Video Conferencing Systems > 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.

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.



Quality of Service (QoS)

A series of Quality of Service protocols has been established which can be implemented on a network so that certain applications such as video conferencing that require dedicated and predictable bandwidth can ensure the bandwidth is available for the duration of the conference. The bandwidth will not be affected by the activities of other users. Quality of Service may be implemented on a LAN or a regional network.



Establishing IP Based Video Conferences

Each device on a network has an address called an IP address (for example 211.104.141.10).

At its simplest, a conference call may be established by calling the remote user’s IP address. Many computer-based systems will use software, such as Microsoft NetMeeting or CUseeMe, to establish the call. Other computer-based systems use proprietary software. Using the IP address works as long as you can find the address of the remote user; however, these addresses are often allocated to a system when it is switched on or connected. This means that a particular system may pick up a different address each time it is used. This is often the case with systems connected to the Internet. Addresses may also be unavailable for security reasons.

The solution is to use some form of directory. Many networks have directory servers for conferencing; there are also some global directories. Each system logs onto the directory server when it is started up. A list of those logged on can then be seen as a list of names. A conference is established by clicking on the name of the remote user; the system then takes care of addressing issues. Software such as Microsoft NetMeeting has an option to add directory server details. Access to an ILS or Internet Locator Service is required to use this facility.

Some networks have set up a gatekeeper. Gatekeepers operate in a similar way to directory servers but can also allow conferences with external users without compromising the security of the network. The details for a particular network should be obtained from the network administrator.

Services are available that handle directory functions and enable advanced scheduling of conferences, multipoint conferences and bridging between different systems such as IP and ISDN.



ISDN to IP ‘Bridging’

Because the two systems use different protocols a ‘bridge’ between the two is required to conference between ISDN and IP. This equipment would normally be part of a regional or national network. Some companies provide bridging as a chargeable service. A limited number of video conferencing units can bridge within the unit.