Robert Sparks wrote:
The thing you describe is not a proxy :)
Seriously, we don't put a lot of work into specifying behavior when
things violate the specification.
I'd be willing to add a paragraph of general tone noting that the loop
detection mechanism breaks if you remove other people's vias.
That works for me.
The technique is in widespread use. Often the things doing it are
clearly B2BUAs (though that doesn't mitigate the looping problem), but I
have certainly heard of things that are otherwise proxies that do this.
I think it behooves us to point out when techniques that people think
are reasonable actually cause real problems.
(If there were two of the things you describe in the network, removing
each other's vias, then there is no hope of ever detecting a loop).
Right. :-(
Paul
RjS
On Jul 20, 2007, at 5:20 PM, Paul Kyzivat wrote:
Just catching up :-(
One thing occurred to me - this document goes out of its way to say
that a proxy need not do the loop check unless it forks. In general
that makes sense, but in one case it does not:
Some proxies hide/suppress/obfuscate via headers, and then reverse the
process on responses. A proxy that does so breaks loop checking by any
of the proxies whose vias it hid. So I think a proxy that does this
MUST perform a loop check itself even if it does not fork.
Thanks,
Paul
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