PracticalFile of Computer Networks Submitted To: Mr. Harikesh Submitted By: Dharmender(4352), Nitin(4354), Gaurav Yadav (4363), Vipin Kumar, Pankaj, Krishan Lohiya(4356) Introduction To Computer Networks Today the world scenario is changing. Data Communication and network have changed the way business and other daily affair works. Now, they rely on computer networks and internetwork. A set of devices often mentioned as nodes connected by media link is called a Network. A node can be a device which is capable of sending or receiving data generated by other nodes on the network like a computer, printer etc. These links connecting the devices are called Communication channels. Computer network is a telecommunication channel through which we can share our data. It is also called data network. The best example of computer network is Internet. Computer network does not mean a system with control unit and other systems as its slave. It is called a distributed system A network must be able to meet certain criteria, these are mentioned below: 1. Performance 2. Reliability Properties of Good Network 1. Interpersonal Communication : We can communicate with each other efficiently and easily example emails, chat rooms, video conferencing etc. 3. We can use different types of topologies through LAN. Types of Communication Networks Local Area Network (LAN) It is also called LAN and designed for small physical areas such as an office. Resources can be shared : We can use the resources provided by network such as printers etc. these are Star.2. to share files and network among each other while it can also be as complex as interconnecting an entire building. Bus. LANs are used widely as it is easy to design and to troubleshoot. group of buildings or a factory. Ring. . data : Authorised users are allowed to share the files on the network. Tree etc. Personal computers and workstations are connected to each other through LANs. Sharing files. LAN can be a simple network like connecting two computers. It is also called MAN and uses the similar technology as LAN. It can be means to connecting a number of LANs into a larger network or it can be a single cable.LAN networks are also widely used to share resources like printers. It is mainly hold and operated by single private company or a public company. It is designed to extend over the entire city. . shared hard-drive etc. Metropolitan Area Network (MAN) It is basically a bigger version of LAN. WAN can be private or it can be public leased network..Wide Area Network (WAN) It is also called WAN. We can access Internet at any place avoiding wire related troubles. . It is used for the network that covers large distance such as cover states of a country. These can be used also when the telephone systems gets destroyed due to some calamity/disaster. They are becoming very important in our daily life because wind connections are not possible in cars or Aeroplane. Wireless Network It is the fastest growing segment of computer. It is not easy to design and maintain. WANs are really important now-a-days. WAN operates on low data rates. Communication medium used by WAN are PSTN or Satellite links. We can join two or more individual networks to form an internetwork through devices like routers gateways or bridges.Inter Network When we connect two or more networks then they are called internetwork or internet. . 3. 4. It is easy to understand.Types of Network Topology Network Topology is the schematic description of a network arrangement. BUS Topology Bus topology is a network type in where every computer and network device is connected to single cable. Features of Bus Topology 1. Easy to expand joining two cables together. 2. Cable required is least compared to other network topology. It is cost effective. Every device is connected to a single cable Advantages of Bus Topology 1. Used in small networks. 2. Disadvantages of Bus Topology . 5. connecting various nodes(sender and receiver) through lines of connection. It transmits data only in one direction. 3. Exactly two neighbours for each device. If network traffic is heavy or nodes are more the performance of the network decreases. 2. 2. RING Topology It is called ring topology because it forms a ring as each computer is connected to another computer. . A number of repeaters are used and the transmission is unidirectional. Date is transferred in a sequential manner that is bit by bit. with the last one connected to the first. It is slower than the ring topology. Features of Ring Topology 1. Cables fails then whole network fails. 4.1. Cable has a limited length. STAR Topology In this type of topology all the computers are connected to a single hub through a cable. Adding or deleting the computers disturbs the network activity.Advantages of Ring Topology 1. 2. as only the nodes having tokens can transmit data. 3. This hub is the central node and all others nodes are connected to the central node. Acts as a repeater for data flow. Cheap to install and expand Disadvantages of Ring Topology 1. 2. Can be used with twisted pair. Advantages of Star Topology . Transmitting network is not affected by high traffic or by adding more nodes. Failure of one computer disturbs the whole network. Troubleshooting is difficult in ring topology. Features of Star Topology 1. Optical Fibre or coaxial cable. 3. Every node has its own dedicated connection to the hub. 2. Performance is based on the hub that is it depends on its capacity MESH Topology It is a point-to-point connection to other nodes or devices. If the hub is affected then the whole network is stopped because all the nodes depend on the hub. Easy to troubleshoot. Disadvantages of Star Topology 1. Types of Mesh Topology . Only that node is affected which has failed rest of the nodes can work smoothly. Traffic is carried only between two devices or nodes to which it is connected. Mesh has n (n-2)/2 physical channels to link hn devices. 5. Hub can be upgraded easily. Easy to setup and modify. Expensive to use. Fast performance with few nodes and low network traffic. 2. 2. 3. Cost of installation is high. 3. 4.1. 4. Central hub fails. Bulk wiring is required. Advantages of Mesh Topology 1. 3.1. Disadvantages of Mesh Topology 1. Partial Mesh Topology : In this topology some of the systems are connected in the same fashion as mesh topology but some devices are only connected to two or three devices. Provides security and privacy. Fault is diagnosed easily. 4. 2. Features of Mesh Topology 1. 2. network fails. 1. 3. 3. Fully connected. Each connection can carry its own data load. HYBRID Topology . 2. Not flexible. Robust. Installation and configuration is difficult. Full Mesh Topology : Each and every nodes or devices are connected to each other. 2. Cabling cost is more. It is robust. Flexible. Complex in design. For example if in an office in one department ring topology is used and in another star topology is used. 4. connecting these topologies will result in Hybrid Topology (ring topology and star topology). Inherits the advantages and disadvantages of the topologies included Advantages of Hybrid Topology 1. Disadvantages of Hybrid Topology 1. It is a combination of two or topologies 2. Reliable as Error detecting and trouble shooting is easy. 3. 2. Scalable as size can be increased easily. Effective. . Features of Hybrid Topology 1.It is two different types of topologies which is a mixture of two or more topologies. Costly.2. Transmission Mediums in Computer Networks . The first layer (physical layer) of Communication Networks OSI Seven layer model is dedicated to the transmission media. The types of Bounded/ Guided are discussed below. ultraviolet light. Electromagnetic energy (includes electrical and magnetic fields) includes power.Data is represented by computers and other telecommunication devices using signals. visible light. gamma rays etc. Electromagnetic signals travel through vacuum. Signals are transmitted in the form of electromagnetic energy from one device to another. radio waves. voice. we will study the OSI Model later. air or other transmission mediums to travel between one point to another(from source to receiver). . Transmission medium is the means through which we send our data from one place to another. Bounded/Guided Transmission Media It is the transmission media in which signals are confined to a specific path using wire or cable. Cable with 2 pair use RJ-11 connector and 4 pair cable useRJ-45 connector. It is lightweight.2 dB/Km @ 1kHz. can be installed easily. UTP cables consist of 2 or 4 pairs of twisted cable. each with its own colour plastic insulator. cheap. Some important points : Its frequency range is 0 to 3. Typical delay is 50 µs/km. Identification is the reason behind coloured plastic insulation. and they support many different types of network.5 kHz. Repeater spacing is 2km. Typical attenuation is 0. Twisted Pair is of two types : Unshielded Twisted Pair (UTP) Shielded Twisted Pair (STP) Unshielded Twisted Pair Cable It is the most common type of telecommunication when compared with Shielded Twisted Pair Cable which consists of two conductors usually copper. . Twisted Pair Cable This cable is the most commonly used and is cheaper than others. The wires are twisted together in a helical form to reduce electrical interference from similar pair. 100 meter limit Higher grades of UTP are used in LAN technologies like Ethernet. Disadvantages : Bandwidth is low when compared with Coaxial Cable Provides less protection from interference. It consists of two insulating copper wires (1mm thick). Shielded Twisted Pair Cable .Advantages : Installation is easy Flexible Cheap It has high speed capacity. Electromagnetic noise penetration is prevented by metal casing.This cable has a metal foil or braided-mesh covering which encases each pair of insulated conductors. It is faster the unshielded and coaxial cable. It is more expensive than coaxial and unshielded twisted pair. It has same attenuation as unshielded twisted pair. Shielding also eliminates crosstalk (explained in KEY TERMS Chapter). Advantages : Easy to install Performance is adequate Can be used for Analog or Digital transmission Increases the signalling rate Higher capacity than unshielded twisted pair Eliminates crosstalk Disadvantages : Difficult to manufacture Heavy . The outermost part is the plastic cover which protects the whole cable. Coaxial Cable Coaxial is called by this name because it contains two conductors that are parallel to each other. It is surrounded by PVC installation. 50-Ohm RG-7 or RG-11 : used with thick Ethernet. The outer conductor is also encased in an insulating sheath. There are two types of Coaxial cables : . 50-Ohm RG-58 : used with thin Ethernet 75-Ohm RG-59 : used with cable television 93-Ohm RG-62 : used with ARCNET. a sheath which is encased in an outer conductor of metal foil. barid or both. Here the most common coaxial standards. Outer metallic wrapping is used as a shield against noise and as the second conductor which completes the circuit. Copper is used in this as centre conductor which can be a solid wire or a standard one. Baseband transmits a single signal at a time with very high speed. The major drawback is that it needs amplification after every 1000 feet. Fiber Optic Cable . The can span to longer distance at higher speeds as they have better shielding when compared to twisted pair cable Disadvantages : Single cable failure can fail the entire network. Difficult to install and expensive when compared with twisted pair. BroadBand This uses analog transmission on standard cable television cabling. It transmits several simultaneous signal using different frequencies. Transmits digital signals at a very high rate of 10Mbps. Much higher noise immunity Data transmission without distortion. If the shield is imperfect. it can lead to grounded loop. It covers large area when compared with Baseband Coaxial Cable. Advantages : Bandwidth is high Used in long distance telephone lines. It is mostly used for LAN’s. BaseBand This is a 50 ohm (Ω) coaxial cable which is used for digital transmission. The core in fiber optic cable is surrounded by glass cladding with lower index of refraction as compared to core to keep all the light in core.These are similar to coaxial cable. Fiber optic cable has bandwidth more than 2 gbps (Gigabytes per Second) Advantages : Provides high quality transmission of signals at very high speed. In multimode fibres. The fibers are grouped together in bundles protected by an outer shield. This is covered with a thin plastic jacket to protect the cladding. At the centre is the glass core through which light propagates. It uses electric signals to transmit data. and In single mode fibres. . Disadvantages : It is expensive Difficult to install. so noise and distortion is very less. Used for both analog and digital signals. the thickness is 8 to 10 microns. Do not allow complete routing of light signals. These are not affected by electromagnetic interference. Maintenance is expensive and difficult. the core is 50microns. It operates in a system with a low gigahertz range. which is available to anyone who has a device capable of receiving them. but below space. Types of unguided/ unbounded media are discussed below : Radio Transmission MicroWave Transmission Radio Transmission Its frequency is between 10 kHz to 1GHz. It is mostly used for unicast communication. It is simple to install and has high attenuation. These waves are used for multicast communications. Ionosphere : The layer of the atmosphere above troposphere. Microwave Transmission It travels at high frequency than the radio waves.UnBounded/UnGuided Transmission Media Unguided or wireless media sends the data through air (or water). Advantages of Microwave Transmission Used for long distance telephone communication . Types of Propogation Radio Transmission utilizes different types of propogation : Troposphere : The lowest portion of earth’s atmosphere extending outward approximately 30 miles from the earth’s surface. wind is found here. jet planes. Clouds. Contains electrically charged particles. It requires the sender to be inside of the receiver. A router can be used on any size of network. cabling or radio technology. A LAN requires a hub. network cards. Carries 1000’s of voice channels at the same time Disadvantages of Microwave Transmission It is Very costly Computer Network Devices Network devices are components used to connect computers or other electronic devices together so that they can share files or resources like printers or fax machines. Devices used to setup a Local Area Network (LAN) are the most common types of network devices used by the public. and if online access is desired. . This is much less complicated than it might sound to someone new to networking. router. Routers A router is a communications device that connects multiple computers or other routers togehter and transmits data to its correct destination on the network. a high-speed modem. On the largest scale. routers along the Internet backbone forward data packets to their destination using the fastest available path. which all the network equipment in your home can use. Modems A modem links your home entwork to the Internet through your Internet Service Provider (ISP). The high speed types o data outside o your home arn’t suitable or your direct use. . so modems convert the data into digital Ethernet. Repeaters require a small amount o time to regenerate the signal. When talking about. It retimes and regenerates the signals to proper amplitudes and sends them to other segments. Switch A switch or network switch is a small hardware device that joins multiple computers togethern within one Local Area Network (LAN). determining the source and destination device of each packet. and forwarding them appropriately. network switches are capable of inspecting data packets as they are received. This can cause a propagation delay which can affect network communication when there are several repeaters in a row. a network switch conserves network bandwidth and offers generally better performance than a hub. network switches operate at layer two (Data Link Layer) o the OSI Model. Technically. . Repeater A repeater connects two segments of your network cable. Unlike hubs. By delivering messages only to the connected device intended. you are probably talking about using a hub as a repeater. ethernet topology. Network switches appear nearly identical to network hubs. but a switch generally contains more intelligence (and a slightly higher price tag) than a hub. . Without this numeric protocol. If you're curious about your own IP address. Therefore an Internet Protocol address is part of the systematically laid out interconnected grid that governs online communication by identifying both initiating devices and various Internet destinations. An IP address consists of four numbers. sending and receiving data over the World Wide Web would be impossible.) separating each number or set of digits. so an IP address is an Internet Protocol address. country. Static IP addresses reveal such information as the continent.0. Static IP addresses never change. Many websites provide IP address look-up services to their visitors. and city in which a computer is located. Each of the four numbers can range from 0 to 255. region. as well as our requests for data and the data we've requested. thereby making two-way communication possible. ensuring that our messages.209. will reach their correct Internet destinations. free of charge. you can locate these websites by performing a Google search. as well as the locale. and such technical information as the precise latitude and longitude of the country. the ISP (Internet Service Provider) that services that particular computer. each of which contains one to three digits. IP addresses can be either static or dynamic. .125. with a single dot (. This innocuous-looking group of four numbers is the key that empowers you and me to send and retrieve data over our Internet connections.IP Address basics "IP" stands for Internet Protocol. Here's an example of what an IP address might look like: 78. What does that mean? An Internet Protocol is a set of rules that govern Internet activity and facilitate completion of a variety of actions on the World Wide Web. They serve as a permanent Internet address and provide a simple and reliable way for remote computers to contact you. of the computer. This often entails an extra charge. Easy access can also be facilitated when using a dynamic IP address through the use of a dynamic DNS service. online gaming. however. They are. which enables other computers to find you even though you may be using a temporary. Static IP addresses are generally preferable for such uses as VOIP (Voice over Internet Protocol). many ISPs reserve a portion of their assigned addresses for sharing among their subscribers in this way. so check with your ISP. Since a limited number of static IP addresses are available. one-time IP address. . This lowers costs and allows them to service far more subscribers than they otherwise could. or any other purpose where users need to make it easy for other computers to locate and connect to them. borrowed from a pool of IP addresses that are shared among various computers. Dynamic IP addresses are temporary and are assigned each time a computer accesses the Internet. in effect. There is not even a man page for this program. you get an ICMP packet back. traceroute displays each host that a packet travels through as it tries to reach its destination.Some commonly used Networking Commands Ping ping(8) sends an ICMP ECHO_REQUEST packet to the specified host. . If the host responds. host host(1) can do this for us. host is used to map names to IP addresses. traceroute / tracert / tracepath Slackware's traceroute(8) command is a very useful network diagnostic tool. You give finger a username or an email address and it will try to contact the necessary server and retrieve the username. Sound strange? Well. It is a very quick and simple utility without a lot of functions. nslookup has been deprecated and may be removed from future releases. telephone number. office. finger finger(1) will retrieve information about the specified user. and other pieces of information. you can “ping” an IP address to see if a machine is alive. nslookup nslookup is a tried and true program that has weathered the ages. just as if you were sitting at the terminal. This command displays incoming and outgoing network connections as well as other network information. netstat netstat stands for network statistics. Once your username and password are verified. ipconfig The ipconfig command is used on Windows. move files around. and other Unix-like operating systems. If you are running X and you telnet to another machine. Compose email. Mac. telnet allows you to log in to a computer. . and so on. you can run X programs on the remote computer and display them on yours. you can do anything requiring a text console. The ability to remotely log in and do stuff on another computer is what separates Unix and Unix-like operating systems from other operating systems. From here. read newsgroups. It’s available on Windows. Mac OS X. and Linux — each version has its own command-line options you can tweak to see different types of information. while the ifconfig command is used on Linux. you are given a shell prompt. These commands allow you to configure your network interfaces and view information about them. telnet Someone once stated that telnet(1) was the coolest thing he had ever 0seen on computers.