OzTell (www.oztralia.com) have a web page that’s not for the faint of heart. OzTell provide a VoIP service to which you can add local PSTN number dialing, remote dial-in-dial-out, SIP, IAX trunking for incremental cost.
It’s not immediately obvious from the funky drop down menus, but you need to click on Integrated Phone Service->Phone – Internet Phone Number in order to get a page that will offer the ability to activate IAX trunk registration.
Costs so far are
$6.95 $5.95/month for a two Sydney telephone numbers and $1.95/month for the IAX trunk. Payment is in advance in $20 minimum chunks. Call prices are here, but for Sydney the key prices are currently AU$0.12/call (3600 seconds) to most Australian landlines and AU$0.005/second for call to mobile phones (AU$0.30/minute).
The OzTel local number service comes with two (Sydney-)local “in-dial” (DID) telephone numbers. I have one configured as a fax receiver, so I receive faxes rendered as PDF on that number. I have the other configured as “Internet Phone” which comes through the IAX trunk to my Asterisk box.
Codec support on the IAX trunk seems to be the full range. uLaw, aLaw, G.726, G.729, iLBC, GSM, Speex, H.261 and H.263 are available. I have configured the codec preferences in this order (effective bandwidth shown from here):
- G.726 – 47 or 55Kb/s
- G.729 – 31Kb/s
- iLBC – 28Kb/s
Using a trunk makes bandwidth estimation a little funny. There is an overhead for signalling and encapsulation (I assume), and trunking of more than one call multiplexes multiple audio payloads into one packet for transport to reduce header overhead (I presume).
I still need to check and see how many calls will come through my DID number simultaneously. Certainly the Sipura SPA-3000 supports call waiting incoming from from the DID/trunk.