Computer Networks Done By: Sulaiman Qeshta Ahmed Faris Ahmed Al-Abadelah Jehad Tabash Huseen Abu Yousif

Objectives Learning about: Networks and its benefits Types of Networks Network Technologies Topologies Network Devices Networks Cabling

Networks Computers connect to each other via cable to share resources

Use of Computer Networks Networks for Companies: Resource sharing High reliability Saving money Using client-server model Networks for People: Access to remote information. Person-to-person communication. Interactive entertainment.

Types of Networks There are basically two types of networks: Local-area networks (LAN): ( 10 m - 1km ) LAN are usually designed to cover a small geographical area and are generally used in an office environment. Wide-area network (WAN): ( over 100km ) WAN are usually distributed over a large geographical area (such as the United States).

Network Technologies Point-to-Point Technology Connections between individual pairs of machines. Message may pass through many pairs of point-to-point connections to get from source to destination. Often machines may have multiple point-to-point connections. Large (geographically) networks.

Network Technologies (continue…) Broadcast Technology A single channel is shared by all the machines on the network (nodes or stations). Messages sent by one node are received by all. Use Address field in message to specify target of. Special address to send to all/subset of the stations (broadcast/multicast). Usually small (geographically) networks.

Topologies There are two kinds of Topologies: The physical topology of a network refers to the configuration of cables, computers, and other peripherals. The Logical topology is the method that used to pass the information.

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Topologies ( continue… ) Main types of physical topologies : Star brunch from hub. Ring or loop. Bus or row. linear bus Tree .

Star Networks: A network with radial topology in which a central the point to which all other nodes join. Signals are transmitted from the sending computer through the central node to all computers on the network. Its centralized resources and management. However, because each computer is connected to a central point, this topology requires a great deal of cable in a large network installation. if the central point fails, the entire network goes down.

Star Networks: ( continue…) Advantages of a star topology: • Easy to install and wire. • No disruptions to the network connecting or removing devices. • Easy to detect faults and to remove parts. Disadvantages of a star topology: • Requires more cable length than a linear topology. • If the hub or concentrator fails, nodes attached are disabled. • More expensive than linear bus topologies because of the cost of the concentrators.

Ring Networks: Ring architecture connects each node in a closed loop, Signals ravel from one node to the next in a single direction around the loop. Advantages of a ring topology:- • It is more scalable because the point-to-point links between nodes dose not limit the number of nodes in the ring. Point-to-point: - A direct link between two objects in a network. Disadvantages of a ring topology:- • A failure of any link between a node pair takes the bus down and prevents communication by other nodes.

Linear Bus: A linear bus topology consists of a main run of cable with a terminator at each end. To understand how computer communication on bus you need to be familiar with three concepts: Sending the signal Signal bounce The terminator

Linear Bus: (continue…) Advantage of a linear bus topology: Easy to connect computer or peripheral to a linear bus. Requires less cable length than star topology. The bus is simple, reliable in very small networks, easy to use, and easy to understand. The bus requires the least amount of cable to connect the computers together and is therefore less expensive than other cabling arrangement. It is easy to extend a bus. Disadvantages of a linear bus topology: Entire network shuts down if there is a break in the main cable. It difficult to troubleshoot the bus.

Tree Topology: A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star- configured workstation connected to a linear but backbone cable. Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.

Tree Topology: ( continue…) Advantages of a tree topology: point-to point wiring for individual segments. Supported by several hardware and software venders. Disadvantages of a tree topology: Overall length of each segment is limited by the type of cabling used. If the backbone line breaks, the entire segment goes down. More difficult to configure and wire than other topologies.

Parts of a Networks: Servers: Provide shared resources to users Clients: Use the shared resources from servers Media: Device for connection Shared peripherals: Resources provided by servers such as printers, modems Shared resources: Files, graphics.

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Network Devices: Network Devices

Network Devices: Repeaters Hubs Used to connect together two or more Ethernet segments Various media types Signal quality begins to deteriorate as segments exceed their maximum length Hubs Signal amplification required to allow a segment to be extended a greater distance Ethernet hubs are necessary in star topologies

Network Devices: (continue…) Switches Expansion of the concept in Ethernet bridging Link multiple networks together Two basic architectures Cut-through examines the packet destination address only before forwarding it on to its destination segment Store-and-forward switch accepts and analyzes the entire packet before forwarding it to its destination. Level-3 Switch has IP routing capabilities

Network Devices: (continue…) Bridges Connect separate networks together Different networks types (such as Ethernet and Fast Ethernet) Networks of the same type Bridges map the Ethernet addresses of the nodes residing on each network segment Hi

Network Devices: (continue…) Bridges: (continue…) Allow only necessary traffic to pass through the bridge Bridge determines the destination and source segments If the segments are the same, the packet is dropped ("filtered"); if the segments are different, then the packet is "forwarded" to the correct segment. Additionally, bridges do not forward bad or misaligned packets

Network Devices: (continue…) Routers Filter out network traffic by specific protocol rather than by packet address Routers also divide networks logically instead of physically IP router can divide a network into various subnets so that only traffic destined for particular IP addresses can pass between segments.

Network Devices: (continue…) Network Adapters: A network adapter is the hardware installed in computers that enables them to communicate on a network. They are small and lightweight and can be connected to standard connectors on the back of notebook computers so that the computer and network adapter can be easily transported from network to network

Network Devices: (continue…) Network Adapters: (continue…) The hardware used to make connections between network adapters and different transmission media depends on the type of medium used.

Network Cabling Primary cable types: Cable can be recovered in plastic, rubber, be careful to get the correct type of cable for the type of network card used. Primary cable types: Coaxial Twisted pair Shielded. Unshielded. Fiber optic

Network Cabling: ( continue…) Coaxial cable: Physical description: Coaxial cable consists of two conductors, it consists of hallow outer cylindrical conductor that surrounds single inner wire conductor. The outer conductor is covered with ajacet or shield. Coaxial cable has diameter of from 0.4 to 1 inch.

Network Cabling: ( continue…) Coaxial cable: ( continue…) Applications Television distribution Long-distance telephone transition Short-run computer system links Local area networks Transition characteristics Coaxial cable is used to transmit both analog and digital signals. For long-distance transition of analog signals, amplifiers are needed every kilometers.

Coaxial cable: ( continue…) Conducting core Copper wire mesh or aluminum sleeve Out shield Insulation (PVC,Teflon)

Network Cabling: ( continue…) Twisted pair: The Most expansive and most widely used guided transition medium is twisted pair. Cable showing various layers. Physical description A twisted pair consists of two insulated copper wires arranged in regular spiral pattern. wire pair acts as a single communication link. have thicknesses of from 0.016 to 0.036 inches.

Network Cabling: ( continue…) Twisted pair: (continue…) Applications That used in the telephone network, for local area network supporting personal computer. Twisted pair is much less expensive than the others and is easier to work . It is more limited in terms of data rate and distance. Transition characteristics For analog signal, amplifiers are required about every 2 to 3 km, for digital signal ,repeater are required every 100 or 150 m.

Network Cabling: ( continue…) Unshielded and shielded twisted pair: Unshielded twisted pair (utp) is ordinary telephone wire Recognizes three categories of utp cabling: Category 3.utp cables and associated connecting hardware whose transition characteristics are specified up to 16 MHZ. Category 4.utp are specified up to 20MHZ. Category 5.utp are specified up to 100 MHZ

Network Cabling: ( continue…) Optical fiber: Physical description An optical fiber is a thin(2 to 125 mm). Applications Greater capacity Smaller size and higher weight. Electromagnetic isolation Greater repeater spacing.

Network Cabling: ( continue…) Optical fiber: Transition characteristics Optical fiber system operate in the range of about 10^14 to 10^15 HZ.

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