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Welcome to Computer Networks


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Welcome to Computer Networks

  2. 2. What is computer network? <ul><li>A network is group of computers interconnected with each other to exchange information or resource. </li></ul><ul><li>A computer network is collection of interconnected autonomous computers interconnected in a single technology. </li></ul><ul><li>Two computers are said to interconnected with each other if they share some information between them. </li></ul>
  3. 3. What are the advantages of having computer network? <ul><li>1.Increased communication capabilities. </li></ul><ul><li>2.File sharing: Network offer quick and easy way to share files directly at a rapid speed thus saving time and integrity of files. </li></ul><ul><li>3.Resouce sharing : All computers in a network can share resources like printer, scanner, modem, fax machines, hard disk. </li></ul><ul><li>4. Security: Specific directories can be password protected to limit access to authorized users. Also, files and programs on a network can be designated as &quot;copy inhibit&quot; so you don’t have to worry about the illegal copying of programs. </li></ul><ul><li>5. It is also possible to share data files across the network by creating a share on the hard drive and allowing other people access to that information. </li></ul><ul><li>6.Increases the productivity. </li></ul><ul><li>7. You can connect all the computers which are connected through a network to the internet by using a single line. So it means that you can save the connection cost for each computer but you internet connection must be fast. </li></ul><ul><li>8. Internet connection sharing - Using a home network, multiple family members can access the Internet simultaneously without having to pay an ISP for multiple accounts. You will notice the Internet connection slows down when several people share it, but broadband Internet can handle the extra load with little trouble. Sharing dial-up Internet connections works, too. </li></ul><ul><li>or </li></ul><ul><li>Connect your entire office to the Internet through one line. </li></ul>
  4. 4. What are the disadvantages of computer network? <ul><li>1.Network faults can cause loss of data. </li></ul><ul><li>2.Network faults could lead to loss of resources. </li></ul><ul><li>3.Systems open to hackers. </li></ul><ul><li>4.Could become inefficient. </li></ul><ul><li>5.Could degrade to performance. </li></ul><ul><li>6.Resources could be located too far from users. </li></ul><ul><li>7.As a work group user cannot Login from other work group machine within LAN network. </li></ul><ul><li>8.User also cannot login from any remote machine from WAN environment. </li></ul>
  5. 5. What are the different types of computer networks? <ul><li>PAN( personal area network) : Network that is meant for one person </li></ul><ul><li>Eg: A wireless network connecting a computer with it’s mouse, keyboard, printer is PAN. Covers 1m distance only. </li></ul><ul><li>LAN (local area network) : LAN’s are privately owned network which covers a room, building or a campus ( 10m, 100m, 1km) of distance. </li></ul><ul><li>LAN’s are widely used in offices, companies, industries. </li></ul><ul><li>Characteristics: </li></ul><ul><li>* Lan’s are restricted in size </li></ul><ul><li>*Lan’s uses transmission media as cable , to which all the machine are attached. </li></ul><ul><li>*Lan’s basically uses Bus and Ring Topologies( network structure) to broadcast. </li></ul><ul><li>Traditional Lan’s runs at the speed of 100Mbps and newer Lan’s runs at the speed of 10Gbps. </li></ul><ul><li>Lan’s are un-switched ( they don’t have routers). </li></ul>
  6. 6. <ul><li>MAN (metropoliterian area network): MAN covers city ( about 10Km) in distance. </li></ul><ul><li>The best example of Man is the CABLE TV NETWORK available . </li></ul><ul><li>Cable TV is not the only MAN ,development in high speed wireless internet access resulted in MAN. </li></ul><ul><li>MAN’s are also un-switched ( i.e don’t have routers) </li></ul><ul><li>WAN (wide area network): A wide area network covers a large geographical areas like country or a continent ( about 100Km, 1000Km, 10,000Km)in distance. </li></ul><ul><li>In WAN, subnet consist of two components Transmission lines like copper cable, optical fiber ( move bits between machines) and Switching elements or routers (specialized computers or devices that connects 3 or more transmission lines, when date arrives to incoming line, router choose an outgoing line on which to forward them. </li></ul>
  7. 7. <ul><li>Hosts ( user’s computers) are connected to subnet. </li></ul><ul><li>Subnet is owned and operated by telephone company or isp. </li></ul><ul><li>The subnet is collection of communication lines and routers ( but not hosts). </li></ul><ul><li>The job of subnet is to carry message from host to host . </li></ul><ul><li>In most WAN’s , the network contains numerous transmission lines , each one connecting pair of router. If two routers do not share a transmission line , wish to communicate they must do this indirectly via other router . </li></ul><ul><li>When a packet is sent from one router to another via one or more intermediate routers, the packet is received at each intermediate router in its entirety , stored until the required output is free, and then forwarded. </li></ul><ul><li>This principle is known as “store and forward or packet switched subnet”. </li></ul>
  8. 8. What are the types of transmission media ? <ul><li>Signals are usually transmitted over some transmission media that are broadly classified in to two categories. </li></ul><ul><li>Guided Media: </li></ul><ul><li>These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial cable use metallic that accept and transport signals in the form of electrical current. Optical fiber is a glass or plastic cable that accepts and transports signals in the form of light. </li></ul><ul><li>Unguided Media: </li></ul><ul><li>This is the wireless media that transport electromagnetic waves without using a physical conductor. Signals are broadcast either through air. This is done through radio communication, satellite communication and cellular telephony. </li></ul>
  9. 9. What are the different types of network hardware? <ul><li>NIC ( network interface card) </li></ul><ul><li>Repeater </li></ul><ul><li>Switch </li></ul><ul><li>Router </li></ul><ul><li>Hub </li></ul><ul><li>Modem </li></ul><ul><li>Server </li></ul><ul><li>Gateways </li></ul><ul><li>Bridges </li></ul><ul><li>firewall </li></ul>
  10. 10. History of computer network <ul><li>In 1969,a network called ARPANET (advanced research project agency) was created. For transmission lines of 56kb dedicated line. </li></ul><ul><li>In 1970, DECNET (digital electronic corporation network) was created . For proper trait design. </li></ul><ul><li>In 1977-83, ETHERNET was created . Network capacity10Mhz. Support token ring topology. </li></ul><ul><li>In 1981, a network called TCP/IP (transmission control protocol/internet protocol) was created. To support LAN and WAN. Which lead to the beginning of INTERNET. </li></ul><ul><li>In 1980’s , GIGA BYTE network was created. To support applications such as FTP, SMTP, HTTP, POP3, IMAP4. </li></ul>
  11. 11. NIC (network interface card) <ul><li>Also known as Lan card ,Ethernet card, Network/Ethernet adaptor. </li></ul><ul><li>It is an interface between computer and network cables. </li></ul><ul><li>Functions of LAN card are, </li></ul><ul><li>*Data transfer </li></ul><ul><li>*Buffering data construction </li></ul><ul><li>*Medium access control </li></ul><ul><li>*Encoding and decoding </li></ul><ul><li>*Data transmission and reception </li></ul><ul><li>Lan cards are full duplex ( they can send and receive data ) </li></ul><ul><li>Lan card can have UTP, BNC, AUI ports. </li></ul><ul><li>Lan card puts packet on the cable. </li></ul><ul><li>It contains MAC address. </li></ul>
  12. 12. What is MAC address? <ul><li>MAC (media access control ) 48-bit number (6-byte).Unique to each and every Lan card , represented in hexadecimal notation. </li></ul><ul><li>This address is used for communication at low level. </li></ul><ul><li>This address comes from manufacturer. </li></ul><ul><li>Securities are based on MAC address. </li></ul>
  13. 13. What is an IP? <ul><li>IP (Internet protocol) is a method or protocol by which data is sent from one computer to another computer on the internet. </li></ul><ul><li>Each computer on the internet has at least one IP address that uniquely identifies it from all other computer on the internet. </li></ul><ul><li>When you send or receive data ( for example , an e-mail or web page), the message gets divided into little chunks called packets. </li></ul><ul><li>Each of these packets contains both senders internet address (IP address) and the receivers address. </li></ul><ul><li>Any packet is sent first to gateway computer that understands a small part of internet. </li></ul>
  14. 14. <ul><li>The gateway computer reads the destination address and forwards the packet to an adjacent gateway that in turn read the destination address and so forth across the internet until one gateway recognizes the packet as belonging to computer within its immediate neighborhood or domain. </li></ul><ul><li>The gateway then forwards the packet directly to the computer whose address is specified. </li></ul><ul><li>Because message is divided into number of packets, each packet can, if necessary , be sent by a different route across the internet. </li></ul><ul><li>Packets can arrive in the different order they were sent in. </li></ul><ul><li>The internet protocol just delivers them. It is up to other protocol, the TCP/IP to put back in the right order. </li></ul>
  15. 15. What is IP address? <ul><li>An IP address is an address with which a computer is identified on a network (internet). </li></ul><ul><li>An IP address is a logical address of the network adaptor. </li></ul><ul><li>An IP address is a 32-bit number which has two parts network number and host number. </li></ul><ul><li>00001010000001110000010100000001 </li></ul><ul><li>Computer won’t have problem in understanding this number but we as human can’t deal with binary. </li></ul><ul><li>An organization named IANA (internationally assigned numbering authority) as divided this 32-bit number into 4-octat and has given the range from 0-255 </li></ul><ul><li>00001010- 00000111- 00000101- 00000001 </li></ul><ul><li>An IP address in represented in decimal notation form like, </li></ul><ul><li> </li></ul><ul><li>Based on the range from 0-255 IANA has divided this 32-bit number into three classes, </li></ul><ul><li>Class A from 0-126 </li></ul><ul><li>Class B from 128-191 </li></ul><ul><li>Class C from 192-223 </li></ul><ul><li>*127 is loopback address </li></ul><ul><li>*224-255 is for research and development purpose. </li></ul><ul><li>To manage and maintain network again IANA has divided each class of IP address into 2 parts, </li></ul><ul><li>*Network portion (N/P) –represented by 1’s </li></ul><ul><li>*Host portion (H/P)- by 0’s </li></ul><ul><li>IANA has assigned class A with single octet (8-bits) for network portion and three octet (24-bits) for host portion. </li></ul><ul><li>IANA has assigned class B with two octet (16-bits) for network portion and two octets (16-bits) for host portion. </li></ul><ul><li>IANA has assigned class C with three octet (24-bits) for network portion and single octet (8-bits) for host portion. </li></ul>
  16. 16. <ul><li>IANA has assigned class A with single octet (8-bits) for network portion and three octet (24-bits) for host portion. DSM (default subnet mask) : IANA has assigned class B with two octet (16-bits) for network portion and two octets (16-bits) for host portion. DSM (default subnet mask) : IANA has assigned class C with three octet (24-bits) for network portion and single octet (8-bits) for host portion. DSM (default subnet mask) : A subnet mask defines network portion of ip address and host portion of ip address.By knowing the subnet mask information, we can easily identify a particular machine ip belongs to which class. IP Address is dividedinto two types: 1. Private IP Address. 2. Public IP Address. Private ip address are basically used within the LAN environment.All private ip address are free to use you don't have to pay to any one for using these address.It is also known as Free IP Address. Private IP Address range: Class A  =  - Class B  = - Class C = - Public IP Address: Public ip address are used in WAN environment.Used for connection to internet.Public ip address are not free , you need to pay for ip address (to isp or iana). A part from above private ip address range from each and every class all the ip's are public ip's. </li></ul>
  17. 17. What is HUB? <ul><li>A HUB is a device which connects various machines in a network. It’s major function is to replicate data it receives from one device attached to it. Hub is &quot;Signal Splitter&quot; Operates in &quot;Physical Layer&quot; “Collisions” will occur in hub and it listen for collision domains. </li></ul>
  18. 18. <ul><li>  Hub is “ Half-duplex “(can receive or forward only) </li></ul><ul><li>  Also known as ” Concentrator” </li></ul><ul><li>   Types, </li></ul><ul><li>  Passive (splitter) </li></ul><ul><li>  Active (signal boosting) </li></ul><ul><li>  Intelligent (manageable) </li></ul>
  19. 19. What is a switch? <ul><li>A switch is a device which connects various systems in a network. </li></ul><ul><li>Switch maintains MAC address table . </li></ul><ul><li>Packets are directly transferred to the destination without broadcasting. </li></ul><ul><li>Switch is considered as an intelligent device . </li></ul><ul><li>In switch , each packet gets th same speed . </li></ul><ul><li>A switch is Full-duplex(can forward & receive simultanously) </li></ul><ul><li>Packets are filtered by switches. </li></ul><ul><li>No concept of collision domain or No collision as it is full duplex. </li></ul><ul><li>Works in “ Data link layer ” layer 2 and in layer 3 </li></ul><ul><li>There are two types of switches, </li></ul><ul><li>1. Managable switch –  has console port,we can make configuration </li></ul><ul><li>2. Unmanagable switch – has no console port. </li></ul>
  20. 20. <ul><li>Cisco divided switches in 3 layers: </li></ul><ul><li>1. Access layer switches : It works in layer 2 as it understands MAC address only.It doesn’t understand IP address.Switches series – 1900  &  2900 </li></ul><ul><li>2. Distribution layer and 3. Core layer switches : It works in layer 3 because it understands MAC address as well as IP address. Switches series – 7000 &  10000. </li></ul><ul><li>Distribution layer and core layer switches can access millions of packets per second  - whereas   - Router can access 1 lakh packets per second. </li></ul>
  21. 21. What is Router? <ul><li>A router is a device or a specialized computer which takes  data packets  from  incomming lines, and  decides  outgoing lines on which to forward them. </li></ul><ul><li>A router is responsible for routing the data packets towards their destination. </li></ul><ul><li>A router is a device, which enables communication between two different networks or enables communication between two different series/classes of network. </li></ul><ul><li>A router is a internetworking device. </li></ul><ul><li>A router routes the packet from one logical network to other logical network. </li></ul><ul><li>It deals with, finding the way to the destination. </li></ul>
  22. 22. <ul><li>The main job or function of router is to calculate the best path/route for the packet to reach to it’s destination.   or </li></ul><ul><li>The main role of router is to determine the best path towards destination. </li></ul><ul><li>It determines where the data should go on the physical network. </li></ul><ul><li>Types of Routers: </li></ul><ul><li>There are two types of routers: Fixed router and Modular router </li></ul><ul><li>Fixed router: </li></ul><ul><li>1. Parts in the router are inbuilt where modification to theinterface is not possible. </li></ul><ul><li>2. Access layer router are the  exmple of fixed router except 1600  and  1700 series. </li></ul><ul><li>Modular Router: </li></ul><ul><li>1. Parts to the router can be added and removed i.e modification to the interface is possible. </li></ul>
  23. 23. <ul><li>2. Distribution and core layer router are the examples of modular router. </li></ul><ul><li>Cisco Routers are divided into 3 catagories or layers: </li></ul><ul><li>1. Access Layer Router </li></ul><ul><li>2. Distribution Layer Router </li></ul><ul><li>3. Core Layer Router </li></ul><ul><li>Access Layer routers are used by small organizations.Also knownas desktop or company layer routers. Router that are mostly used here are,router series – 800, 1000, 1600, 1700, 2500. </li></ul><ul><li>Distribution Layer router are used by ISP’s .Also known as IS layer routers.Router series – 2600, 3200, 3600, 3700. </li></ul><ul><li>Core layer router are used by global ISP’s .Also known as backbone routers. Router series – 6400, 7200, 7300, 7400, 7500, 7600, 10000, 12000.  </li></ul>
  24. 24. What is repeater? <ul><li>Repeater is a device used to extend a network. </li></ul><ul><li>Extends the range of a network. </li></ul><ul><li>Amplifies or regenerates the data signal, in order to extend network. </li></ul><ul><li>Doesn’t amplify noise. </li></ul><ul><li>A repeater amplifies and cleans up digital signals and forwards their destination. </li></ul>
  25. 25. What is Modem? <ul><li>It is a device, which converts binary code (from the computer) to the analog signal needed for transmitting messages over telephone lines. </li></ul><ul><li>It does modulation-demodulation  </li></ul><ul><li>Or </li></ul><ul><li>A device used to convert digital signals into analog tones that can be transmitted over the telephone network.  </li></ul><ul><li>Types, </li></ul><ul><li>*Internal Modem </li></ul><ul><li>*External Modem </li></ul><ul><li>*Card Version </li></ul>
  26. 26. What is firewall? <ul><li>* System that establish access control policies among network. </li></ul><ul><li>* They can block information from entry. </li></ul><ul><li>* A combination of hardware and software that protects a network from attack by hackers that could gain access through public network, including the internet. </li></ul>
  27. 27. Different Types of Topologies <ul><li>* Star topology </li></ul><ul><li>* Bus topology </li></ul><ul><li>* Ring topology </li></ul><ul><li>* Token ring topology </li></ul><ul><li>* Hybrid topology </li></ul><ul><li>* Mesh topology </li></ul><ul><li>Topology means Structure of computer network or Design of computer network. </li></ul><ul><li>Star topology: </li></ul><ul><li>In star topology all the systems are connected to a central device which may be hub or switch. </li></ul><ul><li>Advantage: If one computer cable is broken or damage then other computers will not be affected i.e Network is not affected. </li></ul><ul><li>Diadvantage: If central device (hub or switch) stops working then whole company network is blocked (any system can’t communicate with each other). </li></ul>
  28. 28. <ul><li>Bus Topology: </li></ul><ul><li>In bus topology all the systems are connected to a single cable/channel or back bone .Computers are connected with this cable using BNC connector or T connector. At the both ends of cable Terminators are connected. </li></ul><ul><li>Advantage: Cheap  and Easy to implement. </li></ul><ul><li>Disadvantage: If terminators are not connected or open then data will bounce back. </li></ul><ul><li>Ring Topology: </li></ul><ul><li>In ring topology each computer is connected to each other .ie every system is connected   to their next system in form of ring . </li></ul><ul><li>Advantage: Easy to install and easy to troubleshoot. </li></ul><ul><li>Disadvantage: If one of the computer goes down or if one of the cable break between two machines then whole the network is down.Data packets can’t go further. </li></ul><ul><li>Token Ring Topology: </li></ul><ul><li>In token ring toplogy, all the systems are connected to a central device ”MSAU”  multiple station access unit Hub. </li></ul><ul><li>Token ring is 802.5 standard. </li></ul><ul><li>Developed by IBM </li></ul><ul><li>Has a unique token passing access method. </li></ul>
  29. 29. <ul><li>Contains an “electronic signal” which constantly rotates in MSAU hub. </li></ul><ul><li>Here if one computer needs to send a packet to other then this packet from source machine is taken or attached to token(electronic signal) and forwarded or takes to the destination address machine. </li></ul><ul><li>Disadvantage: If this central device (MSAU)  stops working or fails then whole the company network is down or all the systems connected can’t communicate with each other. </li></ul>
  30. 30. Gateways <ul><li>A system that bridges two systems. </li></ul><ul><li>A computer connected with various computer, wants to transfer a packet, can transfer directly to the router by giving router address as gateway address at IP address portion. </li></ul><ul><li>  Gateways are used to connect two dissimilar LAN . </li></ul><ul><li>Gateways work in application layer of OSI model. </li></ul><ul><li>A gateway is required to convert data packets from one protocol format to another before forwarding it, as it connects two dissimilar networks. </li></ul><ul><li>Gateway Protocols: </li></ul><ul><li>Members of  TCP/IP  protocol suite that routers use to determine the best route  for the data packets.   </li></ul>
  31. 31. Ethernet <ul><li>Originally developed by Xerox corporation, that can link upto 1024 nodes in bus network. </li></ul><ul><li>A networking hardware , communication and cabling standard. </li></ul><ul><li>A high-speed standard using a base band (single channel) communication technique. </li></ul><ul><li>Ethernet Provides row data transfer rate of 10 Mbps. </li></ul><ul><li>Ethernet uses (CSMA/CD) to prevent network failures when two devices try to access the network at the same time. </li></ul>
  32. 32. What is the architecture of networking? <ul><li>1. Peer to Peer (Point to Point): </li></ul><ul><li>Here each node acts as client as well as server. </li></ul><ul><li>Hard disk, cd-rom, printer can be shared. </li></ul><ul><li>Example: windows2000, 9x </li></ul><ul><li>Sharing of file between two nodes </li></ul><ul><li>Nobody is server here </li></ul><ul><li>Using desktop type of OS (XP) we can use peer to peer. </li></ul><ul><li>2. Client/ Server: </li></ul><ul><li>Best example, Internet. </li></ul><ul><li>It can support more than one processor. </li></ul><ul><li>Server- giving services, file sharing server, printing server. </li></ul><ul><li>Example: a demo video showing on server can be shared to all the machines in a network. </li></ul><ul><li>UNIX, windows, Linux dominates. </li></ul><ul><li>Used in large environment. </li></ul><ul><li>One or more machine as dedicated server. </li></ul>