Re: [spring] Network Programming - Penultimate Segment Popping

Tom Herbert <tom@herbertland.com> Sat, 07 December 2019 16:26 UTC

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From: Tom Herbert <tom@herbertland.com>
Date: Sat, 7 Dec 2019 08:26:29 -0800
Message-ID: <CALx6S375sPG3jNybNbyA5eAUKTefGy_=LKBcmhfEhc5-B4e1OQ@mail.gmail.com>
To: "Darren Dukes (ddukes)" <ddukes@cisco.com>
Cc: Ron Bonica <rbonica@juniper.net>, SPRING WG <spring@ietf.org>, 6man <6man@ietf.org>
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Subject: Re: [spring] Network Programming - Penultimate Segment Popping
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On Sat, Dec 7, 2019 at 7:10 AM Darren Dukes (ddukes) <ddukes@cisco.com> wrote:
>
> Ron, you say
> >>  RFC 8200 addresses extension header insertion and deletion identically, in the same sentence.
>
> This sentence you refer to clearly permits PSP as defined in network programming:
>    Extension headers (except for the Hop-by-Hop Options header) are not
>    processed, inserted, or deleted by any node along a packet's delivery
>    path, until the packet reaches the node (or each of the set of nodes,
>    in the case of multicast) identified in the Destination Address field
>    of the IPv6 header.
>
> Clearly we process the SRH at the node identified in the destination address field of the IPv6 header.
> With PSP we remove the SRH at the node identified in the destination address field of the IPv6 header.
>
Darren,

I believe you are assuming a very liberal interpretation of the
wording in RFC8200. If intermediate hosts in the routing list are able
to add or remove SRH per RFC8200, then they are allowed to add or
remove any and all extension headers per the same interpretation. I do
not believe that is at all the intent of RFC8200. Also note that the
liberal interpretation it would validate other cases of arbitrary
extension header manipulation like in NAT devices for instance.

Tom

> I think it’s clear we can conclude this thread.
>
> Darren
>
>
>
> On Dec 6, 2019, at 5:01 PM, Ron Bonica <rbonica@juniper.net> wrote:
>
> >> I have observed, in your original post, the conflation of SRH insertion within an SR Domain with the PSP behavior defined in network programming.
> >> Whether this was intentional or not, I do not know.
> >> Regardless, it is wrong.
>
> Darren,
>
> We clearly disagree.  RFC 8200 addresses extension header insertion and deletion identically, in the same sentence.
>
>
>                                                        Ron
>
>
>
>
>
>
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