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What is Skype?

Skype is a free Internet telephony product that uses peer-to-peer (P2P) networking protocols. It effectively allows users to make free internet-based phone calls between one Skype user and another by Voice Over Internet Protocol (VOIP). Users can also purchase 'Skype-out' credit to allow calls to be routed to standard Public Service Telephony Network (PSTN) lines.

IT Services will allow the use of Skype on the University network and on the Roaming  (Wireless and Wired) network only if it is installed with setting so that it does not start automatically or use the university network as a supernode. For instructions, see the faq at: sussex.ac.uk/its/help/faq1478

The reason for installing Skype with these settings are:

The main reason is its very aggressive use of network bandwidth. For Skype to work it has to set up peerings with other Skype nodes. It does this when a user logs on and joins the network. A critical part of the skype network is what are called supernodes. Because Skype has no central exchange it has to dynamically allocate switching nodes from the users that are currently logged on. It has various methods of doing this but if a node is designated a supernode lots of traffic will get routed through it. For various reasons hosts on the University network are prime candidates for being designated supernodes and can end up routing a lot of traffic on behalf of people who have nothing to do with the University.

If you use Skype, without our settings, you may be contravening the Janet acceptable use policy. Your network connection will stop working or work very slowly.

For information on why this is see the faq at: sussex.ac.uk/its/help/faq1217

Skype and the Janet Acceptable Use Policy

Access is provided to the internet via Janet, the high speed education and research network. Two sections of the Janet Acceptable Use Policy may apply to Skype. Section 19 of the Policy prohibits "deliberate activities with any of the following characteristics:

• wasting staff effort or networked resources, including time on end systems accessible via Janet and the effort of staff involved in the support of those systems;
• using Janet in a way that denies service to other users (for example, deliberate or reckless overloading of access links or of switching equipment)"

Section 24 of the Policy prohibits "provid[ing] access to Janet to third parties without the prior agreement of Janet (UK)", but Sections 22 and 23 permit a limited amount of such use provided this is regulated by the customer organisation.

Uncontrolled use of Skype, and particularly its bandwidth-hungry super-node behaviour, is likely to breach one or both of these sections.