On Thu, 7 Aug 2008, Mattias Andersson wrote: > I agree bandwidth is the limit, however the reason to use IAX is it is > saving bandwidth. > I am runging 2 Trixbox CE with IAX over a 2 Mbit line. > I have never had any isues with the IAX trunk. > I wish that I could get son good IAX phones to the office, tan would we skip > on Trixbox and run the phones directly over a VPN Chanel. SIP over VPN are > giving more hassle then IAX sound wise.
So As I Understand It... The bandwidth saving on using IAX is using it in a trunk mode - using it on separate phones will use almost as much as SIP phones will. In my (rough calculations!) world, a SIP call uses 80Kb/sec b/w (each way, but we'll quietly ignore thant for now) A single IAX call uses almost the same, (78 according to a quick check on iftop) but in an IAX trunk, each additional call is only adding on about 65Kb/sec - whereas in a SIP world, each additional call is adding on another 80Kb/sec... Or you can have approx. 15 to 20% more IAX calls than SIP calls over the same Internet path, if they're inside an IAX trunk. Lets see if that works: On a 2Mb line: SIP is: 2048/80 = 25 concurrent SIP calls. IAX is: ((2048-80)/65)+1 = 31 concurrent IAX calls. (And 31 calls is 31*50 = 1550 packets a seconds each way, so make sure the router can handle that!) Personally, I tend to suggest to my customers that if they have more than 4 or 5 extensions in one location that they're better off with a "micro" PBX to trunk the calls out - especially if they're making a lots of calls, and a few internal calls (as on NAT it'll bounce the call out & in again )-: This is based on typical UK ADSL line speeds though (up to 420Kb/sec , outgoing speeds on normal lines, 830Kbps on 'business' lines) Although typically what happens is that they want to keep their existing branch-office POTS lines and integrate them into the "system", so they get a mini PBX rather than a micro one! However I did see some more IAX phones recently when looking: Atcom - http://www.voipon.co.uk/voip-ip-telephones-atcom-iax-ip-telephone-c-1_61.html (thats a UK site, obvously) It also irritates me when I see the likes of Snom (and Doro) phones which are Linux based not supporting IAX ... Gordon _______________________________________________ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- AstriCon 2008 - September 22 - 25 Phoenix, Arizona Register Now: http://www.astricon.net asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
