Re: [Users] Detecting runaway calls

Hi, I'd also like to add my 2 cents to this topic, which might be slightly off-topic on this mailing list. Imho the problem discussed here is a major defficiency of the SIP protocol, which forces most vendors to implement proprietary extensions in their equipment. Call supervision is a feature that might not be important for best-effort services, but is of utmost importance when deploying SIP within a commercial environment. Have a look at, e.g. H.323. They do have several redundant mechanisms to detect stale calls (e.g. at H.225 RAS level (IRQ/IRR/IACK/INAK), and at call signaling level (Status request/Status)). These messages offer detailed information on all ongoing calls within a terminal/gateway - either on sending an explicit request or by asking the endpoint to provide this information on a periodical base. Beside this, RRQ/RCF also provides re-registration features similar to REGISTER timers in SIP. Again imho the clean solution for SIP was to have an equivalent of these features defined in the 3261 core. It's too late for this now. What still can (and should) be done is an RFC that defines an extension to SIP which implements call supervision. Concluding: It's obvious that _real_ call supervision that is capable to detect malicious, non-standard compliant terminals (which, e.g. signal voice but send video over the voice channel) requires some border gateways featuring RTP content sniffing. But this is imho no excuse for SIP not providing standardized means capable to supervise calls on standard-compliant SIP devices. regards --Joachim