Quote:
Originally Posted by btc
TruPhone has a good diagram of how SIP works (SIP being the standard on how to make calls "over" the internet)
The basic premise is that if you are going to do a phone call from say the UK to the USA you:
* Start the call in the UK
* Get to a SIP router in the UK
* Send via SIP over the internet
* Send the call from a SIP router in the States to the end recipient
Doing this you can see that you would pay a local rate call in the UK and a local rate call in the States, with the internet handling the call inbetween.
As 2xlocal calls is usually cheaper than 1 international call its an attractive way to ring people.
As you can also tell, it should be very rare that doing a UK to UK call would work out cheaper over SIP unless you are using a transport mechanism that costs lots of money (eg. standard mobile rate to a land line @ 25p per minute) |
This is not strictly true.. If you are in the UK and you are making a call to a US land line, you would only pay for the equivalent of a single local call.
1. You initiate a SIP call fro your mobile over Wifi
2. Your SIP provider will route the call over the internet to a SIP server in the US.
3. The SIP server will then use PSTN to route the call to a real telephone.
So here the only real cost is the transfer of call from SIP to PSTN, which only happens in the destination country.
Many SIP providers will allow you to call landlines for free or almost next to no cost, which is cheaper than a regular land line call.
The call can be made completely free, if you were calling someone else with a SIP capable device.
Anand
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