Document last modified on Sunday, October 01, 2006

About Skype

Skype is a free P2P (peer to peer) application that provides free voice-over-IP communication over the Internet. Although the Office of Information Technology accepts Skype as a beneficial, even vital tool for some of our users, the use of Skype in its default configuration can be harmful to our network.  Skype calls are routed across the Skype network through other Skype systems, called SuperNodes. Any system running the Skype application runs the risk of surreptitiously being elevated to the status of SuperNode. Computers with a fast connection to Internet (such as those at ETSU), combined with high speed CPU, are most likely to become SuperNodes. A SuperNode can generate a considerable amount of traffic by opening a large number of concurrent connections for off-site systems, even after the local user has discontinued using the Skype application on his system. Generally, the SuperNode call-routing activity will persist until the computer has been restarted.

Acting as a Skype SuperNode is considered a violation of the OIT acceptable use policy. Skype SuperNodes generate excessive amounts of non-relevant traffic and raise potential public embarrassment concerns regarding inappropriate use of government-funded resources. Local systems that become Skype SuperNodes routinely get blocked from off-site access by an automated blocking utility, resulting in denial of off-site access for the end user. The blocks are automatically dropped when the SuperNode activity stops, but are reinstated if the activity resumes.

Based on research borrowed from the Fermilab Networking Section, a procedure has been developed to configure systems to run the Skype application, without becoming a SuperNode. The testing has been conducted on a Windows XP system; however, the general approach and configuration settings should be applicable to other platforms & operating systems. These procedures work with the current release of Skype. There is no guarantee these procedures will function properly in future releases.

Based on this general information and the guidelines below, Skype can be installed and used on the ETSU network by implementing the following configuration on your system:

Skype Guidelines

1. For Windows XP, Skype version 2.0.0.97 or greater should be installed. For Linux or MacOS, the most current version of Skype should be used.
2. Skype should be configured not to load as the computer starts up. (see details below)
3. A software firewall must be installed and enabled.
   • Windows XP Service Pack 2 includes a sufficient firewall, accessible via Control Panel.  (see details below)
4. Exceptions for Skype must be disabled or deleted in the firewall setup.
   • Windows XP Firewall: Start Menu -> Control Panel -> Windows Firewall -> Exceptions  (see details below)

Detailed Configuration Instructions are located below under Instructions for Skype Configuration.  This configuration should prevent the local system from becoming a SuperNode.  Please be advised that OIT can neither offer technical support for the Skype application, nor can we assist in configuring the system to avoid becoming a SuperNode.  Please read and understand the Skype End-User License Agreement.

Instructions for Skype Configuration (Windows XP)

Guideline 2

Please ensure that Skype is not loaded at startup and is only running while you are at the computer to make or receive calls. There are two ways to configure Skype not to start when Windows starts.

Option 1: On the Sign-In window in Skype, uncheck the box labeled "Start Skype when the computer starts" as shown in the image to the right. Continue to sign in normally.
Option 2: If Skype is already running, you can disable it from starting with Windows by following these steps: On the toolbar in Skype, go to Tools -> Options. When the Options window appears, click "Advanced" in the lower left. At the top of the Advanced options page, uncheck the first box, labeled "Start Skype when I start Windows." Hit the Save button at the bottom to apply the change.
Back to guidelines Guideline 3
Windows Firewall or another software firewall must be installed and enabled. To enable the Windows XP Firewall, go to the Start menu -> Control Panel.  If Control Panel appears in Category View, switch to Classic View using the link in the left window pane.  Double-click "Windows Firewall."  Make sure the radio button next to "On" is active. Click OK to apply any changes and close the window, or click the "Exceptions" tab to continue with Guideline 4.
Back to guidelines Guideline 4
Exceptions for Skype must be disabled or deleted in the firewall setup.  If you are using Windows XP's Firewall, open the firewall configuration the same way you did in Guideline 3.  In the firewall configuration window, click the "Exceptions" tab.  In the Programs and Services list, locate Skype.  Uncheck the box next to it, and hit OK to save any changes.