Re: RV: (ipv6mh) hardware support for extension headers

[Brian E Carpenter <brc@zurich.ibm.com>]

Actually this depends on which hw designers you talk to, and how
carefully they read the IPv6 spec before pouring silicon. But fundamentally,
yes, the more rigid the extension header format, the better chance
that new ones can be handled on the fast path.

Also please remember we are designing for fifty years at least. Today's
hw is not the end of the story.

  Brian

Pekka Savola wrote:
> 
> On Mon, 27 Oct 2003, marcelo bagnulo wrote:
> > So this means that in the current situation, a solution based on using
> > extension headers would impose that packets carrying those new extension
> > headers would be diverted through the slow path of every router they go
> > through. Is that correct?
> 
> Not precisely.. only those routers which have to go through the packets
> with these extension headers via an L4 ACL (most ACLs are like that..).
> 
> > The solution for this would be to change all routers (besides all hosts to
> > understand the extension header) or to suffer the performance penalty, is
> > this correct?
> 
> Modulo above, yes.
> 
> > If this is so, i don't know if a solution that uses an extension header in
> > every packet would be acceptable.
> > I think that a solution that only uses extension headers in a few selected
> > packets of a communication would be ok.
> 
> IMHO, extension headers *could* be OK, as long as they'd be done in TLV
> format, and we specify in IPv6 WG that all the future extension headers
> would be done in TLV format, so the implementors could add this to their
> ACL code.
> 
> --
> Pekka Savola                 "You each name yourselves king, yet the
> Netcore Oy                    kingdom bleeds."
> Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

-- 
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Brian E Carpenter 
Distinguished Engineer, Internet Standards & Technology, IBM 

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