I received a lot of communication since my last blog posting in which I explained how the Skype client can start behaving as a supernode and using your bandwidth to facilitate communications between other Skype users. Several people thanked me for bringing this information to their attention while others pointed out some of the other issues that Skype throws up for both consumer PC users and business IT Managers. So I thought it might be helpful to offer this follow-up posting.
First up, it is possible to change Skype's default behaviour to prevent it becoming a supernode. As the Ja.net report explains "placing Skype behind a default deny firewall prevented supernode behaviour while still allowing calls to be made and received using web protocols." If you're worried about your bandwidth being used by Skype to facilitate other calls you simply need to use and configure a firewall that will prevent this supernode behaviour. There's a lot of debate about this on the Skype Forums. Check out these pages for a taster.
If meddling with firewalls and deny lists sounds a little above your head, but you still want to use Skype, then you have little choice but to accept that your Skype client could become a supernode. You best option to prevent this behaviour is to only run the Skype application when you wish to make or receive calls. Changing the option that allows Skype to start up when your computer starts is a smart first step.
If you're sufficiently techno-savvy you could also install a software application like NetLimiter or Net-Peeker that prevents Skype from using excessive bandwidth.
Another correspondent asked why Skype was allowed to use their bandwidth without their permission. The problem here is simply that anyone who has installed Skype has already given their permission to Skype to use their bandwidth and processor to facilitate communication between Skype Software users. Don't believe me? See Article 4.1 of the Skype EULA (End User Licence Agreement) that you are required to accept before installing and using Skype. The moral of the story is to always read the details of any EULA that you are required to accept. As one correspondent wrote to me "there's no such thing as a free lunch". If something looks too good be true, it probably isn't.
Skype has issued assurances that the bandwidth load from being a supernode will never exceed 5kb/second. If used continuously in this way that adds up to around 1.5GB a month. If you think you qualify as a potential supernode and have a capped or pay as you go DSL connection to the internet you should decide if this 1.5GB load is affordable and acceptable for you.
Finally, if you'd like to know how Windows Live Messenger differs from Skype, my colleague Mark Deakin has posted some interesting advice on his blog.