Re: [Idr] RFC-compliant use of Extended Length for new BGP attributes

Jeffrey Haas <jhaas@pfrc.org> Thu, 13 March 2008 18:50 UTC

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Date: Thu, 13 Mar 2008 14:47:49 -0400
From: Jeffrey Haas <jhaas@pfrc.org>
To: Vishwas Manral <vishwas.ietf@gmail.com>
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Subject: Re: [Idr] RFC-compliant use of Extended Length for new BGP attributes
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On Thu, Mar 13, 2008 at 11:11:24AM -0700, Vishwas Manral wrote:
> >  The packet is well formed.  As you say, by 1771 rules, it is
> >  semantically incorrect.  The only implementation I would expect to do
> >  anything about this would be the ones run by conformance validation tools.
> I agree to all you say. However I would say all implementations
> following RFC1771 strictly would break.

Implementations that strictly followed RFC 1771 wouldn't have
interoperated well with much of the Internet.  Consider the fact that
AS_PATH length is not one of the inputs to route selection.

Also keep in mind that RFC 2119 wouldn't be published for almost 2 more
years after 1771.

It's probably best to keep in mind that 1771 was known to have bugs -
enough bugs for 26 consequent drafts to fix them.  There are still bugs
in 4271 although their magnitude is probably significantly less on an
interoperability basis.  Conformance to the spec to the exclusion of
interoperating with other vendors may earn you friends with the test
tool manufacturers but it certainly won't make your customers happy.

-- Jeff
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