Collaboration between institutions based in different cities, countries or continents is becoming the norm in both commercial and academic worlds. The ability to attend meetings and interact with people effectively without incurring all the negative implications associated with travel - such as cost, expense, environmental impact and reduction in productivity - is a truly worthwhile goal. Access Grid  was invented by the Futures Group within Argonne National Laboratory  in 1998 as a response to perceived weaknesses of traditional videoconferencing in handling group-to-group collaboration between large numbers of sites and its lack of emphasis on advanced data sharing. Access Grid takes the concept of collaboration further than merely sharing voice and video into what is termed as an Advanced Collaboration Environment.
The Access Grid is based upon the metaphor of virtual venues. Just as one can meet other people in physical rooms and interact with objects in that room, virtual venues are places in which participants can see and hear each other. They are also places in which virtual objects can be left, such as data, applications or services.
The original intention of the Access Grid was to do for humans what the Grid  does for machines. Recent releases of research software, known as 'Access Grid 2' , have focussed more on integrating core Grid technology, utilising X.509 certificates for security and looking more at the integration of applications and services to support 'virtual organisations', such as groups of biologists or physicists who work across institutional boundaries.
Access Grid has attempted to prioritise human factors issues. A typical Access Grid node has a large display: often a whole wall is used to show three projector images side by side. A large pixel-space is necessary for three reasons: so that video streams of each of the potentially huge number of sites taking part is displayed; to display data sharing tools that are increasingly a component of complex collaborations; and to show life-size images of participants so that facial expressions and body language ('non-verbal cues') may be seen. Gaining maximum benefit from non-verbal cues is also the reasoning behind having multiple cameras - many nodes have three or four positioned strategically around the room. This enables a single camera to be devoted to as few participants as possible - preferably one camera per person - to allow a newsreader-type head-and-shoulders shot.
The audio in Access Grid is currently a single, mono stream, although there is research looking to enhance this to stereo or even to enable 'sound localisation', where the sound appears to come from different parts of the room. However, in any videoconferencing or collaboration environment, it is vital that the audio is of excellent quality. Any imperfection, such as buzzes or hiss, will detract from the effectiveness of the meeting as participants will be unable to concentrate on what people say. Poor quality audio is also hard work and it can be very tiring to take part in such a meeting. Therefore, a major element in the cost of an Access Grid node is on the purchase of top quality audio equipment, such as speakers, microphones and - vitally - an echo canceller, which prevents sound from one site being fed back to that site through another's microphones.
The sharing of data within the Access Grid, including video and audio streams, is performed over the Internet and there is no technological limit to the number of sites that may participate. For example, a recent conference held using Access Grid technology, SC Global 2004 , had sessions involving up to 50 sites from all around the globe. With this many sites interacting, each sending multiple video and audio streams to every other participant, efficient use of network bandwidth is vital. This is achieved using a peer-to-peer architecture (i.e. no central server distributes data between participants: they each send to each other), implemented by using multicast networking .
Multicast differs from unicast, or conventional networking, by the fact that each sender only transmits one copy of the data, no matter how many recipients are involved. Network routers between sender and receiver determine when copies need to be made to ensure correct delivery. This means huge savings in the amount of bandwidth - and processing power - that is required for large, multi-site meetings.
However, multicast is not yet ubiquitous: new academic sites which are installing Access Grid may start out with no multicast provision because the default is not to enable it; multicast is not supported by commercial Internet Service Providers (ISPs); multicast may go 'down' upon upgrades to router software (although this problem is becoming less frequent); and there are often multicast connectivity problems internationally. Therefore, for the foreseeable future, there remains a requirement for multicast-unicast bridges that reflect packets to and from unicast-only sites.
In April 2004, the Access Grid Support Centre (AGSC)  was established at the University of Manchester to provide support for UK academic Access Grid sites, including the provision of such multicast-unicast bridges. Funded by the Joint Information Systems Committee (JISC)  and managed by UKERNA , its aim is to improve the Access Grid experience through training, support, Quality Assurance (QA) tests and the provision of a number of services.
In-depth training consists of a series of courses, which cover issues from introductions to Access Grid through to debugging and fault-finding techniques. QA tests improve the quality of facilities by checking audio, video and network quality at remote nodes, as well as the use of shared presentation software and Jabber  - messaging software used for sideband conversations between participants or technicians.
A virtual venue server supports UK-only venues in addition to the standard venues. A number of multicast-unicast bridge services are provided for users of commercial and research software and also to assist users who may wish to connect with low-bandwidth capability, such as broadband at home. For the first time for many UK sites, the AGSC runs a service that allows the presentation of Microsoft PowerPoint™ over a Web browser without the need to distribute slides beforehand. Also available is a facility to record meetings.
It is anticipated that in the coming years, collaborative tools will come to be developed that enhance, or that can be used alongside, the Access Grid. The AGSC is likely to be a major player in ensuring that these tools are rolled out so that users of Access Grid facilities can extract maximum benefit from them. The aim of the AGSC is to help the UK to realise fully the potential of Access Grid as a tool for highly effective remote collaboration.
Although users of Access Grid are enthusiastic, there remain hurdles to a dominance of this technology over alternatives. Perhaps the most significant is the inability of Access Grid to interoperate with more conventional videoconferencing. H.323/H.320 systems are very widespread, particularly in industry, and the requirement to have Access Grid technology at each endpoint may be a barrier to further expansion. There have been attempts to implement interoperability between the systems, most notably by inSORS Integrated Communications Inc., a commercial provider of an Access Grid-like product, but there remain problems because of inherent differences between the technologies, such as inconsistencies in the way in which they handle large numbers of multiple sites .
There are also profound problems with robustness, ease of installation and maintenance associated with recent releases of the Access Grid research software and there are signs of frustration among the user community . The future of the Access Grid concept may well lie in a commercialised version of the product that concentrates on robustness and ease of use. The aforementioned inSORS offers a solution that interoperates almost seamlessly with Access Grid. However, there is also research currently being undertaken by a certain major software company into a product that borrows many features of the Access Grid, which is known as ConferenceXP .
Whatever the future of Access Grid, there is a pressing need to implement usable and effective alternatives to travel, which, if undertaken to excess, will have increasing and serious negative consequences in terms of the productivity (not to mention the sanity!) of the frequent travellers among us, as well as adding immense pressure to the environment, which many believe is already showing worrying signs of strain through global warming. The Access Grid, whilst it may not be the ultimate solution, has helped to show us glimpses of the direction in which we might be heading.