Computer Network: It is group of interconnected computers and devices which are sharing the same communication infrastructure and communication protocols for the purpose of sharing computer resources. Categories of CN: LAN WAN MAN

1. LAN: The CN is said to be LAN if the interconnected computers and devices are situated Within the limited geographical area or limited vicinity The communication infrastructure must owned by the organization owning LAN rather than any third party as a common carrier. 2. WAN: The CN is said to be WAN if the interconnected computers and devices are situated At distant geographical locations The communication infrastructure must be owned by third party as a common carrier.

3. MAN: The CN is said to MAN if the corporate LANs lactated at dispersed locations are interconnected with the help of the WAN links. Advantages of CN: Data and equipment sharing Sharing software resources/programs Fast data communication Sharing data within organization and outside the organization Flexible working environment Maximum resource utilization Centralized management & security Load sharing/load balancing Alternative resources backup Cost effectiveness

LAN Topology It means the physical layout of the network (LAN configurations with respect to devices, equipments and network media). There are following LAN topologies Bus topology Star topology Ring topology

1. Bus topology: Definition: In bus topology all computers on the LAN connected along a linear bus i.e. Ist computer is connected to 2nd and 2nd computer is connected to third and so on and at the both ends of network terminators are introduced. Network Hardware devices and equipments: Network media: Coaxial (Thinnet and Thicknet) Connector: BNC, BNC-T, Terminators Devices: Repeaters, NIC with BNC connector Access Method: CSMA/CD Technology: Ethernet

Advantages of Bus: Simple Configuration Inexpensive Easy Network extension If a computer fails network remains unaffected It is popular topology It has no central controller (connecting device) Disadvantages of Bus: Trouble shooting is difficult If there is break in the media whole network goes down Does not recommended for large networks It not so much reliable

Star Topology: In star topology all the computers on network are connected to one or more central controller (connecting device). this central connecting device is known as hub. All the network cables come from this central device. Network Hardware: Device: HUB/ Switch, NIC with RJ- 45 option, Repeater Network media:UTP/STP (Cat-III, IV, V) Connector:RJ-45 Access method: CSMA/CD Technology: Ethernet

Advantages of star Topology: Network trouble shooting is easy If one PC’s cable segment fails it does not affect the other network The network is more reliable If a computer fails network remains unaffected Disadvantages of Star Network: If the central controller fails, the entire network fails The of no ports on Hub limits the total number of pc supported This network is costly It is recommended topology only for large networks Network extension is difficult as compared to bus

Ring topology: In Ring topology all computer on the network form a continuous loop i.e. all computers are connected along a circular ring first and last computer are also interconnected to each other. The data flow in the ring will be one direction. An electrical signal called token circulates continuously on the ring. Network Hardware: Network media:IBM cabling system (twisted pair, coaxial, fiber optic) Connectors:corresponding to cables used Devices:Multiple station access units (MAU), NIC for each computer Access method: Token Passing

Advantages of Ring Topology: High data transfer rate More reliable Disadvantages: Costly If central MAU fails all network goes down In one is down all the other network activity affects

Mesh Topology It is network setup where each computer on the network is interconnected through redundant links. Advantages of Mesh Topology –Guaranteed communication –If one or more links are down even then communication is guaranteed –It is most feasible for wireless networks –Messages can take any route to reach its destination

Disadvantages of mesh Complexity Difficult configuration Expensive solution

Tree Topology In tree topology multiple star topology networks integrated to form the bus of star topology network. This topology is also called hybrid topology. In tree topology network only hub/switches are connected which act as roots of tree. Advantages –Future network capacity expansion