Computer Networks

Computer Networks Shyam Krishna Khadka Engineer Network & Hardware Section IT Directorate, Jawalakhel 2/23/2014

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Objective To be acquainted with: The definitions of networking Network topology Network peripherals, hardware and software Network utility commands

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Definition Interconnection of computers and peripheral equipments (hosts) Used for sharing resources (such as printers and CD-ROMs), exchange files, or allow electronic communications Typical applications: World wide web(WWW), FTP, Remote login

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A computer network can be two computers connected

Switch

A computer network can also consist of, and is usually made for, more than two computers: 2/23/2014

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Why Networking ? - Sharing information • Do you prefer these?

• Or this?

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Why Networking ? Contd… - Sharing hardware or software • Do you prefer these?

• Or this?

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Network Kinds Based on transmission media: Wired (UTP, coaxial cables, fiber-optic cables) and Wireless Based on network size: LAN and WAN

(and MAN) Based on topology (connectivity): Bus, Star, Ring

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LAN and WAN Local Area Networks Small network, short distance A room, a floor, a building Limited by no. of computers and distance covered Serve a department within an organization 2/23/2014

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LAN contd… Examples: Network inside the Student Computer LAB Network inside your home Network inside a building

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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: Intranet System of Nepal Telecom Internet

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Metropolitan Area Network A network that spans a metropolitan area such as a city or suburban area. Eg. Community Schools connected by a network in Biratnagar

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Topology – 3 basic types • How so many computers are connected together? Bus Topology

Ring Topology

Star Topology Switch

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Networking Devices

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Network Interface Card • A network interface card (NIC) is a printed circuit board that provides network communication capabilities to and from a personal computer. Also called a LAN adapter.

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Switch

1. Connects a group of Hosts 2. Switches add more intelligence to data transfer management. 2/23/2014

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Router Routers are used to connect networks together Route packets of data from one network to another Biratnagar Network

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Kathmandu Network

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Networking Media

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Ethernet • Most widely used LAN technology in the world Unshielded twisted-pair • Unshielded Twisted Pair (UTP) Cables are used mostly • Others : Co-axial cable, optical fiber RJ-45 Plug and Socket 2/23/2014

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IP address • 32-bit of number used to identify the host in a network e.g. 10101100.00010101.00001000.01010001 172 .21 .8 .81 IP range : 0.0.0.0 to 255.255.255.255 i.e we can have 2^32 ip addresses Subnet mask • Used to separate network ID and host ID, required for inter network connection 2/23/2014

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Private IP range : 10.0.0.0 – 10.255.255.255 172.16.0.0 – 172.31.255.255 CBS_SD network IP is within this throughout Nepal 192.168.0.0 – 192.168.255.255 2/23/2014

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Subnet mask • Determines the IP range within a network • Determines no. of hosts within a network • Used to separate network ID and host ID, required for inter network connection

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Default Gateway • Interface of the router to the outside network

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DNS server • Domain Name System Server • Resolves hostnames to IP addresses • Eg. http://google.com gets translated into its corresponding ip address(70.232.22.22..)

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Basic networking utilities • Start > Search programs and files> cmd – ipconfig Find my computer’s IP address

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– ping • Checks if the communication between my computer and remote host is working or not Eg. ping 172.16.10.203 (Ping to SD server in ktm)

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Troubleshooting steps • • • • • • •

1) Check network cable plugged/unplugged 2) Check IP address 3) Check hardware driver software - My computer => Right Click => Properties Device manager Network Adapters Intel (853434) Gigabit Network Connection => Right Click => Disable => Enable

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• • • • • • • •

4) Check to nearest switch of network ping switch ip 172.21.11.2 5) Check to router(gateway ip) ping gateway ip Ping 172.21.11.1 6) Check to SD server IP Ping 172.16.10.203

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