Guidelines for Using Skype

The following guidelines are recommended for Skype installations:

  1. If possible, install Skype on a PC sitting behind a UDP-restricted NAT (Network Address Translation) device. That means the NAT device will do PAT (port address translation or port mapping), thereby all incoming UDP connections will be disabled. By doing so the Skype client cannot be turned into a Supernode and therefore it will not share the University’s network resources with other Skype clients.
  2. Only launch the application when it is necessary to make an outgoing call or when an incoming call is expected so that network resources will not be unnecessarily engaged.
  3. Keep all the calls to a reasonable length to reduce the network resources consumed by Skype.
  4. Turn the application off (closing the Skype application and turning off its background process) when not in use. Restarting the background process at regular intervals (e.g. once per hour) will reset the number of IP connections and prevent it from growing to an unacceptable level.
  5. Register with the CSC for Skype installation in NCMS (type `Skype’ in the field ` Communication protocols used other than standard IP’) so that we can assess the potential impact of Skype.

Whoever running Skype must help control the number of concurrent IP connections created by the application. (Note: you can verify the number session opened by the Skype using 'netstat-an'' in the Command Prompt [from Start®All Programs®Accessories®Command Prompt]). The CSC will block the network connection of a Skype client without advance notice when the number of IP connections becomes excessive (e.g. over 1,000) or when the network performance begins deteriorating.

csc@cityu.edu.hk