SkypeOut voice quality - Part 1

Tony Austin
Monday, 03 September 2007 09:52

Opinion and Analysis

Skype PC-to-PC voice clarity has generally been regarded as pretty good, often crystal clear. But it isn't always, and Version 3.2 saw important improvements. However, the voice quality of SkypeOut calls remains contentious, and seems especially dependent on where you're calling from as well as where you're calling to. This first article on Skype's voice quality examines several general considerations, with subsequent articles delving a bit deeper into particular aspects of them.

I'm deep into researching a number of topics for discussion on ITWire. This has been taking me longer than expected, since some organizations don't make it at all easy to "open the kimono" and get to the real facts behind their product and services.

One that is close to my heart, as a long-time and still keen Skype user, is the matter of QoS (Quality of Service) including reliability and voice clarity. In this case, I'm hoping to get feedback from Skype themselves, not the consumer support desk but from a Skype executive/architect or two with in-depth knowledge.

I first started using Skype back in its Beta testing days during late 2003 and early 2004. Even back then, given a reasonably fast broadband connection (such as the Optus Cable that I've been using all along), the voice quality for PC-to-PC calls was impressive. Surprisingly, over slow dial-up connections the quality was often also quite tolerable, much better than what I recall of the Voice over Internet Protocol (VoIP) attempts in the mid-to-late-1990s, when the likes of companies such as Net2Phone came and went.

For PC-based calls, the Skype peer-to-peer (P2P) architecture generally works quite well -- most of the time. The spectacular mid-August 2007 failure just proves that there's always a distinction to be made between architecture and implementation: see Skype users don't disconnect your PSTN service just yet and "Perfect storm" sank Skype. (Presumably they've now tweaked the network self-healing parameters to cope with future storms of this kind.)

You can gain some insights into the architecture in the September 2004 paper by Salman A. Baset and Henning Schulzrinne of the Department of Computer Science at Columbia University, New York: " An Analysis of the Skype Peer-to-Peer Internet Telephony Protocol" and from the official Skype Guide for Network Administrators.