CHAPTER TWO LITERATURE REVIEW
2.1 Computer Network
Computer networks can also be said to be a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information. Where at least one process in one device is able to send/receive data to/from at least one process residing in a remote device, then the two devices are said to be in a network. Networks may be classified according to a wide variety of characteristics such as the medium used to transport the data, communications protocol used, and topology, their roles and responsibilities and geographical area.
A computer network can be defined as a grouping or interconnection of different computer on a single platform for information exchange among various nodes (clients) or independent functioning computers or workstations (Agbasi, 2012). In a technology context, network is usually short for "computer network" or "data network" and implies that computers are the things sharing the meaningful information. At a conceptual level, all data networks consist of nodes, which refer to any computer or digital device using the network and links, the physical connections that carry messages between nodes (Zhirkov, 2004).
2.2 Medium Used to Transport Data
Transmission media is a medium through which data can be transmitted over a long distances. The speed or rate at which data is transmitted over a communication channel is denoted by a parameter called bandwidth. The various transmission media are two wire open lines, twisted pair, coaxial cable, optical fibres, and all the transmission media listed above uses guided media. It is also possible to transmit information into free space, using a high frequency electromagnetic wave. Electromagnetic waves in the frequency range of 500MHz and above are known as microwaves. Some of the unguided transmission media (wireless) are Geo-stationary satellites, light-of-sight microwave, radio waves and infrared.
2.3 Protocols
Communications protocols define the rules and data formats for exchanging information in a computer network, and provide the basis for network programming. Well-known communications protocols are Ethernet, hardware and link layer standard that is ubiquitous in local area networks, and the internet protocol suite, which defines a set of protocols for internetworking, i.e. for data communication between multiple networks, as well as host-to-host data transfer, and application- specific data transmission formats.
2.4 Topology
Topology is geometrical arrangements of nodes. Nodes refer to various computer resources and communication devices. The following are different classes of network based on the topological structure.
Bus network: In a bus network, all nodes are connected to a single communication channel called bus. It is also referred as a time-shared bus.
Star network: In a start network, each node is connected by means of a dedicated point-to-point channel to a central node called server that act as a switch.
Ring network: Nodes in a ring network are connected in the form of a closed loop.
Mesh network: In a mesh network, each pair of nodes is connected by means of an exclusive point-to-point link.
Tree network: A tree network is another form of a bus. Several nodes are connected into a hierarchical form.
2.5 Roles and Responsibilities of Computer Network
Networks vary considerably in terms of the roles and responsibilities of the computers on that network and the relationships that tie those machines together. A computer totally disconnected from other devices is typically referred to as a stand- alone machine.
When several computers are interconnected, but no computer occupies a privileged position, the network is usually referred to as a peer-to-peer network (Balasubramanian et al, 2006). In this type of network, every computer can communicate with all the other machines on the network, but in general each one stores its own files and runs its own applications.
With a client-server network, one or more servers will perform critical functions on behalf of the other machines (the clients) on the network (Aguboshim, 2008). These functions might include user authentication, data storage, and the running of large, shared, resource-intensive
Typically, both peer-to-peer and client-server networks rely on a shared Internet connection for access to external resources of these basic network structures.
Another type of network that's been rapidly gaining in popularity over the past decade is the cloud-based network. In this model, an organization pays a third-party vendor to host data, applications and other resources on servers and manages those resources via a web browser. A cloud-dependent network can be simpler, cheaper, and greener than a client-server network since you aren't buying, maintaining and powering your own servers. However, it’s not necessarily the right solution for every organization, particularly those that handle and store sensitive client data or health records.
