Recently VoxCall introduced as an application for Facebook and it has received wide accolade. Now I have not used that application. Still the reviews I have read challenges my understanding of both PSTN and IP networking. So this post has nothing to do with VoxCall, but to elicit some discussion to clarify my understanding.
First some background information on VoxCall based on my understanding: users register their SIP URI with VoxCall; when a user wants to initiate a session with another, VoxCall originates calls to the SIP URIs of both the users and bridging the calls. Both Dan York and Alec Saunders comment on the fact that call routing can be very involved. But what I do not follow is why the call quality need to be affected. After all, the media path can be redirected to the most direct route between the end-points, independent of the path taken by SIP messages. Now here is something we can not do in the PSTN domain. Yes, Voxcall could allow PSTN numbers as well, but then they have to have their resources involved in the call for the duration of the call and the “convoluted routing” could affect the quality of the call.
In this context Alec observes that find-me/follow-me service is not special in IP world, but telcos charge big money (presumably in the PSTN world, as VoIP providers include this in their list of free services). I am of the opinon that this is more to do with the fact that VoxCall has ever so slightly changed the call routine – one calls “VoxCall number”. What happens if a user wants to change the “carrier” from VoxCall to somebody else? Don’t GrandCentrals offer a similar capability in the PSTN domain?
Posted by aswath at November 25, 2007 12:35 AM
Just to clarify. Calls using VoxCall are point to point (they bypass VoxCall). The only time VoxCall proxies voice is if one or both endpoints do not allow the voice stream to be re-negotiated.
VoxCall also allows users to plug-in any SIP based service provider and they are free to chop and change this provider at anytime and as often as they like.
More details can be found here:
http://faq.voxalot.com/action/view/VoxCall
--
Martin
What I find most surprising about the call quality is perhaps that the call quality of so many other solutions is so poor, Aswath. I guess I've gotten used to poor quality VoIP calls. Most of the VoIP services I've used have terrible quality the minute the call hits the PSTN. For whatever reason, that's not the case I've experienced here.
A
Posted by: Alec at November 25, 2007 07:23 AM