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Internet Telephony

1. Introduction

Internet Telephony or Voice-over-IP (VoIP) is an increasingly popular way of making phone-calls via the internet instead of using the conventional telephone system. This document gives a brief introduction to the use of VoIP on the Oxford University's network.

VoIP calls can provide additional facilities (such as video) compared to conventional phones, and can give much cheaper call costs - calls can even be effectively free if you already have access to an internet connection.

The participants in a VoIP call can be:

  • A computer fitted with suitable audio hardware (e.g. microphone, speakers/headphone) and running VoIP software
  • A dedicated VoIP handset (or conventional handset connected through a VoIP adapter)
  • A conventional (non-IP) telephone handset (only as the recipient of a call).

For computer-to-computer calls, a number of free options are possible. VoIP calls to conventional lines are likely to require use of a commercial VoIP service.

2. VoIP Restrictions on the University Network

University regulations regarding peer-to-peer technology have been revised (18 June 2010). The University IT regulations now state:

"Use of file-sharing technology and participation in distributed file-sharing networks may be subject to additional regulation and restriction in order to prevent excessive use of university network resources, or the use of those resources for purposes unconnected with the University. If a user has any reason to suppose that an application employs peer-to-peer (p2p) or other file-sharing technology, they should seek the advice of the IT officer responsible for the college or departmental network on which they propose to use the software."

However, this does not mean that you can use any peer-to-peer application regardless. The use of peer-to-peer software/services may be restricted by local policies within individual colleges and departments. Some colleges and departments may operate a relatively lax policy, others may be extremely restrictive. Different policies may apply to wired and wireless networks owing to the differing bandwidth available. Local policy may forbid certain software or network usage irrespective of whether it uses peer-to-peer technology; You should check your own unit's policy in this area before using any peer-to-peer product or service.

This document cannot describe policies within individual units. It is each user's responsibility to ensure that they comply with any local regulations as well as University-wide rules; in the event of any queries they should ask their local IT staff.

The ICT rules regarding peer-to-peer technology are on the ICT web site.

The next few sections list some VoIP products and services whose use is currently permitted on the Oxford University network.

3. Skype

Skype ( is a popular VoIP software product that allows users to make free VoIP calls to other Skype users. The University requires that anyone using Skype on the Oxford network should configure the software as specified in the installation and configuration instructions.

The main reason for the special configuration requirements is that Skype can use excessive network resources in certain cases. This is because a machine running Skype can, without your knowledge or control, act as a 'Supernode' exchange for routing calls between other Skype users. The required measures given in the setup instructions are designed to reduce this possibility.

IT Services has no particular expertise in use or trouble-shooting of Skype. The configuration pages provided are purely to avoid the program overloading the Oxford network. Skype have an FAQ and Support page which covers most common problems.

4. VoIP Between Two Computers

A number of software products exist which allow the making of Internet phone-calls between two computers. Some examples are listed below - note that inclusion in this list does not imply any official recommendation or endorsement whatsoever by Oxford University. IT Services reserves the right at any time to disallow the use of any product that is deemed to infringe the restrictions on P2P resource-sharing.

  • Windows Live Messenger (formerly MSN Messenger) - Free PC-to-PC phone/video for Windows and Mac users
  • Yahoo Messenger - Free PC-to-PC phone/video for Windows users
  • Google Talk - Free PC-to-PC phone for Windows users (Still in beta-test and requires a Gmail account)
  • iChat Free Mac-to-Mac phone/video/conferencing for OSX users

5. Calls to Conventional Land-lines and Cell-phones

To communicate from a PC or VoIP handset to a conventional (non-IP or PSTN) phone, you will need to subscribe to a commercial service that provides this facility. Some examples are listed below - note that inclusion in this list does not imply any official recommendation or endorsement whatsoever by Oxford University.

  • BT Communicator - call convential phones from your PC
  • BT Broadband Talk - make VoIP calls via an ordinary handset plugged into your own broadband connection
  • Vonage - call conventional phones from your PC or Mac

Some of the products in the previous section can also be extended (at a charge) to make or receive calls to/from conventional phones.


Written by IT Services. Latest revision 13 December 2017