Many companies provide SIP "termination" (outbound calling) and "origination" (inbound calling, usually with a POTS phone number, called a DID). Most companies that provide one, provide the other.

Outbound (termination) rates vary from provider to provider and can often depend quite a bit on the kind of number being called. For example, since European cell phones have "calling party pays" billing, calling a London cell number can cost over US$0.20/minute, while calling a London landline can cost under US$0.01/minute^[1].

Inbound calling prices are more varied, particularly in the US. Some providers offer flat rate pricing "per channel" (simultaneous call leg) while some offer an unlimited number of channels but a low, fixed per-minute rate. Some providers offer a choice of plan.

In both cases, a SIP-compatible softphone or softswitch is configured to place certain (or all) outbound calls through the SIP provider; likewise, the switch or softphone is configured to register with the SIP provider to be notified when a new inbound phone call is available to answer.

[edit] List of SIP providers

This is a very incomplete list of providers; other lists that are currently kept better up-to-date are available on the web^[2][3][4][5].

• sipgate
• voipcheap
• voipstunt
• smsdiscount
• iptel

[edit] References

1. ^ http://voip.ms/rates.php
2. ^ http://www.voip-info.org/wiki/view/VOIP+Service+Providers
3. ^ http://www.myvoipprovider.com/Residential_VoIP_Comparison
4. ^ http://www.sipcenter.com/sip.nsf/html/Service+Providers
5. ^ http://www.dslreports.com/reviews

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