IP Video Conferencing

IP based video conferencing is theoretically possible across any IP enabled network, be it the Internet, a Local Area Network (LAN) or Wide Area Network (WAN). There are many reasons why, in practice, video conferencing may not work including: the active baring of video conferencing protocols, the other traffic on the network or delays built up due to the signal having to pass through a large number of devices between users.
IP video conferencing is possible across the Internet but because there is no guarantee of capacity or bandwidth from one end of a link to the other, the results can be unpredictable. The problem is mostly the delay or ‘latency’ inherent in the way the Internet is structured. The Internet uses routing tables defined by the service providers that are optimised for data. Video and audio packets must arrive quickly and in sequence to deliver a video conference and the Internet has no way of doing this. This makes video conferencing across the Internet unsuitable for lessons where a teacher is working with a class and relying on the conference. Internet video
conferencing may be suitable for one-to-one personal links.
The advent of broadband networks between schools is beginning to make IP based conferencing more of a possibility. The greater capacity of a broadband network and the fact that many are privately managed networks can result in more predictable performance although other traffic may still be a problem. The network within a school could also be a bottleneck for video conferences. There will be no guarantee of performance for video conferencing until Quality of Service protocols are implemented on networks (see below). A managed broadband network is not the same as broadband Internet. The problem of ‘latency’with the Internet will still be present with broadband Internet access.
The network LAN within a school can also be used for conferencing just within the site. Many schools are now linked to regional networks such as the regional Grids for Learning - this potentially enables conferencing between schools, to LEAs and other connected institutions such as libraries or ICT centres. On a regional network where firewalls are used, video conferencing protocols have to be enabled to allow conferencing. The network managers may also have implemented a directory service to enable conferences to be established within and outside the grids (see below).
Calling between networks, e.g. from one regional network to another has to be enabled and supported by both networks. The capacity of the link between the networks also has to be considered. Security systems such as firewalls (security devices installed to protect a network)may restrict video conferencing. Some networks have established gatekeepers to control access, these enable users internal to a Grid or network to conference with external users without compromising the security of the network. Conferencing between networks can also be problematic due to the number of devices a call has to pass through, each potentially adding delay to the audio and video stream.