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Re: Question about Subnet-Router anycast address

François-Xavier Le Bail <fx.lebail@yahoo.com> Mon, 03 October 2011 14:06 UTC

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Date: Mon, 03 Oct 2011 07:08:57 -0700
From: François-Xavier Le Bail <fx.lebail@yahoo.com>
Subject: Re: Question about Subnet-Router anycast address
To: Thomas Narten <narten@us.ibm.com>
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--- On Mon, 10/3/11, Thomas Narten <narten@us.ibm.com> wrote:
> <fx.lebail@yahoo.com> writes:
> 
> > If the source address of reply differs from destination address of
> > the request, some applications are broken. 
> 
> If you are saying that applications should ignore the src
> address (in case it is anycast) when accpting replies, I very
> strongly disagree.

I don't say that.

> The norm is (and has been forever) to require that the
> source address in a response (whether TCP or UDP) match the destination
> address in the original query. And for good reason.

But the RFC 3484, as I understand it, exclude anycast address from the 
source replies.

Section 4 of RFC 3484 states:
    (http://tools.ietf.org/html/rfc3484#section-4)
    4. Candidate Source Addresses
    [. . .]
       In any case, anycast addresses, multicast addresses, and the
       unspecified address MUST NOT be included in a candidate set.

It might be useful to reassess this restriction, at least for the replies.

Thanks,
François-Xavier

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