2007/02/22

Why should so much importance be placed on SIP? Mainly because it is the most widely accepted industry standard so most hardware/software vendors use it and practically all VoIP services use it.
This makes it very easy for almost anyone, anywhere to communicate with each other - usually very cheaply and often completely free. Please note that although it is naturally best to have a broadband connection for this it can be done effectively over a dial-up connection so long as you can accept reduced audio-quality. By the way, what SIP (session initiation protocol) does is essentially the setting-up of the calling-path, something akin to the dialling sequence part of a call on the normal telephone network.
After that both parties also need to be using the same methods of encoding and decoding the digital audio as they speak to each other. Again there are standards for this known as "codecs", and take note that certain companies have chosen to use proprietary codecs. Interestingly the two major names that apparently do not feel they need to follow accepted standards are those with the loudest sales/marketing voices - do I need to spell this out? Please write in if you do not know who they are!
There are many people who are using VoIP today, but are often using different service providers whether in the same country or different ones around the world. One of the beauties of using standards is that it can be made very easy to inter-connect between these service-providers ( sometimes called ITSP's for Internet Telephony Service Providers, or VSP for Voice Service Providers). Some amazing work has been done by an outfit called SIP Broker
who are co-ordinating a huge list of access-codes that are used to allow users to call contacts on other networks. It already numbers some 500 codes, mostly 3-digits but later additions are 4.
Let me give you an example - If you are a subscriber with Packet-8 in the USA and have the account number 12345 and have a friend in Europe on say, Sipgate, then they can call you by dialling this sequence: *449-12345. Brilliantly simple isn't it!
Now although there are already some very cheap rates for calling between the USA and Europe using this SIP method is entirely free!
ITSP's have to pay the telephone companies to terminate calls on the public switched telephone networks (PSTN) but most of them have agreed to accept each other's SIP calls free-of-charge since there are no additional costs to them anyway. Very public-spirited wouldn't you agree?