Hi Greg,

Please see [ZA] in-line.

Thanks

Regards … Zafar

From: ipv6 <ipv6-boun...@ietf.org> on behalf of Greg Mirsky 
<gregimir...@gmail.com>
Date: Friday, February 28, 2020 at 11:45 AM
To: Robert Raszuk <rob...@raszuk.net>
Cc: John Scudder <jgs=40juniper....@dmarc.ietf.org>, SPRING WG 
<spring@ietf.org>, 6man WG <i...@ietf.org>
Subject: Re: [spring] I-D Action: 
draft-ietf-spring-srv6-network-programming-10.txt

Hi Robert,
thank you for you consideration. Pablo and I had discussed references to OAM in 
the SRv6 network programming draft. Pablo and authors kindly agreed to remove 
all references to OAM and draft-ietf-6man-spring-srv6-oam. As we are discussing 
the network programming draft, draft-ietf-6man-spring-srv6-oam is in WGLC at 
6man. My intention was to work with the authors of SRv6 OAM draft on 
documenting its relationship with PSP. Would that make sense?

[ZA] Agreed!

Regards,
Greg



On Fri, Feb 28, 2020 at 8:37 AM Robert Raszuk 
<rob...@raszuk.net<mailto:rob...@raszuk.net>> wrote:
Greg,

I agree. Moreover I would suggest to add such text that PSP endpoint behaviours 
should or must not be set for any OEM packets. Would that help ?

Thx,
R.



On Fri, Feb 28, 2020 at 5:22 PM Greg Mirsky 
<gregimir...@gmail.com<mailto:gregimir...@gmail.com>> wrote:
Hi Robert,
you've asked about a possible operational drawback of PSP. I think that for OAM 
PSP has decremental effect on the usefulness of performance measurements as 
there's no obvious information to identify the path a packet traversed.

Regards,
Greg

On Fri, Feb 28, 2020 at 2:55 AM Robert Raszuk 
<rob...@raszuk.net<mailto:rob...@raszuk.net>> wrote:
Hi John,

> I have an additional observation, or question, about Dan’s scenario. Almost 
> all communication is bidirectional.
> Presumably this means a router that’s the tail end of an SRv6 path in one 
> direction is the head end in the other.

While your observation is correct that most TCP connections are bidir SR in a 
lot of cases can operate only in one direction. Needless to say it can also be 
used with UDP streaming.

To extend Ketan's OTT video example let me observe that in a lot of 
transactions queries from clients are tiny and do not TE capabilities while 
responses are huge and bursty and may indeed benefit from special handling.

Sure if you think of applications like VPNs than you are right .. regardless of 
the size of the packets proper tagging must occur in either direction - but 
this is just one use of SRv6 perhaps not even the major one.

- - -

Now as one friend just asked me offline - putting all IPv6 dogmas aside - what 
is the technical issue with removing previously applied extension header from 
the packet within a given operator's network ? What breaks when you do that ?

Thx,
R.


On Thu, Feb 27, 2020 at 10:11 PM John Scudder 
<jgs=40juniper....@dmarc.ietf.org<mailto:40juniper....@dmarc.ietf.org>> wrote:
I have an additional observation, or question, about Dan’s scenario... Almost 
all communication is bidirectional. Presumably this means a router that’s the 
tail end of an SRv6 path in one direction is the head end in the other. Doesn’t 
a head end need to add an SRH? If I’ve gotten that right, then we can extend 
Ron’s list with one more item. That is, apparently the ultimate segment 
endpoint:

• Can process a SID, received as an IPv6 DA, on the fast path
• Cannot process an SRH on receipt, even if Segments Left equal 0, on the fast 
path.
• Can add an SRH on transmission, on the fast path

Even though strictly speaking the second and third bullet points aren’t 
mutually exclusive, it’s a little difficult to imagine a real router that would 
have both these properties simultaneously. Perhaps I’m not being creative 
enough in imagining deployment scenarios? Since this scenario is claimed as an 
important reason this problematic feature is needed, it would be great if 
someone who understands it would elucidate, thanks.

One further point, Ron says “I wonder whether it is a good idea to stretch the 
IPv6 standard to accommodate IPv6-challenged devices.” I also wonder this, 
especially because these devices will have a relatively limited lifetime in the 
network.[*] I don’t find the cost/benefit attractive of making a permanent 
detrimental change to the IPv6 architecture to accommodate a temporary 
deployment issue.

Regards,

—John

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