Comments on: How Does Skype Work? [Technology Explained]

By: Sean Zicari

Sean Zicari — Thu, 14 Jan 2010 15:26:56 +0000

Greetings. I enjoyed the technical overview that this articles provides. I have to say that I’m genuinely surprised at the quality and low latency of calls made through Skype. I was offering tech support to an individual, trying to get his microphone set up and ready for use with Skype. I was on the phone with him and on a Skype call with him, and once we finally got his microphone working I found that the timing between the phone and Skype was identical. Skype’s call quality was easily as good, too.

A day or so later, I was on a call with my business partner – we were both on cell phones. We switched over to Skype and found that our cell phones were delayed about .5 – 1 second, whereas the Skype call had the speed and quality of a land line phone. Needless to say, Skype is an impressive use of VOIP and P2P technologies.

By: Lexi Wright

Lexi Wright — Mon, 24 Aug 2009 21:14:22 +0000

I agree with Guy that VoIP systems continue to get better and better. The main problems of connection, tracking capabilities with 911 and privacy still stand, but are far less than what they used to be.

By: Stefan Neagu

Stefan Neagu — Fri, 31 Jul 2009 05:52:49 +0000

All good points. Thanks for your comment and vigilanc, Franchu.

By: Stefan Neagu

Stefan Neagu — Fri, 31 Jul 2009 05:32:28 +0000

Yes, for the sake of simplicity I bundled Skype together with standard SIP VOIP services. But Skype has a directive to first try and establish a direct connection, and only users behind NAT are connected through supernodes. I don’t believe speed is improved by routing packets through multiple hops, if anything, it decreases the reliability. I believe Skype doesn’t use P2P for increasing speed.

By: Guy McDowell

Guy McDowell — Fri, 31 Jul 2009 04:11:38 +0000

I like the article. By explaining that the call is broken into packets, I think more people will understand the inherent problems with VoIP. It’s still a great technology, and really in it’s infancy.

Another problem with VoIP is that 911 dispatchers can’t trace the call in case of emergency. Hopefully you have registered your home address with your VoIP provider, so 911 can find you if you go down before you can give an address.

Expect VoIP to grow and get better though. Just my opinion.

By: Jack Cola

Jack Cola — Thu, 30 Jul 2009 23:59:38 +0000

As JadoJodo mentioned, Skype uses the Peer-to-Peer network. Skype was originally going to be called Sky peer-to-peer, then shortened to Skyper, then the dropped the R due to domain names being taken.
http://en.wikipedia.org/wiki/Skype

By: Franchu

Franchu — Thu, 30 Jul 2009 21:18:24 +0000

Some extra precisions from my side…

SIP is not comparable to TCP/IP… actually SIP still uses quite often TCP/IP being an application layer protocol. Please check the Internet protocol suite tower http://en.wikipedia.org/wiki/Internet_Protocol_Suite or the OSI protocol layers structure.

VoIP refers exclusively to voice communications, and hence the name http://en.wikipedia.org/wiki/Voice_over_Internet_Protocol

SIP is only an initiation and session control protocol, for the actual audio/video streaming you use another protocol (usually something along the lines of RTP http://en.wikipedia.org/wiki/Real-time_Transport_Protocol ). And those RTP packets are sent over UDP, as a missed packet doesnÂ´t make much of a difference.

As a final comment, I would like to say that even if the article is explained in layman terms which is very good for reaching a wide audience, it is always good to remain technically correct :)

By: Adam

Adam — Thu, 30 Jul 2009 20:22:30 +0000

For the love of [your diety here], don’t get involved with Vonage if you ever think you might want to get out of it at some point. They make it hard if not impossible; their “retention” department is all about saying no to your cancel request, over and over again. Happily keeping your money all the while, too.

By: JadoJodo

JadoJodo — Thu, 30 Jul 2009 14:22:27 +0000

This article, while a good guide to standard VoiP, incorrectly identifies Skype as a standard VoiP-via-SIP technology. While the general idea is the same, data is broken down into packets, the technology is not. Skype is based on the P2P framework, the same as those found in KaZaA, LimeWire, uTorrent, or any other P2P file-sharing program. This is what is so unique about Skype. While other VoiP providers must make-do with connection speed limitations, Skype is using the P2P network of its users to increase quality. This can be read about here.