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

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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