| Generic Services Technical Support Framework |
Generic Services (WP3) is currently represented as 'vertical' and is positioned alongside work-packages 4 to 9, and above work-package 2 (horizontal issues), but in some ways it is both a Service and a Service Provider. In terms of a Service Provider, it provides the necessary tools and utilities for each of the higher number work-packages, i.e., in the case of video-conferencing WP3 provides the knowledge base to make use of the standards defined by WP2. We have split the list of tools/utilities initially into the following categories:
Video-Conferencing
To make it easier for NetMeeting users to contact other NetMeeting users, we have installed an ILS (Internet Location Server) here at Manchester Computing (the G-MING HQ). When a user first installs the NetMeeting program it will prompt for the name of an ILS, which is usually a relatively heavily loaded system in the USA, by using our ILS system the user will get a listing of users quite a bit faster. For users wanting a higher bandwidth connection than NetMeeting is designed for, we use both ATM and ISDN networks for Video-Conferencing, which gives quite an increase in image quality, and is usually used for the type of meeting where one group in one location converses with one or more groups elsewhere in the world. It is recommended that the Generic Services group should help to co-ordinate the various Video Conferencing systems available to ensure that a common communication protocol exists. i.e., 'Will my NetMeeting work with LiveLan ?' and if so, which parts of each are compatible, such as the application sharing/collaboration features of NetMeeting. The G-MING Applications Program (GAP) have been evaluating various Video Conferencing packages, from the freely available NetMeeting program in conjunction with various Video Capture cards and Video Cameras. We have held a 'NetMedia' seminar at Manchester Computing to introduce the local academic community to some of the facilities available. Collaborative WorkingThis category of software develops the ideas from those of the Video Conferencing systems described above. A prime use of NetMeeting is its ability to share one or more applications in real-time without the need for either audio or video hardware. Users could for example collaborate to produce a PowerPoint presentation etc. NetMeeting could also be used in conjunction with a PowerPoint viewer to show the completed presentation to several other users almost anywhere on the Internet. Collaborative Working software builds on this type of usage giving further kinds of sophistication.
A new feature of BSCW is the ability to send an electronic mail message to the user whenever a workspace is changed, i.e., by the addition of new documents or modification of existing documents. In this way the user does not need to connect to the BSCW server just to see if there is anything new. BSCW can be used to arrange meetings, either physical face-to-face or to schedule a audio/video conference, and can also cause certain conferencing applications to start automatically at a predefined time. (NetMeeting, needless to say falls into this category) There are other collaborative applications available, and we will attempt to evaluate those as far as possible. Bulletin Board SystemsThere are Bulletin Board Systems (BBS) for almost any hardware platform or operating system, far too many to list here, but all of them have the ability for a user to login and examine messages and/or leave messages for other users.
BSCW allows the user to transfer different document types into and out of a workspace by making use of the MIME type for a document, so a Mac user can drop a Microsoft Word file into a workspace and a Windows95 or Unix user could then pick up the document without needing to know what package was used to create the document or needing to worry about Mac to Windows95 conversion details. An experienced BSCW user could override the MIME type if that is required. Although BSCW does provide these facilities one important consideration must be whether it can gain user acceptability when only simple bulletin board facilities are required. Proxy/Cache ServersA Proxy/Cache server is simply an intermediary system with a disk/memory cache. The proxy part can be thought of as a system which will fetch a document on the users behalf with the cache part as a temporary local copy of the document just in case another request is made for the same document. The vast majority of proxy/cache traffic is for WWW documents, but they can be used for FTP and Gopher documents just as easily. Some sections of the community may have specific requirements of a proxy/cache server, such as a way of filtering out any undesirable sites to schools or other bodies. It is possible to use a local proxy/cache to ensure that documents in a particular sphere of interest are rapidly accessible by using application specific proxy/cache. Streamed Audio/VideoThere are several methods available for streamed audio/video, of which we have been evaluating: RealEncoder/Server from Progressive Networks; NetShow Encoder/Server from Microsoft and the MediaBase Server/Player from Silicon Graphics, along with the Viewer software for Windows-95 and Linux for each (where possible). For medium to high bandwidth the MediaBase system offers the highest quality at the expense of hardware/software costs and the volume of data especially for such high quality pre-recorded streams.
For a sustained live video feed of reasonable quality we have found that a RealEncoder/Server combination would run on two systems separated by a fast Ethernet, as in the example of the live feed of the construction of the Manchester Mark-1 rebuild at Manchester Computing. In this case we have a Video camera connected to a capture card in a Pentium PC running Windows-NT Server and a copy of RealEncoder, which is sending a video stream to a HP/UX Unix system running the RealServer which makes the video stream available to a user by a single click on a link in a WWW page. Ideally this requires a dedicated dual processor system withncoder/Server combination. Pre-recorded video streams can be produced by either system and may be served using the relevant custom server or by a normal WWW server. Examples can be found in the references below. For Audio only streaming another very good example is the use of MPEG 1 Layer 3 audio files (MP3), of which there are many Encoders and Player utilities available for almost any platform etc.
References
This document is also available ZIP'ped up as an MS Word 7 document. |
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