Friday 4 February 2011

VoIP and Inter-provider Dialling Codes


I've got an SPA3102 VoIP adaptor, and am frustrated by the lack of proper dialling codes when using VoIP from a normal handset.

I want to be able to dial:

01234 12345678 -> Normal Landline Phone Call
#01234 12345678 -> Normal Phone over Internet
*1001 12345678 -> Call to another VoIP Phone

The problem is this: When you dial a VoIP phone, you dial


A phone number is easy to dial, but the @voipprovider.address is usually impossible to enter from a standard phone handset (which is exactly what you plug into an SPA3102 Analogue Telephone Adaptor)

I've tried sipbroker, as my provider gives you a prefix for it. What sipbroker does is have a directory of VoIP providers, and when you dial *pppnnnnn, it is translated to nnnnn@provider.address. So it's great for dialling out!

The problem is when calls are received. When I get an incomming call, the Caller Line ID (CLID) has the full sending address, but by the time it gets to my phone simply gives me their VoIP account number (i.e. misses off the @voipprovider.address, or *ppp), rather than something I can use to uniquely work out who has called.

I can't simply use my phone handset to return the call!

A Solution

What is needed is a mechanism where translations from @voipprovider.address to a dialling code can be standardised, and the numerical translation to be inserted into CLID numbers when calls are received.

Or at least that is what is needed at the handset end.

I'd like to be able to modify the code on the SPA3102 to enable a lookup table to be loaded. This lookup table would have a translation between the ascii addresses and numeric ones, for example:
If the number dialled were *1001999999999, the number would be translated to, and if a call were received from, it would be translated to *1002999999999 before being passed to the phone.

The lookup database could be standardised worldwide, however it is not essential, because the translation is done within the local modem.

The Stumbling Block

The stumbling block, as always, is access to the code! From the looks of the SPA3102, it contains GPL code, so I should be able to do the modification. My problem is that Cisco haven't released it (i.e. I believe there may be a GPL violation here).

On the CISCO website, you can request code, and you are advised that you will get a response within 2-3 business days. It's been 5 days so far, but I'm still hopeful - I've heard that they are quite responsive in this matter.

It's now 10 days, and I've submitted my third request. All that has happend so far is that Cisco appear to have added my email address to a junk mailing list, so at the moment, I'm not too happy.

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