> As another example that is more complicated, consider > changing codecs. > In one way, codecs are invisible to users. Indeed, a change > of codec for > purposes of transcoding will allow a call to succeed when it might > otherwise fail, and is thus beneficial to users and not harmful. > However, a downgrade of codecs - for example, removing > wideband codecs > from a codec list - is harmful and noticeable to users. If I have a > softclient with iSAC and I call someone else who does too, but we get > only g729, frankly, this is noticeable to the users. Indeed, one can > imagine that if a user of such a soft client sometimes gets > wideband and > sometimes not, they may ask the person on the other end of > the call if > they also have a softclient with the wideband feature, and if that > person does, not understand why there was no wideband for the > call. In > this case, modifications of codecs can be considered an > attack without > some indication to the user why they are not getting wideband.
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? -d _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip
