Skype Usage at Fermilab

About Skype

Skype (www.skype.com) is a free P2P (peer to peer) application that provides free voice-over-IP communication over the Internet. Use of Skype on systems attached to the Laboratory network is not prohibited per se. However, 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 at Fermilab), 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 user needs to reboot his system to stop the SuperNode call-routing activity.

Acting as a Skype SuperNode is considered a violation of the Fermilab acceptable use policy. Skype SuperNodes generate excessive amounts of non-mission 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 extended testing by 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 Fermilab network by implementing the following configuration on the user’s 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. Skype will require an Administrator right to be installed, but you should run it with a non-administrator account to prevent Skype from changing your Windows firewall rules.
  2. The user should configure his system such that Skype is not loaded at startup.
  3. A software firewall must be installed and enabled.
    • Windows XP firewall or Zone Alarm are examples of suitable firewalls for XP
  4. Exceptions for Skype must be disabled or deleted in the firewall setup. This is done using the Administrator account.
    • Windows XP Firewall: Settings>Control Panel>Windows Firewall>Exceptions

Detailed Configuration Instructions are located below under Instructions for Skype Configuration.

Using a non-Administrator account for Skype, the above firewall configuration should prevent the local system from becoming a SuperNode. A few additional caveats worth noting:

There is no technical support from the Network Section for either the Skype application or assistance in configuring the system to avoid becoming a SuperNode.

The user should read & understand the Skype End-User License Agreement, currently located at:

www.skype.com/company/legal/eula/

 

Instructions for Skype Configuration (Windows XP)


Guideline 2

The user should insure that Skype is not loaded at startup and is only running while the user is at the computer to receive or make calls. There are two ways to ensure that Skype does not 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 left. Continue to sign in normally.



Guideline 2 Cont.

Option 2: If Skype is already running you can disable it from starting when Windows starts by:

  1. On the toolbar in Skype go to Tools>Options.
  2. When the Options window appears click on the advanced tab on the left side at the bottom.
  3. At the top of the advanced screen under Startup uncheck the first box labeled "Start Skype when I start Windows"
  4. Continue by selecting Save at the bottom of the window.



Guideline 3

A software firewall such as Windows XP firewall or Zone Alarm must be installed and enabled.

To enable the Windows XP Firewall go to: Start > Control Panel > Security Center > Windows Firewall. The check box On (recommended) should be selected then press Ok.

 



Guideline 4

Exceptions for Skype must be disabled or deleted in the firewall setup. To disable exceptions for Skype go to: Start> Control Panel> Security Center> Windows Firewall> Exceptions. On the exceptions tab locate Skype, be sure that box for it is unchecked, and then press Ok to continue.