Re: END SID Without SRH

[Bob Hinden <[e-mail]>]

Darren,

> On Jun 12, 2019, at 2:52 PM, Darren Dukes (ddukes) <[e-mail]> wrote:
> 
> Hello everyone.
> 
> This document defines an SRH and a SID, and how that SID is processed.
> 
> I expect anyone "surprised" by this fact should have read this draft at some point:
> a - within the past 2 years; since this document has defined a SID and its processing.
> b - within the past 13 months; since section 4.3.1 specifically described discarding the packet based on upper layer header being processed.
> c - within the past 8 months; since the current version of 4.3.1.2 was updated with the new ICMP error code, published, and the WG was notified via email.
> 
> And recall section 3.1 defines a Source SR node as 
>   "any node that originates an IPv6 packet with a
>   segment (i.e.  SRv6 SID) in the destination address of the IPv6
>   header.  The packet leaving the source SR Node may or may not contain
>   an SRH."
> 
> In other words, there is no surprise.

I am trying to sort out this discussion. 

I think the text in the draft this discussion is about is:

>  4.3.1.2.  Upper-layer Header or No Next Header
> 
>    When processing the Upper-layer header of a packet matching a FIB
>    entry locally instantiated as an SRv6 SID defined in this document.
> 
>    IF (Upper-layer Header is IPv4 or IPv6) and
>        local configuration permits {
>      Perform IPv6 decapsulation
>      Resubmit the decapsulated packet to the IPv4 or IPv6 module
>    }
>    ELSE {
>      Send an ICMP parameter problem message to the Source Address and
>      discard the packet.  Error code (TBD by IANA) "SR Upper-layer
>      Header Error", pointer set to the offset of the upper-layer
>      header.
>    }
> 
>    A unique error code allows an SR Source node to recognize an error in
>    SID processing at an endpoint.


If I understand it correctly, the case for the action described in this section  is:

   When processing the Upper-layer header of a packet matching a FIB
   entry locally instantiated as an SRv6 SID defined in this document.

A node receiving this packet that knows it is SRv6 SID (because it was locally instantiated), would follow this procedure.   A node who does not know that it is an SRv6 SID, will process the packet normally as defined in RFC8200/etc/etc.

Essentially, a node will only do this if it is in an SRv6 domain because it has had SRv6 SID information configured manually or via some protocol.

Am I correct?

Bob