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Computer Networking MD. ARIFUR RAHMAN LECTURER , GOVT. AZIZUL HAQUE COLLEGE, BOGRA. 1 Network Definition A network can be defined as two or more computers connected together in such a way that they can share resources. The purpose of a network is to share resources. 2 Network Definition(cont…) A resource may be: A file A folder A printer A disk drive Or just about anything else that exists on a computer. 3 Network Definition(cont…) A network is simply a collection of computers or other hardware devices that are connected together, either physically or logically, using special hardware and software, to allow them to exchange information and cooperate. 4 Computer Networks A computer network or data network is a telecommunications network that allows computers to exchange data. In computer networks, networked computing devices pass data to each other along data connections. The connections (network links) between nodes are established using either cable media or wireless media. The best-known computer network is the Internet. 5 Advantages of networking Connectivity and Communication Data Sharing Hardware Sharing Internet Access Internet Access Sharing Data Security and Management Performance Enhancement and Balancing Entertainment 6 The Disadvantages (Costs) of Networking Network Hardware, Software and Setup Costs Hardware and Software Management and Administration Costs Undesirable Sharing Illegal or Undesirable Behavior Data Security Concerns 7 Communication system 8 Component of Communication System 9 Bandwidth: Data Transmission Speed Bandwidth in computer networking refers to the data rate supported by a network connection or interface. One most commonly expresses bandwidth in terms of bits per second (bps). The term comes from the field of electrical engineering, where bandwidth represents the total distance or range between the highest and lowest signals on the communication channel (band). Bandwidth represents the capacity of the connection. The greater the capacity, the more likely that greater performance will follow, though overall performance also depends on other factors, such as latency. 10 Types: On the basis of Transfer Rate 1. Narrow Band: 45- 300 bps.eg. Telegraphy. 11 Types: On the basis of Transfer Rate 2. Voice Band: 9600 bps /9.6 Mbps. 12 Types: On the basis of Transfer Rate 3. Broad Band: < 1Mbps. 13 Methods of Data Transmission 1. Asynchronous Transmission- Transmission & Receive anytime b) Transmission delay is asynchronous c) Each character needs a start and one or two stop bits. *Parity bit. a) 14 Advantages of Asynchronous Transmission Transmission & Receive anytime by Transmitter & Receiver. No Primary Storage Device. Less Installation Cost. Useful in low data transmission rate-eg. Internet. 15 Disadvantages of Asynchronous Transmission- Increase cost of as it remain unused. Comparatively less efficient. Transmission rate is slow. Use in- Computer to Reader /Keyboard /Printer. 16 Methods of Data Transmission 2. Synchronous TransmissionStore data at Primary Storage Device as Block of 80 to 132 characters. Transmission delay time is synchronous. Send header signal And trailer signal . Detect errors in data. 17 Advantages of Synchronous Transmission Comparatively more efficient. Transmission rate high as transmit data simultaneously No time interval between delivering characters. Need no Start & Stop Bits. Less Time. 18 Disadvantages of Synchronous Transmission Need a Primary Storage Device. Comparatively costly. Use inComputer to one or more Computers for long distance data transmission. 19 Methods of Data Transmission 3. Isochronous Transmission- Next version of Synchronous Transmission. The transmission delay time approximately 0. Use in- In Real Time Application Data Transfer. 20 Data Transmission ModeA. Simplex: A e.g. TV, Radio B B. Half- Duplex: A e.g. Walky-Talky. B C. Full- Duplex: A e.g. Mobile, Telephone. B 21 Data Transmission ModeI. Unicast-Mobile II. Broadcast- TV, Radio III. Multicast-Video Conferencing 22 Data Communication MediaA. Cable: A. Co-Axial Cable B. Twisted Pair Cable C. Optical Fiber B. Wireless: Radio wave-10 KHz-1GHz Microwave-<1GHz 23 DIELECTRIC MATERIAL 24 Data Communication Media 1. 2. 3. Cable: A. Co-axial Cable- Copper core Insulator (Dielectric) Braided Conductor 4. 25 TWISTED PAIR CABLE 26 WIRELESS MEDIA Radio Wave: 10 KHz-1GHz Bandwidth-24Kbps 27 WIRELESS MEDIA Satellite Microwave 300MHz-30GHz 28 WIRELESS MEDIA Terrestrial MW Line of Sight 29 WIRELESS MEDIA Transponder INTELSAT 30 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, 31 Transmission Media Two main categories: Guided ― wires, cables Unguided ― wireless transmission, e.g. radio, microwave, infrared, sound, sonar We will concentrate on guided media here: Twisted-Pair cables: Unshielded Twisted-Pair (UTP) cables Shielded Twisted-Pair (STP) cables Coaxial cables Fiber-optic cables 32 Topology ― 3 basic types • How so many computers are connected together? Bus Topology Star Topology Ring Topology Hub 33 Topology 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 Star 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 34 Ring Topology A ring topology connects one host to the next and the last host to the first. This creates a physical ring of cable. Uses a token to pass information from 1 computer to the other. A token is attached to the message by the sender to identify which computer should receive the message. As the message moves around the ring, each computer examines the token. If the computer identifies the token as its own, then it will process the information. A disadvantage of a token ring is if one Computer is broken or down, the message cannot be passed to the other computers. 35 Mesh Topology The mesh topology is the simplest logical topology in terms of data flow, but it is the most complex in terms of physical design. In this physical topology, each device is connected to every other device This topology is rarely found in LANs, mainly because of the complexity of the cabling. If there are x computers, there will be (x × (x–1)) ÷ 2 cables in the network. For example, if you have five computers in a mesh network, it will use 5 × (5 – 1) ÷ 2, which equals 10 cables. This complexity is compounded when you add another workstation. For example, your five-computer, 10-cable network will jump to 15 cables just by adding one more computer. Imagine how the person doing the cabling would feel if you told them you had to cable 50 computers in a mesh network—they’d have to come up with 50 × (50 – 1) ÷ 2 = 36 1225 cables! Mesh Topology 37 Other Topology FULLY CONNECTED PARTIALLY CONNECTED TREE 38 Advantages and Disadvantages of Network Topologies Topology Advantages Disadvantages Bus Cheap. Easy to install. Difficult to reconfigure. Break in bus disables entire network. Star Cheap. Easy to install. Easy to reconfigure. Fault tolerant. More expensive than bus. Ring Efficient. Easy to install. Reconfiguration difficult. Very expensive. Mesh Simplest. Most fault tolerant. Reconfiguration extremely difficult. Extremely expensive. Very complex. 39 Hardware, Software and Networks Peripherals (device) Network Interface Card (NIC) Repeater Hub Bridge Routers Switch 40 Hardware, Software and Networks Peripherals (device) Application Gateway Transport Gateway Router Bridge, Switch Repeater, Hub TCP/IP Model Hybrid Model OSI Model 41 Questions ? 42 43