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1.introduction to computer networksPresentation Transcript
Computer Communication & Networks Introduction to Networking Made by: Sidra !
What is a Network?A network consists of 2 or more computersconnected together, and they can communicateand share resources
Why Networking?• Sharing information — i.e. data communication • Do you prefer these? • Or this?
• Sharing hardware or software • E.g. print document• Centralize administration and support • E.g. Internet-based, so everyone can access the same administrative or support application from their PCs
How many kinds of Networks?• Depending on one’s perspective, we can classify networks in different ways • Based on transmission media: Wired (UTP, coaxial cables, fiber- optic cables) and Wireless • Based on network size: LAN and WAN (and MAN) • Based on management method: Peer-to-peer and Client/Server • Based on topology (connectivity): Bus, Star, Ring …
LAN - Local Area Network• Local Area Network (LAN) • Small network, short distance • A room, a floor, a building • Limited by no. of computers and distance covered • Usually one kind of technology throughout the LAN • Serve a department within an organization • Examples: • Network inside the Student Computer Room • Network inside your home
WAN – Wide Area Network • A network that uses long-range telecommunication links to connect 2 or more LANs/computers housed in different places far apart. • Towns, states, countries • Examples: • Network of our Campus • Internet Your home USA WAN Campus
MAN - Metropolitan Area Network Larger than a LAN and smaller than a WAN - example: campus-wide network - multi-access network Technologies: coaxial cable microwave
Network Management MethodPeer to Peer Network• Peer-to-peer network is also called workgroup• No hierarchy among computers all are equal• No administrator responsible for the network Peer-to-peer
Network Management Method• Advantages of peer-to-peer networks: • Low cost • Simple to configure • User has full accessibility of the computer• Disadvantages of peer-to-peer networks: • May have duplication in resources • Difficult to uphold security policy • Difficult to handle uneven loading• Where peer-to-peer network is appropriate: • 10 or less users • No specialized services required • Security is not an issue • Only limited growth in the foreseeable future
Network Management MethodClients and Servers • Network Clients (Workstation) • Computers that request network resources or services • Network Servers • Computers that manage and provide network resources and services to clients • Usually have more processing power, memory and hard disk space than clients • Run Network Operating System that can manage not only data, but also users, groups, security, and applications on the network • Servers often have a more stringent requirement on its performance and reliability
Network Management Method• Advantages of client/server networks • Facilitate resource sharing – centrally administrate and control • Facilitate system backup and improve fault tolerance • Enhance security – only administrator can have access to Server • Support more users – difficult to achieve with peer-to-peer networks• Disadvantages of client/server networks • High cost for Servers • Need expert to configure the network • Introduce a single point of failure to the system
Topology ― 3 basic types• Bus Topology • Simple and low-cost • A single cable called a trunk (backbone, segment) • Only one computer can send messages at a time • Passive topology - computer only listen for, not regenerate data
Topology ― 3 basic types Advantages of a bus topology: uses less cable compared to other physical topologies like star works well for small networks does not need a central device, such as a hub, switch, or router Disadvantages of a bus topology: slower access to the network and less bandwidth due to the sharing of the same cable by all devices challenging to identify and isolate problems break at any point in the bus cable can disable the entire bus network
Topology ― 3 basic typesStar Topology • Each computer has a cable connected to a single point • More cabling, hence higher cost • All signals transmission through the hub; if down, entire network down • Depending on the intelligence of hub, two or more computers may send message at the same time Hub
Topology ― 3 basic types Advantages of a Star Topology: upgradeable, flexible, and reliable easy to design and install diagnosing problems relatively easy allows for more throughput than any other topology Disadvantages of a Star Topology: requires a lot of cable to connect computers . expensive to build because of the additional cost of cables and devices
Topology ― 3 basic types• Ring Topology • Every computer serves as Ack T T a repeater to boost signals T • Typical way to send data: T dat T dat • Token passing a a • only the computer who gets the token can send T data T T Ack • Disadvantages T Ack dat • Difficult to add computers a • More expensive T • If one computer fails, whole network fails T Ack
Network Devices: Repeaters A repeater receives the signal, regenerates it, and passes it on. Repeaters are used mainly at the edges of networks to extend the wire so more workstations can be added.
Network Devices: Hubs Using a hub changes the network topology from a linear bus, where each device plugs directly into the wire, to a star. Hubs come in three basic types: Passive Active Intelligent
Network Devices: Bridges Bridges operate at the data link layer of the OSI model. The function of the bridge is to make intelligent decisions about whether or not to pass signals on to the next segment of a network. When a bridge sees a frame on the network, it looks at the destination MAC address and compares it.
Network Devices: Switches Switches learn certain information about the data packets that they receive from computers on the network. They use this information to build forwarding tables to determine the destination of data sent by one computer to another on the network. They help segment a network and reduce network traffic congestion.
Network Devices: Routers Routers operate at the Network layer of the OSI model. They are slower than bridges and switches but make "smart" decisions on how to route packets. Routers are capable of segmenting the network.