RE: Extension Header Insertion

["Adrian Farrel" <[e-mail]>]

Hello Darren,

 

Thanks for your considered and friendly reply.

 

Thanks for the additional pointer to 8200. I (of course) was not involved in
the production of that document, but I read it as doing two things:

1.	Setting the high-level behaviour for general processing.
This is the text you quote.
2.	Giving detailed rules about specific EHs for order and presence.
The text I quoted.

 

So I would be guided by 8200 to not expect to see a second routing header
(e.g., SRH).

 

Of course, I might implement to see the second one and treat it as an
unknown EH. That would be good self-protection code.

 

Now, I said "Thus we may assume that the proponents of Extension Header
insertion do think that it is acceptable to insert a second routing header
into a packet that already has one." And you said "I do not agree with your
assumptions". So can I take it that you do not think it is acceptable to
insert a second SRH into a packet that already has one?

 

Thanks,

Adrian

 

From: Darren Dukes (ddukes) <[e-mail]> 
Sent: 09 December 2019 13:31
To: [e-mail]; 'Ron Bonica'
<rbonica=[e-mail]>; '6man' <[e-mail]>
Subject: Re: Extension Header Insertion 

 

Hi Adrian. You failed to quote the section of rfc 8200 where it says "IPv6
nodes must accept and attempt to process extension headers in

   any order and occurring any number of times in the same packet,"

 

I do not agree with your assumptions nor the attempt to imply something
about the Other drafts. 





Darren. 

 

  _____  

From: ipv6 <[e-mail] <mailto:[e-mail]> > on behalf
of Adrian Farrel <[e-mail] <mailto:[e-mail]> >
Sent: Monday, December 9, 2019 4:34 AM
To: 'Ron Bonica'; '6man'
Subject: RE: Extension Header Insertion 

 

Hi Ron,

 

I think we can jump to a quick answer on this because
draft-ietf-spring-srv6-network-programming-05 says:

 

   We assume that the SRH may

   be present multiple times inside each packet.

 

Thus we may assume that the proponents of Extension Header insertion do
think that it is acceptable to insert a second routing header into a packet
that already has one.

 

And 8200 is clear when it says:

   Each extension header should occur at most once, except for the

   Destination Options header, which should occur at most twice (once

   before a Routing header and once before the upper-layer header).

 

So draft-ietf-spring-srv6-network-programming-05 includes a false assumption
which need to be either removed or secured through an update to 8200.

 

Ideally, I suppose, draft-ietf-6man-segment-routing-header would have
contained the clarification that the SRH could be present multiple times
(updating 8200 as it went).

 

Cheers,

Adrian

 

From: ipv6 <[e-mail] <mailto:[e-mail]> > On Behalf
Of Ron Bonica
Sent: 09 December 2019 03:04
To: 6man <[e-mail] <mailto:[e-mail]> >
Subject: Extension Header Insertion 

 

Folks,

 

This question is posed primarily to the proponents of Extension Header
insertion. 

 

Do you think that it is acceptable to insert a second routing header into a
packet that already has one, so the resulting packet looks like the
following:

 

*	IPv6 header
*	SRH
*	SRH
*	Upper-layer header

 

Would this be common in TI-LFA?

 

                                                                      Ron

 

 

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