This topic will help the student understand computer networks, the types of network, network topologies, and requirements for a computer network and also the merits of a computer network.
In this topic, we will cover the following sub-topics
- Types of network
- Basic Hardware Components
- Network topology
Definition; Computer networking is the interlinking made between two or more computers so that they can communicate. A computer that is not connected in the network is called a “stand-alone system.” Mainly networks are developed to help the computers to share the resources. Some of the resources that computer shares are:
- Fax machines
- Other hardware resources.
Basic advantages of using networks
- Sharing of resources and information
- Provision of local facilities without the loss of central control.
- The even distribution of work.
- It has improved communication facilities.
Types of network
- Personal Area Network (PAN); A personal area network (PAN) is a computer network used for communication among computer devices close to one person. Some examples of devices that may be used in a PAN are printers, fax machines, telephones or scanners.
- Local Area Network (LAN); A network covering a small geographic area, like a home, office, or building. Current LANs are most likely to be based on Ethernet technology. For example, a library will have a wired or wireless LAN for users to interconnect local devices (e.g., printers and servers) and to connect to the internet
- Campus Area Network (CAN); A network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, or a military base. A CAN may be considered a type of MAN (metropolitan area network), but is generally limited to an area that is smaller than a typical MAN.
- Metropolitan Area Network (MAN); A Metropolitan Area Network is a network that connects two or more Local Area Networks or Campus Area Networks but does not extend beyond the boundaries of the next town, city, or metropolitan area. Multiple routers, switches & hubs are connected to create a MAN.
- Wide Area Network (WAN); A WAN is a data communications network that covers a relatively broad geographic area (i.e., one city to another and one country to another country) and that often uses transmission facilities provided by common carriers, such as telephone companies.
- Global Area Network (GAN); Global area networks (GAN) specifications are in development by several groups, and there is no universal definition. In general, however, a GAN is a model for supporting mobile communications across an arbitrary number of wireless LANs, satellite coverage areas, etc.
- Internet; the Internet is a worldwide, publicly accessible series of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a “network of networks” that consists of millions of smaller domestic, academic, business, and government networks, which together carry various information and services, such as electronic mail, online chat, file transfer, and the interlinked web pages and other resources of the World Wide Web (WWW).
Basic Hardware Components
All networks are made up of basic hardware building blocks to interconnect network nodes, such as Network Interface Cards (NICs), Bridges, Hubs, Switches, and Routers.
- Network Interface Cards; A network card, network adapter or NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer network. It provides physical access to a networking medium and often provides a low-level addressing system through the use of MAC addresses. It allows users to connect either by using cables or wireless.
- Repeaters; A repeater is an electronic device that receives a signal and re-transmits it at a higher level or higher power, or onto the other side of obstruction so that the signal can cover longer distances without degradation. In most twisted pair Ethernet configurations, repeaters are required for cable runs longer than 100 meters.
- Hubs; A hub contains multiple ports. When a packet arrives at one port, it is copied to all the ports of the hub. When the packets are copied, the destination address in the frame does not change to a broadcast address. It does this in a rudimentary way; it simply copies the data to all of the Nodes connected to the hub.
- Bridges; A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges do not promiscuously copy traffic to all ports, as hubs do, but learn which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address only to that port. Bridges do send broadcasts to all ports except the one on which the broadcast was received.
- Switches; A switch is a device that performs switching. Specifically, it forwards and filters OSI layer two data-grams (the chunk of data communication) between ports (connected cables) based on the Mac-Addresses in the packets. This is distinct from a hub in that it only forwards the datagrams to the ports involved in the communications rather than all ports connected. Strictly speaking, a switch is not capable of routing traffic based on IP address (layer 3) which is necessary for communicating between network segments or within a large or complex LAN. Some switches are capable of routing based on IP addresses but are still called switches as a marketing term. A switch normally has numerous ports with the intention that most or the entire network be connected directly to a switch or another switch that is in turn connected to a switch.
- Routers; Routers are networking devices that forward data packets between networks using headers and forwarding tables to determine the best path to forward the packets. Routers work at the network layer of the TCP/IP model or layer 3 of the OSI model.
The network topology is the study of the arrangement or mapping of the elements (links, nodes, etc.) of a network, especially the physical (real) and logical (virtual) interconnections between nodes.
Basic types of topologies
The arrangement or mapping of the elements of a network gives rise to certain basic topologies which may then be combined to form more complex topologies (hybrid topologies). The most common of these basic types of topologies include Bus, Star, Ring, Tree, and Bus
The type of network topology in which all of the nodes of the network are connected to a common transmission medium which has exactly two endpoints (this is the ‘bus’, which is also commonly referred to as the backbone, or trunk) – all data that is transmitted between nodes in the network is transmitted over this common transmission medium and is able to be received by all nodes in the network virtually simultaneously.
The type of network topology in which each of the nodes of the network is connected to a central node. A point-to-point link in a ‘hub’ and ‘spoke’ fashion. The central node being the ‘hub’ and the nodes that are attached to the central node. All data that is transmitted between nodes in the network is transmitted to this central node, which is usually some type of device that then re-transmits the data to some or all of the other nodes in the network, although the central node may also be a simple common connection point (such as a ‘punch-down’ block) without any active device to repeat the signals.
The type of network topology in which each of the nodes of the network is connected to two other nodes in the network and with the first and last nodes being connected to each other, forming a ring – all data that is transmitted between nodes in the network travels from one node to the next node in a circular manner and the data generally flows in a single direction only.
- d) Tree
The type of network topology in which a central ‘root’ node (the top level of the hierarchy) is connected to one or more other nodes that are one level lower in the hierarchy (i.e., the second level) with a point-to-point link between each of the second level nodes and the top level central ‘root’ node, while each of the second level nodes that are connected to the top level central ‘root’ node will also have one or more other nodes that are one level lower in the hierarchy (i.e., the third level) connected to it, also with a point-to-point link, the top level central ‘root’ node being the only node that has no other node above it in the hierarchy – the hierarchy of the tree is symmetrical, each node in the network having a specific fixed number, f, of nodes connected to it at the next lower level in the hierarchy, the number, f, being referred to as the ‘branching factor’ of the hierarchical tree.
Revision questions: Cm
- a) What is computer network?
- b) What is the importance of networking computers?
- c) Give three disadvantages of networking
- d) Give difference between LAN and WAN
- e) State one difference between a router and a bridge
- f) Identify the functions of the following connectors
- network interface cards
You have learned what the computer network is, types of computer networks, the hardware required when setting a network and also advantages of using computer networks
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