrow use case.
>
> Tom
>
>
>>
>> Then we could modify the text to mention that, if such an inference is
>> detected, the packet should use a SRH. In my view, being clear about
>> potential issue related with omitting the SRH and giving an alternative is
>> enough, and gives some freedom to people willing to use C-SID without SRH
>> in their context.
>>
>> Best regards,
>>
>> Antoine Fressancourt
>>
>> -----Original Message-----
>> From: spring <spring-bounces@ietf.org> On Behalf Of Alvaro Retana
>> Sent: jeudi 28 mars 2024 13:06
>> To: SPRING WG List <spring@ietf.org>
>> Cc: 6man <ipv6@ietf.org>; spring-chairs@ietf.org
>> Subject: [spring] Subject: Mandating SRH when using C-SIDs
>> (draft-ietf-spring-srv6-srh-compression)
>>
>> 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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