Aswath Weblog

Cloning of PSTN in VoIP Guise

Previously I have expressed my disappointment with the list of features touted by VoIP service providers. Today I read a story in US News that writes about new features facilated by VoIP technology. So I write about it once more.

The article quotes Gerry Campbell, a Time Warner Cable senior vice president. "The future growth of this business is through features, rather than price." He envisions “a wealth of applications developed by third parties, akin to software programs written for the pc.” This vision was stated many years back by Intelligent Network (yes the same IN that gave rise to the sarcastic “Stupid Network” moniker). But what is missing is the understanding why that vision more or less failed in PSTN. It might be true that "the telephone has been a closed shop, a closed arena." But that is not the whole story; there is a big technical point. The feature interaction problem is complex even when these multiple features are developed by a single organization and running on a single system. It is not clear how and why this problem can be solved simply because we are using IP.

Still, let us consider some of the exciting ideas the firms are touting:

• Single number for life – ITU has a standard for it that can be used in PSTN. With nationwide roaming, wireless service providers are offering this feature. 800 number service suggests that the technology is available.
• Central repository to collect all your voice and text messages – of course this has nothing to do with VoIP. A message server can collect the voice messages on the PSTN interface and then serve them on IP interface.
• Call forwarding to multiple numbers – By the way this feature is patented and is offered as a service by some operators for their PSTN subscribers. When SIP describes “forking”, the possible numbers include PSTN numbers. If SIP Proxy Server can do this, why can’t PSTN Server (SCP of IN)?
  
• Notification of voice mail messages via E-mail – again, why do we need VoIP for this. This is a capability of the voice mail server.
• Using your tv and remote control to make changes to your calling system – once more we are confusing back-end functions with actual interface.

So I am still skeptical of revolutionary features we are going to see from VoIP technology. So what are the benefits of VoIP technology?

• The startup cost for a new service provider is low (but that advantage disappears as it grows).
• End-user can communicate directly without the intervention of a service provider or can change the service provider at will with little impact.