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Re: [spring] Spirit and Letter of the Law (was: Question about SRv6 Insert function)

Fernando Gont <fgont@si6networks.com> Thu, 05 September 2019 15:06 UTC

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To: Robert Raszuk <robert@raszuk.net>
Cc: Robert Raszuk <rraszuk@gmail.com>, Suresh Krishnan <suresh.krishnan@gmail.com>, "6man@ietf.org" <6man@ietf.org>, Ole Troan <otroan@employees.org>, "Joel M. Halpern" <jmh@joelhalpern.com>, "spring@ietf.org" <spring@ietf.org>
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From: Fernando Gont <fgont@si6networks.com>
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Subject: Re: [spring] Spirit and Letter of the Law (was: Question about SRv6 Insert function)
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On 5/9/19 17:46, Robert Raszuk wrote:
> Quote from RFC8200:
> 
>    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.

At the time the packet is created, the Destination Address of course
identifies the destination node.

The very speficication of the Routing Header says:
   The Routing header is used by an IPv6 source to list one or more
   intermediate nodes to be "visited" on the way to a packet's
   destination.


So each of those intermediate nodes are part of the packet delivery
path, and are not allowd to do EH insertion.

As noted, draft-ietf-spring-srv6-network-programming-01 has a normative
reference to voyer-6man-extension-header-insertion for a reason.

I hope things are clear now.



> if IPv6 packets can be legally encapsulated or not. Is encapsulation 
> not an event of sourcing effectively a new packet with some payload ? 

Yes. If you create a new packet, and you put your own address in the SA
of the packet, and encapsulate what you received in the IPv6 payload,
you're free to generate as many EHs as you wish.

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492

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