5 . Alphonse F Trezza has defined networks as “a formal organization among libraries for co-operation and sharing of resources, in which the group as a whole is organized into subgroups, with the exception that most of the needs of a library will be satisfied within the subgroups of which it is a member.”

6. The term ‘network’ has been defined by Greenberger and Arnofsky as a mode for sharing resources and linking otherwise incomparable procedures and formats of different systems and organizations”. Miller has defined it as “a cooperative system established by libraries and information centres which are brought together by common subject, geographic proximity to share informational resources, human resources and all other elements essential for providing effective information service.”

7. Accordingly to United Nations Information System for Science and Technology (Unisist), “Networking is a set of inter-related information systems associated with communication facilities, which are co-operating through more or less formal agreements and institutional agreements in order to jointly implement information handling operations with a view to pooling their resources and better serving the users. They generally follow identical or compatible rules and procedures.”

8. From the above definitions, it is clear that a network is a co-operativesystems of sharing resources among two or more libraries through aformalinstitutional agreement, common pattern of exchange of information among the libraries by the help of communications system.

The networks are often called information networks, electronic networks, library networks etc.

4 TYPES OF NETWORKS

Networks are mainly of two types, these are as follows:

41 LOCAL AREA NETWORK (LAN)

A LAN could be said to be a set of data processing devices interconnected through cable. It sends and receives data transmitted over relatively short distances. The type of data transmitted in LAN may include mail (messages and notes), manuscripts, reports, computer files and software.

42 WIDE AREA NETWORK (WAN)

Wide Area Network System (WAN) usually covers distance between nodes geographically scattered in hundreds or thousands of kilometres apart. It is generally a mixed-media network system using a combination of terrestrial lines and satellite communication system.

5 TOPOLOGY

The network topology is the arrangement of nodes on a network. This includes the physical arrangement or the geographic pattern by which the nodes are connected. It also includes the logical arrangement; the possible destinations to which each can route data. Inter-connection of system can be achieved in many ways, but basically there are three most important methods, viz. point-to- point, multi-point/multi-drop and broadcasting.

9 .We will consider here the design of hardware components called nodes.

These nodes, when linked, form patterns, that are classified as star like topologv: tree-like topology; ring topology and meshed topology.

10. The successful topology for BD-AGRINET depends on several factors like funds, trained personnel, hardware, software and communication facilities that continually influence their growth. The following number of terminals in BD- AGRIGNET will be connected to national and international networks.

Theinstitutions are identified as follows:

(1) Agricultural University Libraries in Bangladesh.

(2) Agricultural Libraries in Dhaka City.

(3) Agricultural College Libraries in Bangladesh.

(4) Agricultural Research Institutes Libraries in Bangladesh.

51 FORMS OF TOPOLOGY

The star network is one in which one member of network holds the majority of the resources while at the same time. all other network members use the same resources. Figure 1 illustrates such a network, with member A possessing virtually all the resources, while the other network members B, C, D & E make use of resources.”’

The tree network topology, on the other hand, is suitable for an environment where network members share resources locally. In this topology the nodes are connected hierarchically. Here mini computers are used as intermediary nodes and micro-computers as end nodes. It makes for reduced communication costs as several terminals can be connected to a single communication line.

In this topology each network members is connected with other members like a ring. This topology generally suits a network in a building on a small campus with well-defined but limited operations.

Dr. Md. Hanif Uddin

Assistant Professor ,Dept. of Information Science and Library Management,
University of Dhaka
Dhaka 1000, Bangladesh

&

Md.