Individuals, community organisations and small businesses need a low cost access, and may find that they use more than one service provider. This requirement can be met by providing dial-up analogue phone lines, connected to modems, typically running at a bit rate of 19.2 kbps. Use of a Web client such as Mosaic is possible over these connections, but the increasing multimedia content of Web pages means that retrieval of a 20 kbyte image could take 8 seconds. The basic problem for remote Web users is that the resources on the Internet and the Web HTTP protocol were initially intended for use on permanently connected local and wide area networks where typical bit rates are up to 10 Mbps, connection is fast, and often appears as a free service to the user. Users of these networks typically start feeling frustrated if nothing appears on their screens after 2 seconds.
In contrast the remote community user pays for access and phone time, and sees an inferior performance. While work may be under way to extend the HTTP protocol to improve the use of available bandwidth [HREF 3], the basic problem of too much information and too little bandwidth remains. Of course it is possible to disable image display in Mosaic client, or subscribe to a text only Lynx browser service in order to reduce the information which has to be retrieved. A Lynx browser service has been available for some time from the Manchester HOST but users do demand the ability to view images. Multimedia applications of Web technology are being developed such as tourism databases, public points of information, where images are an integral part of the presentation.
ISDN (Integrated Services Digital Network) telephone
connections can help to provide the sort of high speed, dial-up
connection that community users require. ISDN lines run at up to
64 kbps per channel, without compression and are typically
presented to users as two channels, giving a raw bandwidth of
128 kbps, which is a six fold improvement over many modem
connections on analogue telephone lines.
ISDN Connectivity
ISDN is seen by many in the industry as the ramp through which
multimedia networking will gain acceptance. The delivery of
multimedia requires a widespread network capable of delivering
at high data rates. ISDN in the narrow band form is the most
widely available access and delivery medium available. The
installed base of ISDN is growing rapidly (30,000 line per month
in Germany).
In the USA the use of the Internet and the Web is driving the growth of ISDN in some states. [HREF 4]
ISDN is able to provide connections throughout the world. In Europe the
Euro-ISDN agreements between operators enable a reasonable level
of inter-operability. [Ovum94]
Data rates from 64 kbps up to 2 Mbps are commercially available which can meet many needs for transporting multimedia. Call set-up times are under one second.
The interesting feature of ISDN for World Wide Web users is that an ISDN channel offers at least 64kbps which is dedicated to one user, and can be set up very quickly. Paradoxically, on the Internet, the embryonic 'Super Highway' many thousands of users have to compete to use links which are rarely above 2Mbps in capacity. Therefore ISDN access to Web based information systems can provide high quality, responsive information systems. Using remote LAN access products running TCP/IP, ISDN access is relatively easy to implement.
ISDN will be the feeder network for broadband ISDN based on ATM standards. Initially the ISDN and ATM networks will be overlaid on top of each other, but users of ISDN will eventually be able to call an ATM user directly and be allocated an appropriate amount of bandwidth. The development of 'middleware' will enable applications to communicate over mixed networks. [Zakowski94]
Although ISDN could be cheaper, particularly in the UK (currently +300 connect) , it is likely to be cheaper than ATM connections and more widespread in availability for a long time. It is therefore an important tool in bringing multimedia applications to a wide range of users. [Taylor95]
The cost of ISDN hardware was high, but is now decreasing. Terminal adapters are available from +400 upwards, and PC cards from +300 upwards. Video conferencing cards cost around +2500, (BT's VC8000 card). Costs of ISDN equipment are much lower in Germany where the market is larger.
ISDN is accessed through one of two services, named Basic Rate Access (BRA) and Primary Rate Access (PRA). Basic Rate Access (BRA) provides an ISDN user with simultaneous access to two 64 kbps data channels using the existing twisted pair copper telephone cable. [BT94]
The ISDN numbering system is similar to the contemporary telephone numbering system. Each B-channel has its own unique directory number which allows access to different terminal types (such as telex or facsimile devices). Each terminal type has an identity code which ensures that it only communicates with similar terminals on the same ISDN bus.
The equipment available for ISDN includes Terminal Adapters, ISDN internal computer Terminal Adapter cards, Video Conferencing PC cards, and LAN access gateways or bridges, some of which are based on PC cards or stand alone boxes.
A Terminal Adapter (TA)is to an ISDN line what a modem is to a normal analogue telephone line. It is an external device which connects a PC to a ISDN circuit, allowing non-ISDN equipment to use ISDN.
An ISDN card (TA)
acts as an internal terminal adapter in your
computer, just as you can have an internal modem. ISDN cards
offer some advantages over a TA.
Community Telematics
The Manchester ISDN Partnership which comprises the Manchester
HOST, Manchester Metropolitan University (Centre for Employment
Research) and Manchester City Council and Liverpool John Moores
University
[HREF 5],
as the principal partners has been evaluating ISDN
for business and community use. This initiative arose out of a
telematics project Manchester City Council has sponsored in 1991
called the Manchester Host Computer aimed at stimulating the
application of communications and computer technology within the
city and promoting economic regeneration. The aims of the
project were :
To familiarise and provide local business and workers with useful telecommunications and computer technology so that the economy of the area remains competitive within Europe.
To provide people and organisations new to this technology with the confidence to use it efficiently, and innovatively.
To provide fast, flexible communications to enable new networks between people to be formed locally, nationally and internationally.
A number a services were initially provided including electronic mail, fax, telex, bulletin boards, electronic conferencing, local databases, national and international databases. Databases topics include the ICC British Company Directory, the Environment Digest , Health and Safety and EEC information. Internet and X.400 access is available.
The Manchester HOST is a founder member of the Manchester Telematics Partnership, set up to bring together public, private, community and academic organisations to explore, develop and exploit the use of telematics and new communications technologies for local economic and community development.
From the outset of the Host project, it was planned to establish "Electronic Village Halls" (EVHs) - community-based open-access premises. EVHs are located in Manchester's areas of greatest need - predominantly in the inner city. Some have very specific geographical coverage for a particular community. Others specialise in facilities for women including a Womens Business Network [HREF 6], specific ethnic minorities, and the disabled.
EVHs provide a range of facilities (Chorlton), (Chorlton) [HREF 7] including basic IT training, awareness-development, and workshop services. Users include anyone from local community groups and youth clubs to managers of local start-up businesses or community enterprises. One EVH in the Bangladeshi community has established a successful Manchester Asian Trading Network with South East Asia. Manchester Asian Trading Network with South East Asia.[HREF 8]
Connection of these community based organisations with universities, local government, and the Manchester HOST via ISDN LAN to LAN connections will enable co-operative working on electronic publishing projects using the Web and allow organisations to publish and charge for their own information on-line. A community information providers forum has been established to enable co-ordination of these activities, and includes involvement of the City Council, the Bus company, and Citizens Advice bureau.
These initiatives have been possible because there is acceptance that local government in Manchester has a crucial determining role in local economic development and implemention of telematics projects which will create a user base for the 'information superhighway'. There is a role for public information provision as a catalyst for raising the telematics 'literacy' and awareness levels in the local community. [HREF 9] The fear is that without suitable intervention at the local level to support the capacity of all citizens to have access to and actually use the new telematics infrastructures and services, the outcome will simply reinforce the already emerging pattern of inequalities or 'information haves and have nots' amongst people in cities. For instance the potential providers of the 'information superhighway' may not see a public interactive information service as part of their remit.
The Manchester ISDN Partnership has therefore acted as an independant source of expertise and information to local government, community and business organisations on ISDN and increasingly other new technologies such as Asyncronous Transfer Mode (ATM), Electronic Data Interchange (EDI) [HREF 10] , multimedia, video conferencing, and information provision on the Web, so that projects may be designed to deal with these issues.
While there is a belief that telecommunications and telematics projects assist economic development, it extremely difficult to quantify the costs and benefits of local telematics initiatives. Manchester City Council is however continuing to include telecommunications and telematics strands in development projects in the East Manchester and Hulme areas of the city. And in the case of World Wide Web a number of applications have already been developed.
Other services are being considered such as a closed user group
Web, links from Web server into database host, and feeds from
bulletin boards to a Web server.
ISDN Solutions for Web Access
To achieve a local resource base of services and information for
comunity organsiations and small business electronic networking
of information providers and service providers is essential.
High speed dial up access to these resources for users of these
services is needed.
ISDN is well suited in terms of its speed
and flexiblity in permitting tempory connections to different
destinations.
The networking project of the Manchester ISDN
Partnership has been identifying solutions which provide :
A router is used to connect two or more dissimilar networks together which may be LANs, WANs or a mixture of both. A router is the best choice for connectioning networks belonging to different organisations.
The solutions which have been identified fall into the following categories:
Whatever the solution, once a line bit rate of 38.4 kbps or above is achieved, and ISDN solutions can easily provide up to 115 kbps, the usability of graphical applications such as Mosaic improves dramatically. With the sub-second connection time ISDN is an effective networking tool.
Synchronous operation is available at a wide range of speeds up to 128 kbps. Because a PC transmits its data asynchronously, it is impossible to use synchronous transmission with a terminal adapter and thus achieve the high speeds available from ISDN without an extra adapter card.
PC cards can implementing data compression. This is a technique by which modem suppliers limited to 28 kbps of raw bits per second can claim 100 kbps data throughput. The same techniques are applied to ISDN in the V.120 and V.42 bis standards. It is likely that an international compression standard for ISDN will be based on these standards.
In addition to compatibility at the lower layers internal ISDN computer cards require a programming interface. There has been considerable confusion over standards for this interface. In practice the German Common ISDN Applications Interface (CAPI) is the standard most widely available on the cheaper PC cards. Any software which claims to be CAPI compatible should in theory be able to work with any ISDN card providing all the supplementry services available to ISDN such as Call-line Identification. However, in reality, manufacturers do not want their software used with any old card and may design their software in such a way as prevent you from using any card except their own.
The issue of programming interface compatibility will become more complex and important as the need for multimedia support across several bearer services (e.g. ISDN, LANs and ATM ) grows.
Servers and routers exchange information about the network, for example, the names and number of servers available on a network. Each server or router makes a dynamic database of network services. Traffic may be created by broadcasting "I'm here. Who else is there?" If this traffic results in calls over the ISDN B channel being established running costs for an ISDN router would be prohibitive. A technique called spoofing disconnects the line physically when there is no traffic, while maintaining the logical link. This then simulates a permanent line.
Traditional Bridge and Router Suppliers that replied were :-
ISDN Specialists using the Novell Multi-protocol Router with ISDN extensions included
ISDN Connectivity Specialists who responded were :-
Specific costs for all the individual products are not quoted here. Discounts can sometimes be negotiated. The cost of a central router or bridge varies from 1200 to 5000 pounds for hardware and software. At the remote site, the cost can also be high. The range for hardware is from 230 to 1250 pounds and software can cost from 25 to 250 pounds.
Evaluation of the following products has been possible to date :
The AVM MPR software has been used to connect a Netware 3.1 LAN at Manchester Metropolitan University with a Netware 4.02 LAN at Liverpool John Moores University. The network protocols supported by the AVM MPR are IPX, TCP/IP, AppleTalk and OSI. AVM does not make ISDN card for Apple Macs.
AVM's software supports PPP .We are currently still testing the inter - operability of the AVM using the PPP protocol. It has been shown by AVM to be inter - operable using PPP with the several manufacturers routers. Dynamic Bandwidth Allocation is available through channel bundling.
This router is based on the Novell menu system. The documentation is not very easy to follow because you constantly have to jump from book to book to technical note. However, the AVM technical support is particularly good and they have a test server permanently set up.
Using the ISDN Console NLM details can be provided on line usage and call costs both on a per port and per call basis, but the data management seems a little rudimentary. Remote management can be done using the RCONSOLE command.
Netware uses the V42bis data compression technique. It has a current compression ratio of around 4:1 if used between two devices both using AVM ISDN cards.
NetWAYs software using an A1 or B1 ISDN card enables the card to appear as an Ethernet card using Open Data link Interface (ODI) drivers. Once a connection is made, any other LAN protocols run on top of the IPX, providing you have the appropriate third party software. We loaded one commercial IP package and found that the software was utilising only 25% of the proven ISDN line rate. An updated version improved performance to 90%. Using a shareware Winsock package utilisation was also high at around 80%. Other IP packages and possible network bottlenecks including the Web Server itself are now being investigated.
Remote access was tested via a Dataflex Terminal Adapter connected to the Netblazer asynchronously at 38.4 kbps. Configuration of the Netblazer to accept a new modem with new AT commands is difficult and not well documented.
It is possible to use Telnet and Rlogin using any terminal software and dial up the Netblazer.
The remote computer can use any software package with SLIP or PPP to dial a TCP/IP LAN and become a node on the network. Remote users can become a IPX node, via the Netblazer Remote IPX Shell. Netblazer also provides several security features.
These features make it one of the more flexible available, which is important in the context of providing service to many different community organisations with different equipment and requirements. The capacity of the router is ultimately limited by the number of serial line boards (Digiboard recomended) and ISDN cards that can be fitted to the host machine. The software is sold on a licence per port basis. Remote client software costs depend on the number of users, but is currently very reasonable.
Configuration of the router was surprisingly straight forward,
and the new remote client is easy to configure than previous
versions. A bulletin board is available for technical support.
Further tests are in progress.
The design of Web browsers could make more economic use of the
ISDN call charging regime by intelligently caching forward links
as a background task prior to use
The cost to remote users, of hardware and software is still too
high for widespread use of the equipment by many individuals,
but is affordable by academic departments and small companies on
a case by case basis.
There are surprisingly few compatibilty problems that can be
traced to hardware design. The ones that do exist occur when
designers take advantages of additional non standard features in
a chipset to extend performance.
The problem for users is that there is not yet a unified set of
standards that guarantee compatiblity for ISDN remote access in
the same way that modems implement a standard such as V.22 bis.
Users know that a software package using a serial port and Hayes
AT commands will be able to drive a such a modem. Too many
remote access ISDN solutions have propietary hooks, which makes
the provision of a public, high performance service to Web users
difficult without service providers telling their users which
equipment they must use.
Where a programming interface such as the German CAPI has been
used we have found that some degree of interworking can be
achieved. Shareware has been developed for CAPI cards to enable
the use of packet drivers and shareware routing software, so
compatiblity is possible to achieve.
While an extension to PPP promises to support channel
aggregation, further work on standards for asynchronous
transmission up to at least 115 kbps and ISDN channel bonding or
aggregation is needed to enable non - proprietary solutions for
full use of ISDN line speeds.
The implementation of remote access using TCP/IP protocols is
often tied to a specific software TCP/IP 'stack'. Router
manufacturers need to provide more options for users to use
their existing TCP/IP software, which may be different from that
supplied with the router. Some TCP/IP software may not use the
ISDN link efficiently.
[MIP95] "Manchester ISDN Partnership Final Report", February 1995, Centre
for Employment Research, Manchester Metropolitan University,
Manchester,
[Ovum94] "Euro-ISDN Handbook", 1994, Ovum publication,
available from Ovum, Telephone 0171 255 2670.
[Taylor95] Taylor, A and Merabti, M., 1995., "A Review of Multimedia Networking", Advisory Group on Computer Graphics, JISC, UKERNA, Ruderford Laboratories.
[Zakowski94] Zakowski, W., 1994., "A Reference Model for Multimedia
Communications", European ISDN User Forum, Copenhagen, November,
Implementing ISDN Web Access
The use of ISDN to connect LANs and enable remote access to LANs
and LAN based services is feasible and offers good service to
the users. For the most cost effective and manageable use of
ISDN, routers are the preferred solution. For the needs of a low
cost flexible community Web service access via PC cards,
terminal adapters and modems must all be catered for. The Maxpro
router and client software can be supply this functionality, but
a better product for Novell Netware LAN owners is the AVM
Multiprotocol router. Support of asynchronous terminal adapters
and modems can be achieved through a seperate router such as a
Netblazer, or the Netware connect product.
Cost Issues
However the relatively high cost of ISDN in the UK means that
the user or organisation must carefully assess the cost
effectiveness of their use of the Web over ISDN and
participation with other organisations via LAN to LAN
connections.
Advice: -
Do not buy the more expensive ISDN products, prices
will reduce.
Watch your call charges too!
Configuration Problems
The standard of manuals, and ease of configuration of ISDN
equipment, is poor, in common with much equipment in the
computer industry. While this may be tolerable for a LAN
technician, remote users of the Web need software that is as
easy to install as Mosaic or Netscape. The configuration of
routers can initially be quite daunting. Our experience is that
ISDN PC cards are generally easier to use than terminal adapters
because the accompanying software deals with most of the
configuration.
Advice: -
Use PC cards if possible. Look for good technical
support.
Buy ISDN terminal adapters which auto baud.
Hardware Compatiblity
Advice: -
If you want to use different suppliers equipment, it
on evaluation to confirm the products will interwork.
Software Compatiblity
There is potentially widespread compatiblity between ISDN
computer cards. Many cards can implement the same set of
datalink and network protocols. Some PC cards can also emulate
V.110 and V.120 terminal adapters.
Advice: -
Buy a card which supports the CAPI standard
TCP/IP Support
The widespread implementation of PPP for LAN to LAN and remote
access over ISDN is important for creating widespread inter -
operability between different suppliers equipment.
Advice: -
Make sure that some PPP support is available and the
supplier is committed to updating it as new standards appear.
Test the performance of your TCP/IP configuration.
References
[BT94] BT, "Installation notes for ISDN2 lines", 1994., British
Telecom.
Hypertext References
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© Southern Cross
University, 1995. Permission is hereby granted to use this document for
personal use and in courses of instruction at educational institutions provided
that the article is used in full and this copyright statement is reproduced.
Permission is also given to mirror this document on WorldWideWeb servers. Any
other usage is expressly prohibited without the express permission of Southern
Cross University.
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AusWeb95 The First Australian WorldWideWeb Conference
