You probably have an idea by now how I don’t like Skype, well today I’ll go into some of the details as to why I don’t like it.

Skype is a peer to peer application and under some circumstances, the Skype client uses the specified bandwidth of between 24 and 128KbPS. If you have a high speed internet connection and your firewall is not very restrictive, your PC with Skype might become a “supernode”. In this mode, Skype starts to relay signaling for other Skype users that are behind NAT (network address translation).

You can test this behavior. Run a packet capture on your network before installing Skype, then capture packets after installing Skype. You’ll notice that if you are directly on a publicly routable IP address, your machine starts using a lot (if not all) of your available bandwidth. You’ll notice traffic going out to all sorts of addresses around the globe.

The bandwidth usage can be so considerable that in certain circumstances it has brought down Linksys routers (typically used as residential gateways).

Skype uses both TCP and UDP ports for this traffic and in tests can use up all bandwidth in a 100MbPS connection. Now think about multiple users running Skype (not even using it) at the same time.

So until Skype starts to ship with some sort of a management tool to enterprise to limit this “supernode” mode, I will not recommend anyone use Skype, besides it’s not like it’s free. Why would you want to use Skype when you can use other VoIP services for free!

There is no such thing as free VoIP calls if you intend to call regular telephone lines. Some services come close and if you are ok with calling other computers only there are some free services.

Most services that tout to be free when calling land-lines, in fact require a deposit or have trial period limitations. Some services give you certain amount of time free, and then start charging when you exceed the threshold, so pay attention to how much time you are using with such services.

If you are only calling another computer, then why even bother with services such as Skype and their Suprenode issues? Simply use Google Talk or MSN/Windows Messenger! Google Talk has a nice web interface not requiring software installation on your machine, great way to VoIP enable any PC.