Re: [spring] C-SIDs and upper layer checksums (draft-ietf-spring-srv6-srh-compression)

[Joel Halpern <[e-mail]>]

There are two cases covered in section 6.5 of the compression draft that 
appear to be at variance with secton 8.1 of RFC 8200.

First, if the final destination in the routing header is a compressed 
container, then the ultimate destination address will not be the same as 
the final destination shown in the routing header.

Second, if a uSID container is used as the destination address and no 
SRH is present, then in addition to the above problem there is no 
routing header to trigger the behavior described.

Yours,

Joel

On 4/3/2024 4:22 PM, Robert Raszuk wrote:
> Hi Alvaro,
>
>     Section 6.5 of draft-ietf-spring-srv6-srh-compression describes the
>     behavior when an originating node inside an SRv6 domain creates a
>     packet with a C-SID as the final destination. _This description
>     differs
>     from the text in Section 8.1 of RFC8200._
>
>
> I would like you to clarify the above statement - specifically of the 
> last sentence.
>
> Reason for this that after looking at both drafts I find section 6.5 
> of the subject draft to be exactly in line with RFC8200 section 8.1 
> especially with the paragraf which says:
>
> *         If the IPv6 packet contains a Routing header, the Destination
>          Address used in the pseudo-header is that of the final
>          destination.  At the originating node, that address will be in
>          the last element of the Routing header; at the recipient(s),
>          that address will be in the Destination Address field of the
>          IPv6 header.
> *
>
> So before we dive into solutions (as Andrew has already provided a few 
> of) I think we should first agree on what precise problem are we 
> solving here ?
>
> Many thx,
> Robert
>
> PS. As a side note I spoke with my hardware folks - just to check if 
> validation of upper-layer checksum is even an option for transit 
> nodes. The answer is NO as most data plane hardware can read at most 
> 256 bytes of packets. So unless there is some specialized hardware 
> processing up to 9K packets in hardware at line rates this entire 
> discussion about checksum violations, fears of firing appeals is just 
> smoke.
>