COMPUTER COMMUNICATION NETWORKS: USE OF MODERN INFORMATION TECHNOLOGIES FOR INFORMATION RETRIEVAL & DISSEMINATION

COMPUTER COMMUNICATION NETWORKS: USE OF MODERN INFORMATION TECHNOLOGIES FOR INFORMATION RETRIEVAL & DISSEMINATION

Jagdish Arora, Sharan Pal Kaur,
Harish Chandra & R.K. Bhatt

Indian Institute of Technology
New Delhi, 110 016 India

Increasing availability of low-cost computers and associated equipment of varying capabilities promoted the trends towards distributed data processing. Developments in communication techno-logy has made it possible to interconnect such geographically dispersed computing resources of different kinds and makes. A computer communication network is an interconnection of a collection of several computers from which the user can select the service required and communicate with any computer as a local user. A computer communication networks can be viewed as a collection of nodes with computing resources and nodal-switching computers that facilitate communication through a set of transmission links (McGoven, 1989, pp. 2-3). Users can access the network through terminals attached to a node and messages traverse these network through the switching nodes. Since computer communicate using digitized signals instead of electric signals, it requires different transmission facilities than those used for transmitting analogue electrical signals. It is, however, a common practice to use conventional telecommunication links for data transmission by converting digital signals into analogue signals using a process called "Modulation" and the device that performs the conversion is called the MODEM (MOdulator - DEModulator). The current trends are towards the development of an Integrated Service Digital Network (ISDN), which can handle all telecommunications requirements (i.e. voice, data, telemetry, facsimile and video) without discrimi-nation.

Data Communication is an integral part of the modern information storage and retrieval systems in terms of their online access. In the initial stage, the information networks operated in an off-line mode, where in, a query was loaded into a computer which was later matched with the database for relevant bibliographic records. The search results consisting of such records on the subject of query was generated as an output. This process was not satisfactory for effective and efficient retrieval of relevant records. Further progress in computer and communication technology has made it possible to carry out this process in an online interactive mode wherein a user can access an online host via a micro computer from a remote location and can define and redefine his query based on the search results obtained till he is fully satisfied with the final outcome.

The use of communication technology for information retrieval activities gained momentum with the creation of several large databases made available online for shared use through vendors like DIALOG, STN, Datastar, etc. By mid-1970's, several organization had started offering online searches from remote terminals on a variety of online databases. The article, before describing data communication and networks and their use in the libraries and information centres, touches upon their basic concepts, and the types of hardware involved which are considered necessary for users to know.

A simple data communications system typically links input/output devices at remote locations with one or more central processors. Interface elements such as MODEMS and front-end processors are used to accommodate different data communication environments. MODEMs are used to permit the system to switch back and forth from digital data to analog signals that can be transmitted over traditional voice telecommunication lines. A front-end processor is a computer used to monitor and control the data transmission channels and the data being transmitted. The entire data communica-tions activity is controlled by program instructions stored in communications processors and central processors.

The term "data communication" is used to describe the transmission of computerized records having structured format which are generally unintelligible in the transmitted form unlike messages and word processing communications which consist of unformatted text. Basic concepts, proce-dures and standards that are associated with high-speed data communication are given below:

The unit for measuring the speed of data transmission is known as baud. It refers to the number of signal elements transmitted each second. Common speeds available to terminal users accessing remote systems are 300 and 1200 bauds. Faster transmission speeds of 2400, 4800, 9600 and even 24,000 and 96,000 bauds are also available. The speed of transmission depends upon the band-width of the channel being used to transmit the data, the bandwidth is measured in Hertz or cycle per second. The number of bits transmitted per second may not be same as a baud for this very reason.

Within a computer, it is usual to employ parallel data paths which transmit 8, 16, and 32 bits simultaneously. Parallel data buses are employed to achieve much higher transmission speeds where the cost of additional wires or tracks on circuit boards is not significant. While the parallel interfaces allocate dedicated functions to the wires, the serial lines have to carry data and accompanying infor-mation multiplexed in a bit-by-bit form according to a communication protocol. It is common to employ parallel data transfer buses between computers and printers (18 pins, 24 pins, etc.) and disk drives to achieve higher speed and accuracy. Serial transmission is preferable for all long-distance data transmission as the cost of an interface for a long parallel transmission cable becomes prohibi-tive.

The choice for selection of transmission mode rests upon host computer system being accessed. Simplex transmission is suitable only for device such as printers which never transmit information. In full duplex mode, data can be transmitted in both directions along the telecommunication channels simultaneously. In full duplex mode a key pressed on the keyboard results in a series of bits which is transmitted down the channels to the host computer and then 'echoed back' for display on the screen or console which, in turn, serves as a check on the character actually received by the compu-ter. In half-duplex mode data can be transmitted along the channels in one direction at a time; conse-quently the terminal displays characters that were transmitted. Thus the appearance of characters on the screen has no assurance that the host computer has received the transmitted data correctly.

Information may be sent on a line in one of the two modes - asynchronous or synchronous. Asynchronous or start-stop transmission is simpler and is used usually when terminals access remote computer systems. In this case a start code is prefixed and a stop code is suffixed to each character being transmitted. Thus an ASCII character of 8 bits is transmitted as a string of 10 or 11 bits; so a speed of transmission of 300 baud is roughly equivalent to 30 characters per second (cps). In Synchronous transmission, data octets are transmitted in a continuous sequence without start and stop pulses. Each set of synchronous character in a continuous starting of bits which are delimited by using a number of synchronization characters at the beginning of the block and by counting at groups of 8 bits octets after the final synchronous character.

There are various ways by which terminals and computer systems can be connected to other computer systems. Dial-up access employs a telephone line for dialing up the host computer system directly. Although cost effective, this method can not be used for fast and accurate transmission of data. A leased line may be used to transmit large amount of data at a very high speed. A data net-work, is a practical alternate for remote access. The charges for using such a network are usually dependent on the amount of data transmitted and not on the distance.

Computers connected to the transmission lines may establish a path by either circuit switching, packet switching or message switching. Circuit switching connects the two machines via a line and this line is used exclusively by the two machines as long as they communicate. In packet switching, blocks of messages to be transmitted between machines are formed into a packet with sources and destination addresses synchronizing, error detection and control bits and placed on the channel. Packets are routed using the address information. In message switching, all packets are sent to a central computer by all other machines. The central computer, stores and forwards the messages to the appropriate destination addresses. It is more economical to use packet switching for data communication.

Data transmission protocols are sets of commonly agreed rules that are followed to interconnect and communicate between computers in a network. A protocol defines the communication proce-dures and encoding used to interconnect the systems. A number of such protocols are now available and are in vogue. A universally used standard method of interconnecting user terminals to computers is RS 232-C (proposed by Electronic Industries Association, USA). The RS 232-C interface consists of 25 connections, voltage levels, signal transmission rates, timing information and control information. In 1976, CCITT (The International Telegraphy and Telephonic Consulta-tive Committee) also introduced the X.25 standard for the interface between terminal and host computer in a packet switched data network. CCITT introduced another standard X.75 in 1978, for the interlinking of packet-switched data network.

International Standard Organization (ISO) has suggested a layered approach where each layer addresses itself to one aspect of the communication problem. This approach allows each layer to be independently developed. CCITT X.25 standard defines the first three layers of ISO. This standard has been integrated in the network architecture of many vendors. A few important standards and specifications available for various aspects of data transmissions are given below (McGoven, 1989, p. 81):

Network topologies address issues like number of network nodes, concentration of terminals and devices to various locations and how effectively they could be interconnected. Different patterns of interconnections amongst computers in a network are known as network topologies. Computers in different locations may be interconnected in a Mesh Network having multiple message paths between nodes; Star Network having dedicated channels between each station and the control hub. All communication between stations must pass through the hub; Bus Network having a linear topology and station attached by tabs; Tree Network which are bus networks consisting of a series of branches converging indirectly to a control point and offering only one transmission path between any two stations; and Ring Network in which each node is connected to its two adjacent nodes and messages are circulated around the closed ring. A loop network is a ring network in which one master station control transmission. Each of these topologies have their advantages and disadvan-tages. The local requirements and computer configurations involved may be considered while choosing a specific topology (Stallings, 1984).

Communication media are the physical channels through which information is transmitted between computers in a network. Media may be classified as bounded (i.e., wires, cables and op-tical fibres) or unbounded (i.e., ether or airwaves through which radio, Transmitted data can move along simplex, half-duplex or full- duplex lines depending on the needs and protocols involved.

Twisted - pair of wires are inexpensive media used in voice grade telephone lines. They are used for low speed transmission of signals of the order of 1200 bps. Coaxial cables can be used for high-speed data transmission over distance of several kms. Coaxial cables have wide bandwidth of the order of 400 MHz. They may be used in LAN at transmission rates of about 1 Mega bps. Fibre Optics cables are glass fibres that provide high quality transmission of signals at very high speeds of nearly 1000 Megabits per second (Mbps) for distances up to 25 miles.

Radio wave in the very high frequency band (VHF) at about 300 MHz is used for communi-cation between computers in inaccessible locations or for short-range communications. Micro-waves are used for wide bandwidth line-of-sight communication. Rates of transmission up to 20 Giga bps is possible with this media. Communication satellite acts as microwave relay station is the sky. Transponders on the satellite are used to receive, amplify and retransmit signals sent from an earth station. The main advantage of satellite is its wide coverage of a large area and thus it may be used from inaccessible location. A transponder has a very large capacity and can handle about 400 channels, each channel having 64 kbps speed.

A MODEM is a MOdulation-DEModulation device that converts the discrete stream of digital "on-off" electric pulses used by computers into the analog wave patterns used for transmission of the human voice. Demodulator (recovers) the digital data from the transmitted signal. A special type of MODEM called an acoustic coupler is often used in libraries and information units with portable machines, but internal and external direct-connect MODEMs are generally used at permanent stations.

A multiplexer is a device used for transmission of several messages over a single channel using predetermined frequencies within the full bandwidth. The multiplexer operates on the principle that individual channel may require only a small account of actual transmission time; thus the multiplexer acts almost as a timeshare computer allocating use of the single communication lines on a priority basis. A multiplexer is capable of accepting as many as 45 separate channels for transmitting data on a single communication line.

A concentrator is a switch that allocates a particular input to a particular output. While a multi-plexer combines the inputs on a high-speed line; the concentrator allocates a particular input to the line for the duration of its information transfer. The allocation of the output line to a specific input depends on when the request is made, the speed of the input line, and the class or importance of the request.

Front-end processors are installed to handle communication related functions for a mainframe computer so that the later can be fully used for processing applications, be it an inquiry to a database, a printing job or updating a master file, etc... The aim of the front-end processor is to provide an inter-face between the mainframe computer and the network so that the data is passed to and from the mainframe efficiently. The front-end processor is responsible for supervision of the input/output controllers or channels attached to the network, for providing buffering and partial processing of in-coming and outgoing data, for the assembling and dissembling of messages and for error handling.

Communication networks can broadly be grouped into the following categories based on the geographical locations of its computer terminals:

Remote Job Entry Stations are very useful for large organizations to transfer data and program generated in their in- house smaller computer to a larger computer which provides better computing facilities. An RJE provides faster input/output, while the bigger remote computer may be used for massive data processing and for storing large files, all slower operations like printing and scanning may be done at the RJE station.

Local Area Network (LAN) are used to interconnect many computers within a given local area, more often premises of a single organization building. A very high speed of data transmission can be attained within a limited geographic area. The network allows its user to share library programs, databases, languages and special facilities such as an expensive supercomputer. LANs are typically used in a star, bus or ring configuration and they can be classified into high, medium and low speed categories. Some low speed LANs designed for use with personal computers use special cables, while other low-speed networks use telephone wires and digital PBX controllers. Optical fibre cables are used to achieve high-speed transmission of data in a LAN. Regardless of the type of LAN used at a local site, it must be coordinated with the communications elements that link geographically dispersed processing centres.

Wide Area Network (WAN) is used to interconnect a number of widely dispersed computers in various cities of a country or different countries. WANs use communication media maintained by telegraph or telephone companies. These networks usually have land telephone lines, underground coaxial cables, microwave communication and satellite communications. The main objective of such interconnection is to allow users of the network to access specialized library programs, databases etc. available at any of the computers in the network. Two big networks of this type are ARPANET and TYMNET in USA.

Metropolitan Area Network (MAN) refers to the inter- connection within geographical limits of a city or town. Usually referred as "last mile" problem, the MANs shares problems associated with poor telephone network infrastructure of local telephone authority While the satellite based WANs provide excellent communication between remote points irrespective of distance, reliability of intra-city communication in case of MANs are doubtful.

Distributed Data Processing Network consists of many geographically dispersed independent computer systems connected by a telecommunications network. It places the needed data, along with the computing/communications resources necessary to process these data at the end-user's location. DDP networks may be intended for the use of a single organization or many organizations. The possible DDP networks configurations include the star, and the ring arrangements. The Distributed Information Centres (DIC's) of the Biotechnology Information System (BTIS) consist-ing of 9 DIC's scattered in 7 cities of India is an example of Distributed Data Processing Network.

Gateways consist of software and hardware that are required to interconnect networks amongst themselves. Gateways contend with any differences in packet sizes, protocols and addressing methods between the two networks it connect. Two similar LANs are connected by a type of gateway called a bridge. In such cases since the protocols used are same, there is no need to modify the contents or the format of the data packets as they pass from one network to the other. A bridge combines two similar LANs to make one larger network while retaining the individuality of each network in terms of performance reliability and security. Gateways are also used to connect LANs to WANs and WANs, in turn, can be linked through gateways to create national and international data communication networks.

The Videsh Sanchar Nigam (India) has commissioned the International Gateway Packet Switching System (GPSS) to serve as a reliable and economical public data transmission service. The system supports data traffic at speeds ranging from 300 bps to 9.6 kbps. A subscriber to GPSS can make a STD or local PSTN dial- up call to PADS (Packet Assemblers/Dissemblers) installed at the VSNL premises at Bangalore, Bombay, Hyderabad, New Delhi and Pune. The PAD, in turn, is linked to International data networks of many countries around the globe. Users can also take leased lines from customers premises to GPSS.

The communications networks can be grouped into the following three categories based on the technology and communication media used by them :

The Public Switched Telephone Networks (PSTN) are managed by common carriers usually telephone companies/departments the world over. The PSTN generally provide two basic services, the normal dial-up connections to the subscribers and permanent leased connection between two subscribers points. Dial-up lines are often referred to as switched lines because the connection between two telephones requires a series of intermediate switches to be activated. The permanent leased connections provide single traceable line between two subscriber points. The leased lines are generally less prone to noise than dial-up lines.

The PSTN or common carriers can, however, be used for data transmission via MODEM. Sim-ple dial-up connections can be used for low-speed asynchronous and synchronous data transmission up to 2400 bps. Leased lines can operate up to 2400 bps on asynchronous connections, and 9600 bps on synchronous lines.

Analogous to the public telephone network, many domestic common carriers provide data com-munications services via a specialized network called a Public Data Network (PDN). A public data network may provide circuit switching services and/or packet switching (PSDN) and, in future, may be expected to provide many other enhanced services. Examples of Public Data Networks include GTE Telenet, Tymnet, Graphnet, and Faxpac in US; Datapac in Canada, PSS (Packet Switching Service) in UK, Transpac in France, DDX and Venus in Japan, etc. Public Data Networks in the USA such as GTE Telenet and Tymnet are, in turn, interconnected to public data networks in more than 25 countries.

Advances in digital switching and transmission techniques have made possible Integrated Digital Networks and Integrated Digital Services Network (ISDN). An ISDN is a network that provides end-to-end digital connectivity to support a wide range of services, including voice and non-voice services. Users are provided access by a limited set of standard multi-purpose user- network inter-faces. It provides circuit switched 64 kbit/s digital connections. The network also incorporates packet switching capabilities and may also include, subsequently, circuit switched paths at bit rates higher and lower than 64 KBs.

India's first ISDN network at Bangalore is being funded by the Department of Telecommuni-cation (DoT) and developed by the Centre for Development of Telematics (C-DoT). The implemen-tation programme involves the installation of three standard 128 port C-DoT PABX's. The three switches would be installed at the Bangalore Central, Malleshwaram and Ulsoor exchanges and the network would encompass the respective exchange areas. Other important equipment for the ISDN include a central computer to manage the three exchanges, telex gateways, PCU terminals, an IBM PC based terminal, NT boxes with remote power on unit, MODEMs and invertors ("India's first ISDN net this year likely," 1990).

National and international telecommunications services, depending upon their scope and func-tion, can be classified into common carriers, specialized common carriers or value-added carriers (VAN) categories. Common carriers provide large public telephone and telegraph net-works and a broad range of services. Specialized common carriers often use broadband facilities such as microwave/satellite systems to offer public networks that provide a limited number of services. Value-added carriers generally use the telephone lines and transmission facilities of other carriers. Data is received, temporarily stored and organized into packets of characters, and then routed over high- speed leased channels to their destinations. There are also large organizations that are avoiding some of the facilities of local telephone companies and long-distance systems by esta-blishing their own private bypass networks. Most of the international data communication networks used for online searching through remote terminals are value-added carriers. Various national and international networks are further linked to each other through gateways. Since this article focuses on computer communication networks, networks falling into the later two categories are discussed here.

Most of the data networks rely on packet switching techniques first developed on ARPANET, a data communication network of the US Advanced Project Agency of the Department of Defense. Its purpose was to explore network design and to establish connections between computers at centres where ARPA sponsored research was being carried out. The Tymnet and the Telenet were amongst the first few data networks that started operating in North America in 1971 and 1975 respectively. Both the networks are value-added networks (VANs) because their owners lease transmission lines from AT&T (American Telephone and Telegraph Company) and add their own switching and com-munications facilities. Table 1 lists public switched data networks that are currently operational in different countries by dates of introduction (Wessler, 1983):

The progress in networking in India has been rather slow due to the poor extension of telecom-munication networks and overwhelming use of resources and expertise that are available. How-ever, the scene is changing fast. The Department of Telecommunication is setting up a Public Data Network (PDN) and has plans to expand and revamp the existing telephone system. The potential of data networks in India has already been recognized, and few networks have already come into operation.

Networks that are already in operation or in various stages of development may be classified into the following two categories depending upon their scope and objectives:

• Specialized networks (i.e., CALIBNET, DELNET, BONET, ERNET INFLIBNET, BTISNET)

The general networks namely the National Informatics Centre Network (NICNET), the INDO-NET and the VIKRAM are briefly described below :

The satellite based National Informatics Network (NICNET) (Seshagiri et al, 1987) was set up to provide informatics services to the Central and State Government Departments and its organiza-tions. The NICNET provides computing and two-way data communication infrastructure to aid planning and monitoring of schemes and decision-making activities in the Government.

The network consists of Master Earth Station, Remote Micro Earth Stations and a Geosynchro-nous Satellite. The master earth station is located at CGO Complex, New Delhi. It comprises of 13 metre antenna, network control centre and packet switch. Micro earth station connects remotely located district computers with the State computer, which, in turn, are connected to the regional headquarters. Specialized services such as computer-aided design and computer-aided management are also offered over NICNET. The network supports X.25 switch and operates at 1200 bps transmission speed and 19.2 KBs receive speed. The present configuration handles 300 packets (128 bytes each) per second. The host computers are connected to this packet switch.

The NICNET is currently using INTELSAT-V satellite which mainly functions as a relay station between master earth station and micro earth station. The NICNET has used terrestrial communi-cation for distribution of terminals (Local and Remote from NEC-S1000, CEBER-730, CYBER-830, ND-550 or Super AT386 systems) and for development of Local Area Network. Terminals in a building are distributed over RS-232C cable or dedicated lines using line drivers, depending upon the distance involved. The terminals outside the building are connected over data circuits leased from the local telephone authorities. Dial up access using Public Switched Telephone Network (PSTN) is also provided to many users.

The Local Area Network with gateway to the NICNET has been developed at the NIC Head Quarters. Large number of terminals have been distributed from super ATs installed in various buildings. These super ATs are connected to the host machine/packet switch in NIC Head Quarters. Initially, It connected 40 interactive local terminals and 11 minicomputer systems to the in-house mainframe CYBER 170/730 system. These are spread out over a radius of 25 km at Delhi. The remote terminals and the minicomputers are connected by point-to-point data circuits in star confi-guration; 2 concentrators have also been used to support remote terminals. The network facilitates flow of information among 4 national/regional nodes (NEC at Pune, Bhubaneshwar and Hyderabad, ND 550's at State capitals), 32 state/union territory nodes and 439 district nodes.

The NICNET has expanded as a dedicated network having more than 500 nodes geographically distributed over the country, to address the rapidly growing awareness to computerization in different sectors of the Government. Each district information centre consolidates information for monitoring the socio-economic development of the district. Each district is connected to its State's information centre for flow of information from district level to State level. The State centre in turn sends processed information to the regional and the national centres and is also connected to other States. Hence, any user connected to a remote or master earth station can link to any other remote micro earth station. The national centre at the New Delhi is repository of all information systems and conducts research and development of relevant software and hardware tools.

The INDONET (Basu & Saxena, 1987) data network was engineered by CMC Limited for the computer user community in India. It is an integrated information management and distributed data processing facility. The INDONET aims to provide facility for distributed data processing on all India basis to large organizations in the network using the CMC computers for their data processing operations. It also plans for provision of data communications between its users in their respective locations in the network, even if the users are not accessing CMC's nodal computers. Distributed databases in various subjects and access to specialized applications software locally, or in remote locations obviate the need for duplication of software and hardware facilities at each location. The INDONET nodes at Bangalore, Bombay, Delhi, Hyderabad and Pune are connected to the GPSS of the Videsh Sanchar Nigam Limited, thereby facilitating entry to Public Data Networks of other countries.

In phase I, an experimental INDONET Pilot Satellite Network (IPSN) incorporating all the features of the proposed INDONET was worked out. IPSN connects nodes in Bombay, Calcutta, Madras, Delhi, Hyderabad, Bangalore, Vishakhapathnam, Ahmedabad and Pune with IBM 436 computers and MUXs/cluster controllers. The network uses IBM's Computers and Systems Net-work Architecture and 4800 bps leased lines, 9600 bps packet radio links for intra-city connection.

In the second phase, the INDONET would operate as a Star Network with control point in Delhi using root top 3-m earth stations and packet switching. Beside SNA, it will also support X.25 protocols satellite and radio communication the INDONET is expected to cover 35 major cities of India. The CMC Ltd. is closely involved with NISSAT activities in library networking programmes in Calcutta and Delhi.

Vikram (Lahiri, 1991, pp. 13-14) is the packet switched public data network under development by the Department of Telecommunications. This network will initially have 8 switching nodes in Delhi, Bombay, Calcutta, Madras, Bangalore, Hyderabad, Ahmedabad and Pune and 12 remote access nodes with its network management centre located at Delhi. It will support packet switching interface to CCITTs X.25, X.28, X.29 and X.75 recommendations.

CALIBNET (Lahiri, 1991, p. 16) is envisaged as a metropolitan network linking some 38 libraries in Calcutta in a phased manner under the financial support of NISSAT. In the first phase, 7 major libraries are being linked. The participating institutions will collect, process and hold informa-tion on local computers which will be interconnected through a star X.25 packet switched network. One of the participating libraries would do the network control. The software for entire network operation is being developed by the CMC Ltd. The applications to be supported are : Electronic mail, file transfer, remote log-on, database development and document access. Within individual libraries, the functions to be automated are cataloguing, serials control, acquisition and fund accounting, circulation and local user services. The networking provides for global use of current awareness services, SDI, Union catalogues, partial databases and access to national and international databases.

DELNE (Lahiri, 1991, p. 16) is conceived for networking of about 30 libraries in Delhi in its first phase. NISSAT took the initiative for the development of these networks to ensure better utilization of science and technology information resources through resource sharing, to moderate functional load of information centre management and to take care of motivational factors to a large extent by better means of communication. In order to network the libraries in Delhi, a feasibility study was conducted by the Computer Maintenance Corporation (CMC) Ltd. A number of selected libraries have already been networked electronically. An XMAIL communication software, support-ing X.400 based Message Handling System, developed by the Department of Electronics and a Dial-up MODEM have been given by the National Information System for Science and Technology (NISSAT) for exchange of information between the user members, connections between the equipped libraries with DELNET facilities are established using dial-up telephone lines of Delhi Mahanagar Telephone Nigam Ltd. (MTNL). At present, the DELNET provides electronic mail facility as its first application service.

The INFLIBNET (Lahiri, 1991, p. 17) is a major national effort to improve capability in infor-mation transfer and access as support to scholarship, learning, research and academic pursuits. It would link up institutions of higher learning covering all disciplines, about 150 university libraries R&D institutions and national organizations like CSIR, ICAR, DRDO ICMR, ICSSR etc. The network has been conceptualized as a hybrid of satellite based and terrestrial communication system. The network has been designed to offer a plethora of odd services including online catalogue, data-base service, electronic document supply, collection development, etc. A national node has been set up at Ahmedabad to coordinate the network activities. The central node would be connected to four regional nodes which will hold union catalogues and databases.

The ERNET (Education and Research in Computer Network) (Mathur & Ramakrishnan, 1987) was initiated by the Department of Electronics (DoE) during the Seventh Plan (1985-90). It is a computer network for academic and research community in India. Starting with 8 leading institu-tions - the Indian Institute of Technology at Delhi, Bombay, Kanpur, Kharagpur and Madras, the Indian Institute of Science, Bangalore, the National Centre for Software Technology, Bombay and the Department of Electronics, ERNET has already reached hundreds of academic/research institu-tions covering a number of scientific and engineering disciplines. The ERNET project involved setting up campus LANs at all the eight institutions and interconnecting them through a satellite based X.25 WAN for data networking. The ERNET architecture and implementation strategy follows ISO standards and its OSI7 model. Multi-Vendor computing environment is supported with an inter-networking architecture with a variety of underlying sub-networks, viz., campus Local Area Networks (LANs), Wide Area Network (WAN), Metropolitan Area Network (MAN). Connections between ERNET sites are currently achieved using dial-up PSTN lines and is used for electronic mail since January 1989. Satellite-based Wide Area Network (WAN) is currently under implemen-tation. Ethernet (802.3 10 base 5) based Campus LAN are already operational at eight project sites. Non-ethernet LANs are also connected through repeaters, bridges and routers. Applications such as electronic mail, file transfer, remote log-on, database access would be supported in the first phase. document and graphics exchange, voice/computer/video conferencing activities would be addressed in the next phase. The development objective of ERNET is to enhance national capabilities in the areas of design, development, research, education and training on state-of-art concepts of computer networking and related emerging technologies.

The SIRNET (Scientific and Industrial Network) (SIRNET NETletter., 1990-), a project of INSDOC aims at networking all 40 CSIR laboratories under SIRNET was made operational in December 1989. At present, SIRNET provides electronic mail facility as its first application service from the SIRNET servers with a mail number of user nodes. For transmitting a message, a user have to deposit message to one of the SIRNET mail service nodes situated at the INSDOC, Delhi and at its regional centre at Bangalore from where it can be transmitted to its destination which may be any of CSIR laboratory presently linked to the mail node. The SIRNET, in turn, is connected to a large network-ERNET (Educational and Research Network) which is connected to the international network UUNET (Unix User Network) through which other international networks like BITNET, CSNET and JANET are accessible. The SIRNET's mail node at the INSDOC also acts as a gateway to ERNET and through ERNET to other networks. Connections between various laboratories of CSIR are established using dial-up telephone lines, while SIRNET is directly connected to DoE mail server VIKRAM which acts as the clearing node in Delhi ERNET.

The BTISNET (Biotechnology Information System Network) (Immunoinformatics New, 1990-) was established by the Department of Biotechnology at the national level to create and maintain databases and provide network services in six different areas of biotechnology involving 10 specialized centres in 7 cities. The project aims to bridge the inter- disciplinary gaps on information and to establish link among scientists in organizations involved in R & D and manufacturing activities in biotechnology. These specialized centres, designated as Distributed Information Centres, are equipped with Micro VAX II for creation and maintenance of specialized databases in their respective area of specialization. The BTISNET is being installed using the NICNET communication infrastructure for connections amongst the 10 distributed centres and 25 odd user's centres. Most of the DICs and the user centres have already been networked through micro earth stations using X.25 protocols.

The user centres provide access points for information available at the specialized centres and also provide a mechanism to keep the databases up-to-date with the findings and results from their laboratories.

The Bombay Library Network (BONET) (BONET, 1991), sponsored by the NISSAT, aims at promoting cooperation among libraries in Bombay. The National Centre for Software Technology (NCST) one of the first eight participating institutions of ERNET, functions as the central node of BONET. The NCST has made available an HP827 minicomputer (NOVA) with one gigabite disk and a RDBMS software for inter library activities. The BONET will use local dial-up PSTN communication facilities for linking the libraries. the member libraries are, however, urged to use leased lines to fully benefit from the online services. The BONET will offer training related to computerization and networking to the participating libraries.

The idea of sharing information has given the concept of online databases. A database is a non-redundant, multi-usable, independent and physically available set of data elements, stored in an organized and structured manner to allow user to search the information in an interactive mode. The first databases were bibliographic in nature and were online version of existing indexing and abstracting services such as Biological Abstracts, Index Medicus, Chemical Abstracts, etc. By the 1986, only half of all databases were bibliographic. A number of online databases containing textual information, news, statistics, commodity prices, etc., were introduced. A third type of databases holding text of full-length documents started appearing. Several full text of encyclopedia, directories and articles from selected journals are now available online (Arora & Kaur, 1991, pp.2-5).

The number of bibliographic databases available for public searching is growing every year. Most of these databases are available in the United States. Online databases are now increasingly appearing on Compact discs (CD-ROM). Approximately 3600 CD-ROM products are now available for subscription. ADONIS (Article Delivery Over Network Information Systems) project is a land-mark in the electronic publishing wherein a consortium of five major publishers - Academic Press, Blackwell's Scientific Publications, Elsevier Science Publications, Pergamon Press and Springer Verlag, have launched the system known as ADONIS. The project uses combination of laser scanning, printing and digital optical storage technology for storing complete page of over 200 scientific, technical and medical journal articles. These journals would be available on CD-ROM with weekly updates for distribution to selected libraries, who will be licensed to use the system for document delivery.

Online search services host a number of databases in machine readable form which are accessible online through telecommunication links. A user can directly interrogate the databases mounted on host's computer through a computer terminal using a communication package and communication links in two-way interactive mode. These databases are hired/leased to the online search services (also called vendors, spinners or retailers), from their owners (information provider - often the publishers of the printed version of databases). There are more than 500 hosts offering online search services. Some of these hosts are "Umbrella" or "Supermarkets" type covering all fields, while the others host only their own databases. Some of the important online bibliographic search services include: DIALOG, ORBIT, BRS and Datastar in USA; BLAISE and Pergamon Infoline in UK; DIMDI in Germany; Euronet and Diane in Europe; ESA-IRS in Italy; and CAN/OLE in Canada (Arora & Kaur, 1991, p. 4).

The use of these services has become fairly widespread in academic, industrial, government and more recently, information centres and libraries. The external search services offer more and improved retrieval possibilities for carrying out retrospective searches of the published literature than those previously available from the library or information unit.

Because of inadequate communication facilities, online search facilities were almost non-existent in India till the end of 1970's although international online search services such as the DIALOG and ORBIT systems were established in the early 1970's (Haravu, & Nagaraja Rao, 1987). With the innovative developments in communication technology, specially packet-switching, transmission of data over data communication networks such as TELENET and TYMNET became relatively faster, reliable and economical. Since India neither had nodes of any common carrier data networks (TELENET/TYMNET) nor it had a data communication network or a gateway of its own till late 1980's, it was only possible to conduct online searches on Telex Network or through PSTN using a MODEM. In November, 1988, however, the Gateway Packet Switching System (GPSS) was commissioned by the Videsh Sanchar Nigam Ltd. with Packet Assembler/Dissembler (PADs) at Bangalore, Bombay, Hyderabad, New Delhi, and Pune. The GPSS through its PAD connects to a number of international data network of many countries around the globe.

Since early 1980's a number of organizations were doing online search through International Telex Networks and lately through PSTN's, but it got its real momentum in India with the availa-bility of GPSS and other data networks described earlier. With the availability of data communi-cation networks and adequate computer hardware and software support, an organized attempt is being made by the organizations and information systems in India for making the online databases available to the users in India. Although there are several organizations and institutions having online search facilities, the following organizations can be approached in India for making online searches by individual scientists and scholars, who wish to go online to search their information requirements.

The INFOTEL is collaborative venture of the Informatics India (Pvt.) Ltd., Bangalore and the Videsh Sanchar Nigam Ltd. with their service centres in Bangalore, Bombay and Delhi. INFOTEL, through GPSS, can access more than 4500 databases available from all major online systems like DIALOG, ORBIT, BRS, PERGAMON INFOLINE, PROFILE, DATASTAR, STN International as well as knowledge gateways like EASYNET. Annual membership to INFOTEL is available against a requisition fee that allows a user to make search at the INFOTEL's service centre with the assis-tance of their experts. An INFOTEL member, if equipped, can also make his own searches from his premises through a local call to PAD of GPSS. Other services offered by INFOTEL include Interna-tional Electronic Mail Facility, consultancy in setting up online search facility, search aids for online searching, downloading, training programmes, etc. Details for INFOTEL service can be had from the two collaborative institution mentioned above.

The National Centre for Science Information (NCSI) was established with the financial support of the University Grants Commission of India, primarily to cater to the information requirements of scholars, scientists and teaching community in the universities and other learned institutions. The centre subscribes to a number of databases on magnetic tapes, i.e. BIOSIS Preview, CAS, INSPEC Database, etc. for providing Current Awareness Services to the eligible users. The centre, has recently equipped itself to go online specially for retrospective searches on databases available through DIALOG. While the current awareness service provided by the centre is free of cost, the online service is on a cost basis.

Informatics India Pvt. Ltd. is amongst first few private company in India in the information storage and retrieval business. The company represents DIALOG in India and can be said to be leaders in the online access technology and popularizing its use in India. The company undertakes online searches for the interested users, conducts training programmes on online searching, takes turn-key projects for setting-up online search facilities. The services of the Information India Pvt. Ltd. can be had from its online service centres i.e. INFOTEL at Bangalore, Bombay and Delhi. Besides online searching the company has diversified activities, which includes marketing and support of CD-ROM databases, drives and workstations, journal subscription service, software development, online searching and CD-ROM based search facilities, document supply services, etc.

The BTIS was established under the aegis of the Department of Biotechnology, Government of India at the national level in different areas of biotechnology integrating the specialized centres and infrastructural facilities through a nation wide network. The BTIS has following Distributed Infor-mation Centre (DICs) in the universities and R & D institutes in the country engaged in research activities in biotechnology:

Online access facilities has been established at many of these centres for access to DIALOG databases and EASYNET using GPSS communication facilities through its PAD. The scientists from about 25 identified user's centre of the BTIS as well as other scientists working in the field of biotechnology can approach the DIC's for online searching.

The Indian MEDLARS Centre (Formerly The ICMR -NIC Centre for Biomedical Information) (Indian MEDLARS Centre, 1992), housed at the headquarters of the National Informatics Centre (NIC) at New Delhi, was launched jointly by the NIC and the Indian Council of Medical Research (ICMR) in 1985 to cater to the information requirements of medical and biomedical scientists in India. The centre under an agreement with the National Library of Medicine, USA, has facility to access MEDLINE and other MEDLARS databases directly from the National Library of Medicine, USA through the GPSS. Moreover, the centre also has some of the subsets of MEDLARS database on CD-ROM including MEDLINE, POPLINE and TOXLINE for retrospective searches.

Recently, the MEDLARS form 1986 onwards has been mounted on the computers at NIC and is made available online through the NICNET and is accessible from all its 450 district headquarters. A menu driven bibliographical retrieval software BRS/Search is used to search MEDLARS. A user can either approach a nearest NIC office or one of the selected Medical institutes having access to IMC via NICNET. The users can also search the MEDLINE at NIC headquarters on CD-NET. The services from the centre are available to all the users free of cost.

NISSAT, in 1988, under its NACID programme, have set up five regional centres in India for accessing International databases (Lahiri, 1991, pp. 12-13). The online access is currently restricted to DIALOG for most of these centres . These centres are at Indian Association for the Cultivation of Science, Calcutta; National Chemical Laboratory, Pune; INSDOC, New Delhi; Central Leather Re-search Institute, Madras and National Aeronautical Laboratory, Bangalore. The centres used PSTN lines with STD facilities and telex lines to begin with. Currently, the Gateway Packet Switched Services (GPSS) of VSNL (India) are being used for communication. All the five NISSAT's Online Access Centres have trained intermediaries to assist users or to conduct online searches for them. The services were initially subsidized, the full cost is, however, being changed from 1990 onwards.

The development in computer and communication technology has taken a quantum leap. The level of expertise, competence and knowledge available in India in the field of computer communi-cation and networking technology has increased sufficiently to effect establishment of communi-cation links within and outside India. The commissioning of International Gateway packet Switch-ing Services (GPSS) and its PADS (Packet Assembler/Dissembler) by the VSNL (India) in five major cities of India has facilitated cheaper and reliable communication and can be considered as an important landmark. The availability of GPSS has in a way promoted use of the international online search services specially the DIALOG and the EASYNET. Most of the organization in India having online search facilities are using GPSS facilities instead of PSTN lines in preference to the Interna-tional Subscribers Trunk Dialing (STD) facility or rudimentary International Telex Services. The number and kinds of online databases available for remote log-in through various international search services are increasing constantly. More than 4,000 online databases are currently available consisting of fair number of full text databases beside factual and bibliographic databases. More-over, innovative introductions like EASYNET (of Telebase, USA) through VSNL, India are a welcomed change to the information scenario. EASYNET, an information gateway, facilitate online searches over a number of databases and search services without knowing the structure of these databases or the protocols of search service involved. Similarly, DIALOG also offers improved search facilities to its inexperienced users, namely the DIALOG Medical Collection, DIALOG Business Collection and Knowledge Index. These facilities allow searching a number of databases in a given discipline in one go without having to know the structure of these databases.

An increasing number of online databases are appearing on the compact disc which allows local limitless access and hence do not involve communication cost. Today's information scenario, thus, presents a number of lucrative options for an information scientist to choose from, who, in turn, is require to make a conscious selection with regards to procurement of CD based products in preferen-ce to online searching or vice-versa. While the most used services can better be procured on com-pact disc in preference to printed format, the lesser used databases can be searched online whenever required. The procurement of secondary services in printed format should be discouraged.

The use of currently operational local library networks namely DELNET, BONET and CALIBNET should in no way be limited to the electronic mail facilities. Other features like database accord , file transfer, remote log-on, document and graphic exchange, video conferencing and facsi-mile transmission should be added in phased manner. The use of common integrated package with built in network interface should be introduced and promoted. More advanced general and special purpose networks like ERNET, SIRNET and NICNET should be made available for use to the libraries and information community and their users. Direct interaction between users and informa-tion banks through networks should be promoted for better awareness and increased use.

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