Access Grid
From GridInfo
Contents |
What is the The Access Grid
The Access Grid is a set of resources that are used to support distributed collaborative interactions across the internet. The main framework is scalable videoconferencing, augmented by a number of presentation and application sharing tools. The Access Grid can be used for large-scale distributed meetings, smaller collaborative work sessions, seminars, lectures, tutorials, and training. The Access Grid thus differs from other tools that focus more on individual-to-individual communication, although it can be used in this mode.
The Access Grid's main development site is in the Futures Laboratory at Argonne National Laboratory.
Who could use the Access Grid?
The Access Grid is ideal for distributed groups who are engaged in any sort of collaboration. Traditionally such groups have used tools such as telephone and email to communicate. The Access Grid provides many new opportunities:
- It enables several collaborators to talk together in a virtual face-to-face environment
- By seeing each other, communication and interaction are easier than telephone conferences (and cheaper!)
- The Access Grid tool can be augmented by application sharing tools to enhance the interaction
- It is a low-cost alternative to holding face-to-face meetings (saving both the time and money costs of travelling)
Collaborations can use the Access Grid for regular or spontaneous meetings between partners in a collaboration.
The Access Grid is one of the technologies that will support collaborations working together as a virtual organisation, enhancing the value of collaboration.
Multicast technology
The Access Grid could clearly generate a lot of network traffic. In order to reduce the load on the network, the video and audio tools employed by the Access Grid (vic and rat respectively) use the multicast protocol for sending data across the internet. Multicast works by sending only one copy of the data (in this case, video and audio streams) even though there will be more than one eventual recipient. The idea of multicast is that separate copies of the data will only be created, as required, en route to the various recipients. By contrast, unicast is where the sender has to produce one copy of the data for each intended recipient.
The problem with using multicast is that often institution network components (switches and routers) and firewalls are set by default to not transmit multicast, even though these components may well have multicast capability. Although it is to be desired that institutes become multicast-enabled, in practice there is often the need to have a bridge between unicast and multicast communications. This means that a user without multicast capability can simply send one copy of the data to the bridge, and the bridge then send it onwards in multicast mode. The NIEeS runs bridges for the UK environmental sciences community, and the UK UK Access Grid Support Centre in Manchester runs a bridge for the wider UK scientific community.
Usage within suites
The headline usage is based on Access Grid suites, set up so that
- video is transmitted by more than one camera
- video is displayed on a wall using several projectors
- sound is recorded using several microphones
- sound is played within a suite using an amplifier and loudspeakers
- sound quality is maintained using echo cancellation hardware.
Personal/desktop Access Grid
It is also possible to use the Access Grid on standard desktops. The basic equipment is a simple webcam and audio headsets (microphone and earphones). In principle it is possible to use a simple table microphone or the computer's inbuilt microphone, and the computer's loudspeaker, but often this may result in other users hearing echoes of their own speech. If users find complete headsets to be intrusive, there are ways around this:
- use an external microphone (computer or table) and ear buds as in personal music systems
- use a directional boundary table microphone suitably positioned to avoid sound being picked up from the loudspeakers. These sort of microphones can be purchased quite cheaply (as low as £30)
- use a microphone that has built-in echo cancellation. These now sell for as low as £100 (click here for an example product sales site).
Interacting with the Access Grid
The paradigm used by the Access Grid is that of having virtual meeting rooms, called "virtual venues", and when you hold a meeting with some colleagues, you do so by entering a virtual meeting room. In principle, only people who are in the same virtual venue are able to send and receive video/audio streams to each other. The venue server will list all people who are in the same virtual venue as yourself.
Moving between venues means that you need to leave a venue and go into a "virtual lobby". From the lobby you will see all venues that can be accessed from the lobby.
It should be noted that the process of being in a virtual venue is not the same as being able to send and receive audio and video streams to people in the venue, although one wants to be able to do so. If there is a problem with audio and video, you will still be able to see that other people are in the venue.
Setting up the Access Grid on your desktop
- Setting up for Mac OS X
- Setting up for Microsoft Windows
- Setting up for linux
- Access Grid networking and firewall issues
- NIEeS bridges
Internal links
- Vic: the video tool
- Rat: the audio tool
- Multicast technology
- Virtual Organisation
External links
- Home page of the Access Grid project at Argonne National Laboratory
- AGCentral: a portal for the Access Grid community
- UK Access Grid Support Centre at the University of Manchester
- InSORS: a commercialisation of the Access Grid used by a number of UK Access Grid sites
