BASIC CONCEPTS OF NETWORK

INDEX  Definition & applications of computer network  Components of computer network  Network benefits  Disadvantages of computer network  Classification by their geographical area  Network classification by their component role  Types of servers

DEFINTION & APPLICATIONS  DEFINTION: A computer network is defined as the interconnection of two or more computers. It is done to enable the computers to communicate and share available resources.  APPLICATIONS: i. Sharing of resources such as printers ii. Sharing of expensive software's and database iii. Communication from one computer to another computer iv. Exchange of data and information among users via network v. Sharing of information over geographically wide areas.

COMPONENTS OF COMPUTER NETWORK  Two or more computers  Cables as links between the computers  A network interfacing card(NIC) on each computer  Switches  Software called operating system(OS)

SHARING RESOURCES  Types of resources are: 1. Hardware: A network allows users to share many hardware devices such as printers, modems, fax machines, CD ROM, players, etc. 2. Software: sharing software resources reduces the cost of software installation, saves space on hard disk.

OTHER BENEFITS OF COMPUTER NETWORK o Increased speed o Reduced cost o Improved security o Centralized software managements o Electronic mail o Flexible access

DISDAVATAGES OF NETWORKS o High cost of installation o Requires time for administration o Failure of server o Cable faults

CLASSIFICATION OF AREA BY THEIR GEOGRAPHY NETWORK LANWAN MAN

LOCAL AREA NETWORK(LAN)  LAN is a network which is designed to operate over a small physical area such as an office, factory or a group of buildings.  LAN’s are easy to design and troubleshoot  Exchange of information and sharing of resources becomes easy because of LAN.  In LAN all machines are connected to a single cable.  Different types of topologies such as star, tree, bus, ring, etc Can be used  It is usually a privately owned network.

WIDE AREA NETWORK(WAN)  When network spans over a large distance or when the computers to be connected to each other are at widely separated locations, a local area network cannot be used. A wide area network(WAN) is installed.  The communication between different users of WAN is established using leased telephone lines, satellite links and similar channels.  It is cheaper and more efficient to use the phone network for the link.  Most WAN networks are used to transfer large blocks of data between its users.

METROPOLITAN AREA NETWORK(MAN)  It is in between LAN & WAN technology that covers the entire city.  It uses similar technology as LAN.  It can be a single network such as cable TV network, or a measure of connecting a number of LAN’s o a large network so that resources can be shared LAN to LAN as well as device to device.

PARAMETERSLANWANMAN Ownership of network PrivatePrivate or public Geographical area covered SmallVery largeModerate Design and maintenance EasyNot easy Communication medium Coaxial cable PSTN or satellite links Coaxial cables, PSTN, optical fibre, cables, wireless BandwidthLowHighmoderate Data rates(speed) HighLowmoderate DISTINGUISH BETWEEN LAN,WAN,MAN

COMPUTER HARDWARE  When we refer to network hardware, we are talking about a range of electronic devices that can be interconnected in such a way as to allow the transmission of communication signals between a number of workstations.  These devices range from simple generic hubs to sophisticated proprietary hardware such as routers and gateways.

Network Interface Cards  Network Interface Cards (NICs) are the most common type of network hardware on a network.  Every computer on network will contain at least one NIC.  NICs contain the electronic components that establish and control network communications.  The NIC is the principal hardware device that differentiates between a networked computer and a stand-alone computer.

Hubs  Hubs are one of the most basic pieces of networking equipment available.  Physically a hub is a box with a number of RJ45 ports (typically between 4 and 32) that allows you to connect several networking devices together using twisted pair (CAT 5) network cables.

Hubs  Hubs have no intelligence, meaning they cannot be programmed or have a memory of devices that are plugged into its ports.  They are quite suitable for small networks but tend to perform poorly on large networks.

Switches  Switches look nearly identical to hubs, but a switch generally contains more ‘intelligence’ than a hub.  Unlike hubs, network switches are capable of inspecting the data packets as they are received, determining the source and destination device of that packet, and forwarding that packet appropriately.

Switches  By delivering messages only to the connected device that it was intended for, network switches conserve network bandwidth and offer generally better performance than hubs.  Most switches are active: that is, they electrically amplify the signal as it moves from one device to another.

Bridges  Bridges are devices that allow you to segment a large network into two small, more efficient networks.  If you are adding an older wiring scheme and want the new network to be up-to- date, a bridge can connect the two.

Bridges  A bridge monitors the information traffic on both sides of the network so that it can pass packets of information to the correct location.  Most bridges can ‘listen’ to the network and automatically figure out the address of each computer on both sides of the bridge.  The bridge can inspect each message and, if necessary, broadcast it on the other side of the network.

Routers  Routers translate information from one network to another; it is similar to a bridge with extra intelligence.  Routers select the best path to route a message, based on the destination address and origin.  The router can direct traffic to prevent head-on collisions, and is smart enough to know when to direct traffic along back roads and shortcuts.

Routers  While bridges know the addresses of all computers on each side of the network, routers know the addresses of computers, bridges, and other routers on the network.  Routers can even ‘listen’ to the entire network to determine which sections are busiest - they can then redirect data around those sections until they clear up.