> -----Original Message----- > From: Dean Willis [mailto:[EMAIL PROTECTED] > > On Nov 1, 2007, at 3:20 PM, Michael Procter wrote: > > > Whilst having the RFC2833 arriving in the timestamped audio stream > > is certainly beneficial, it is also true to say that the RTP stream > > generally travels quicker than signalling. One of the main reasons > > for this is that the RTP usually travels point-to-point, whilst the > > signalling path often includes a couple of proxies. Even if the > > proxies process the messages in zero time (which they don't), there > > are still multiple network hops introduced as a consequence. > > Additional delays incurred by the proxies/other intermediate > > signalling elements swiftly add up too. > > I agree that this sounds correct in theory. > > What I'm wondering about is those deployments that use media-path > control elements (aka SBCs that police media) and/or decoupled media > and signaling processors. > > I suspect that that SBCs slow down RTP about as much as they slow > down SIP. COuld be more, could be less -- I don't really know.
Uh, nope. There are such things as software-based SBCs, for enterprises and such, but most of the provider ones use dedicated hardware to handle RTP/RTCP. (using NPs/ASICS/whatever) It's not discernibly slower than a router, depending on the vendor. > We don't really use DTMF much between "traditional SIP endpoints" -- > the kind of all-in-one device that does everything in a dedicated > general-purpose processor. It seems that in practice we use it more > frequently in transactions that involve large-scale decoupled > gateways and decoupled media servers, at least at one end of the > call. I wouldn't be surprised to see the practical reality collide > with the theory around 2833. Yeah, I buy that. My worry though isn't about speed. It's about use. One of the obvious use cases for signaling-based DTMF is it follows the signaling, and the media doesn't need to. For an info-dtmf model, that essentially means something in the middle that wants dtmf (an app-server, for example) has to act as a b2bua for signaling, but doesn't need to be in the media path. So even if both info-dtmf and 2833 get negotiated, you'd want to use the info-dtmf. Although I guess if the app-server needed it that way, it would have to have removed 2833 from SDP (yuck), 'cause otherwise as a UA it's essentially lying by offering 2833. -hadriel _______________________________________________ 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
