Re: [spring] Suggest some text //RE: Request to close the LC and move forward//RE: WGLC - draft-ietf-spring-srv6-network-programming

Zafar, I seem to have missed something.  I understand how the SRv6 OAM 
works with a SID that happens to be a PSP SID, up until we get to the 
step from the penultimate hop to the ultimate hop.  At the penultiamte 
hop, everything works.  But before getting to the ultimate hop, the SRH 
is stripped.  Therefore, at the ultimate hop no OAM can take place for 
the path with PSP.
If you define the O bit to over-ride the PSP processing, that in and of 
itself means that the packets on that final leg are different, again 
modifying the intended behavior of OAM.

I will be happy if you can explain how you found a way out of this 
conundrum.

Yours,
Joel

On 3/1/2020 8:57 AM, Zafar Ali (zali) wrote:
> Greg, Joel,
> 
> _All_ the existing IPv6 OAM tools (e.g., ICMP, traceroute, TWAMP, BFD, 
> etc.) works “as-is” for the PSP SID.
> 
> They shall exercise the FIB entry for the PSP SIDs, follow the same path 
> as PSP SIDs, etc.
> 
> We can add clarification in the OAM draft.
> 
> Thanks
> 
> Regards … Zafar
> 
> *From: *spring <spring-bounces@ietf.org> on behalf of Greg Mirsky 
> <gregimirsky@gmail.com>
> *Date: *Sunday, March 1, 2020 at 8:32 AM
> *To: *Robert Raszuk <robert@raszuk.net>
> *Cc: *"6man@ietf.org" <6man@ietf.org>, spring <spring@ietf.org>, "Joel 
> M. Halpern" <jmh@joelhalpern.com>, 神明達哉<jinmei@wide.ad.jp>
> *Subject: *Re: [spring] Suggest some text //RE: Request to close the LC 
> and move forward//RE: WGLC - draft-ietf-spring-srv6-network-programming
> 
> Hi Robert,
> 
> yes, the path probably will be the same regardless whether PSP was 
> applied or not. But performance metrics, e.g. packet delay, may be 
> different for OAM and "regular" packets.
> 
> Regards,
> 
> Greg
> 
> On Sun, Mar 1, 2020, 14:08 Robert Raszuk <robert@raszuk.net 
> <mailto:robert@raszuk.net>> wrote:
> 
>     Nope.
> 
>     Node can advertise two SIDs or PSP in a given network may be a well
>     know function (to limit IGP burden) Example: odd SID includes PSP
>     and even SID does not.
> 
>     O*A*M  packets can use on the exact same path but the penultimate
>     hop traversal is directed by even SID and is not subject to PSP..
> 
>     Done.
> 
>     Thx,
>     R.
> 
>     On Sun, Mar 1, 2020 at 5:50 AM Joel M. Halpern <jmh@joelhalpern.com
>     <mailto:jmh@joelhalpern.com>> wrote:
> 
>         Presuming that by "OEM" you mean "OAM", then no, this does not work.
>         If the OAM is intended to monitor a path that has a last SID whose
>         flavor is PSP, then something will break.  The monitoring will
>         monitor
>         something else, or it won't monitor the last hop, or...
> 
>         Given the point that was made that ignoring a source route (SRH or
>         otherwise) with segments-left = 0 is a mandatory behavior of
>         8200, I am
>         really left puzzled as to what use case justifies the contortion
>         of PSP.
> 
>         Yours,
>         Joel
> 
>     --------------------------------------------------------------------
>     IETF IPv6 working group mailing list
>     ipv6@ietf.org <mailto:ipv6@ietf.org>
>     Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
>     --------------------------------------------------------------------
> 