Hi, >[Please keep discussion of INFO to the SIP list. Copied to >the SIPPING list because this message touches upon SPITSTOP. >Please keep discussion of SPITSTOP to the SIPPING list.] > > >Let us take the case of Malicious Indicator. This is where a >subscriber receives a call, realizes it is a malicious call >(threatening, SPIT, etc.). >They then press the SPIT button (or press *xx), which tells >their service provider to mark the UAC as a bad actor. One >framework proposed for this is the SPITSTOP Reference >Scenario, draft-niccolini-sipping-spitstop-00.txt. > >One might be tempted to think that INFO would be a great >option for this service. It follows the return path of the >INVITE, and so the INFO will hit the caller's inbound proxy, >which it can learn the caller is (statistically) a bad actor. >That way the inbound proxy can do stuff like notify law >enforcement, add a vote to "this is a SPIT source," or other >useful action. > >However, consider a few issues. First, since INFO lives >exclusively within an established dialog, there is no way to >assert this message after the call completes. Second, this >mechanism *relies* on an active service provider topology. >If there is no proxy in the chain that will eat the INFO, the >caller will see the "this is a bad guy" message, which may >have consequences in the real world. Third, there is no >a'priori way for the UAS to know whether or not it can issue >the INFO. The caller CERTAINLY will not advertise, "please >tell me if I am bad, particularly I know in advance that I >*am* a bad actor."
This is an example of a special case, where you don't want to INFO to go "all the way back", ie you want it to be terminated somewhere along the dialog path, and I don't think that is a valid justification why you couldn't use INFO in cases where you don't have that issue. I don't even think this behavior would be allowed according to the proxy rules, so the proxy would more or less be a B2BUA in this case. So, if the outbound proxy supports this mechanism, and DOES want to use INFO, it can insert application/mal-ind in the Accept header before forwarding it towards the UAS (since it is acting as a B2BUA, it is allowed to do so). >What is the correct way of doing this? Here is where we have theory and practice. > >Theory says the proxy needs to SUBSCRIBE for the SPIT event >at the UAS. At this point, life is good, interoperable, and >works across networks. This enables events after the dialog >is torn down, as presumably the SPIT event will refer not to, >"this dialog," which does not exist, but to "that dialog >identifier," which exists (and is theoretically unique) forever. > >[PLEASE TURN YOUR FLAME THROWERS OFF AT THIS POINT] Practice >is that service providers might be able to add value by >providing proprietary phones or IAD's to their subscribers >that just "know" they have an implicit subscription for this >service. Yes, there is a whole host of problems with this, >but if you are in a controlled, limited, no desire for >inter-network connectivity, this mechanism will work. >Moreover, by creating, in this case, a SPIT event package, it >will even allow the *possibility* of interoperable interworking if the endpoints >implement the full SUBSCRIBE protocol. > >This approach shuts down the, "Oh, but with INFO I can save 3 messages, even though this all happens after the call >connects so it adds no user-visible delay" argument. I am a little confused. I thought YOU have been saying that we shall define mechanisms which are NOT based on behavior in controlled and limited networks... Regards, Christer _______________________________________________ Sip mailing list https://www1.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
