Re: [Sip] Thoughts on SIP Identity issues

[Hadriel Kaplan <HKaplan at acmepacket.com>]

> -----Original Message-----
> From: sip-bounces at ietf.org [mailto:sip-bounces at ietf.org] On Behalf Of Dan
> Wing
>
> Thank you - this is the first description of a codec attack that
> anyone has explained.
>
> So a beneficial change (adding a codec and doing transcoding for
> the user) is okay, but a non-benficial change (removing a good-
> sounding codec for the end equipment [wideband] or for the network
> [iSAC]) is an attack?

I still don't buy it.  Honestly, exactly how much benefit does an attacker get by "downgrading" your codec?  If there is no benefit/motivation for an attacker, why is this a threat we care about?

Alternatively, there *is* motivation for removing codecs to *improve* your experience - this is in fact done right now in deployed networks, to force calls crossing low-bandwidth WAN links to use lower-bandwidth codecs (e.g., removing g711 in favor of g729, or re-re-ordering them in the m-line).  In those cases the removal is beneficial.

-hadriel
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