Skype, SIP, VOIP, and the PSTN

[David Farber <dave () farber net>]

Begin forwarded message:

From:
Date: September 21, 2005 11:34:17 AM EDT
To: David Farber <dave () farber net>
Subject: Skype, SIP, VOIP, and the PSTN




            **********
**If you decide to post this on IP, please make it anonymous.
**I work closely with many SIP vendors and they may be sensitive
**to a view that is not completely optimistic.
            **********

A point was asserted on the IP list that Skype might be displaced by  
implementations based on the open protocol SIP.  Much as I might want  
that to be the case, as a practical matter I have substantial  
doubts.  My skepticism isn't based on mere theory - I sit here  
writing this from a box that is surrounded by SIP devices and I work  
with SIP implementations daily.

SIP is a protocol that is top-heavy and baroque.  It almost makes one  
yearn for the relative simplicity and elegance of ISO/OSI.

It's pretty easy to build a simple SIP device.  But there is a large  
distance between merely working and commercial quality SIP.  SIP  
implementors have a long and expensive road to follow to get really  
robust implementations.

But what is more important is this: SIP providers are going to burn a  
lot of operational cash every day isolating and fixing customer  
problems that arise out of the complexity of SIP.

Skype and other proprietary VOIP protocols could win over SIP because  
they may cost less to build and, more importantly, may cost less to  
operate.

Because of the potential operational cost overhead of SIP it is an  
open question whether SIP can be a viable contender in a VOIP  
marketplace in which customers expect to pay next to nothing and can  
instantly switch to another product based on an different protocol.

I doubt that users really care whether their phone call is set-up or  
carried using a proprietary protocol or not.

And there may be life yet in the PSTN.

VOIP may have the potential (largely undemnstrated to date) to to  
give better sound fidelity, but VOIP's end-to-end delay imposes  
considerable stress on human users who are trying to engage in a  
fruitful conversation. (VOIP should be avoided for dangerously  
stressful situations such as suicide hotlines.)

In addition the PSTN has been refined over decades so that its  
pathology is understood.  The PSTN is filled with mechanisms and  
tools to facilitate fast and inexpensive detection and repair of faults.


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