If you run Skype outside of a NAT configuration, you may be passing traffic as a supernode. Skype’s documentation claims the impact of this extra traffic is negligible, but you can prevent your Skype client / connection from becoming a supernode altogether:
- Beginning with Skype 3.0, an explicit switch is provided in the registry settings to allow the disabling of supernode functionality.
- Any computer hosted on a network that is behind a network address translation (NAT) device or restrictive firewall will disable supernode functionality.
- Skype clients behind an HTTP or SOCKS5 proxy will not serve as supernodes.
I’m guessing that most of you are behind a router with NAT, but the University of Waterloo has a fantastic wiki page with further Skype tweaks in relation to the supernode feature.