What is Skype?

Skype is a program that provides a way for users to make telephone calls over the Internet. Skype is compatible with most Operating Systems and an ever growing list of physical devices including specific cell phones. See www.skype.com for more specifics on compatibility and the latest features. Skype can also be used as a simple Instant Messenger device much like AOL IM, Windows Live, and Yahoo.

How to Get Started

Download Skype at www.skype.com and follow the instructions on the download page. After you’ve installed the software launch the application.
When you launch Skype a window will pop up that asks for you to create a Skype account:
Follow the instructions and after you create the account you can log in like any other instant messenger service via the welcome screen:

Problems with Firewalls

Default firewall settings normally allow Skype to run with no problems. In cases where there are custom firewall settings that prevent Skype from running normally, returning the firewall settings to default is the best option. Normally, when Skype restarts, it will automatically re-enable its firewall exception.

Supernode Problems on Campus

Supernode is a term used to describe the handling of data flow and connections for other users in a peer-to-peer (P2P) setting. This feature generally requires additional network bandwidth and CPU time. In Skype, a supernode is used to maintain information of users who are online at a given time.

A simple VoIP call using Skype uses between 24 and 128kbit/s. When a computer using Skype is running as a supernode, bandwidth usage nearly doubles. When a large number of users on the same network function as supernodes, considerable bandwidth is consumed by users outside of the UNC network. This significant use of bandwidth can drastically lower a community’s network strength and thereby slow down all internet connections. In addition to bandwidth use, computers running as supernodes let Skype open network connections over TCP (Transmission Control Protocol). TCP connections can number over 1500 at a time. Certain routers start running into problems with such a large number of TCP connections being open simultaneously.

Note: Configuring your computer as a Supernode can be a violation of the Networking Acceptable Use Policy.

Prevention

You can prevent your computer from acting as a supernode in one of three different ways:

Changing access to port 80 and 443:
- Launch Skype > Tools > Options > Advanced > Connection
- Uncheck the box marked “Use port 80 and 443 as alternatives for incoming connections.”
- Click “Save”.
Beginning with Skype 3.0, the supernode feature can be turned off with a switch provided in the registry settings.

Warning: Editing the registry can cause problems with your computer. Only follow these instructions if you are comfortable working with advanced settings and configurations.
- In Windows open your Start Menu and type Regedit
- Then navigate to HKEY_LOCAL_MACHINE à SOFTWARE à SKYPE à PHONE
- Go to Edit >New > DWORD Value
- Type in “DisableSupernode” for the name.
- Right click on “DisableSupernode” and click “Modify”. Enter 1 for the value data and click OK.
Any computer hosted on a network that is behind a network address translation (NAT) device or restrictive firewall will automatically disable the supernode feature.