Computer Networking Lecture Notes PDF

Computer Networking Dr. Enas Elgeldawi Lecture Outline  What is a Computer Network?  Objectives of Networks  Uses of Computer Networks  Network Types: LAN – MAN – WAN  Network Topology  Casting  Transmission Modes What is a Computer Network? A computer network is simply two or more...

Computer Networking Dr. Enas Elgeldawi Lecture Outline  What is a Computer Network?  Objectives of Networks  Uses of Computer Networks  Network Types: LAN – MAN – WAN  Network Topology  Casting  Transmission Modes What is a Computer Network? A computer network is simply two or more computing devices connected together in a way that lets them exchange information and share resources (such as hard drives, CD-Roms, fax-modems, printers, etc.). The connection can be via a copper wire, telephone lines, lasers, radio waves, earth satellites, or infrared light beams. Objectives of Networks Some of the common objectives of computer networks are:  To provide sharing of (distant) resources such as information (databases) or processors (CPUs).  To provide interprocess communication, such as among users and processors. Network users, located geographically apart, may converse in an interactive session through the network.  To provide high reliability by having alternative sources of supply. If one processor breaks down, another processor in the network can take its place. Similarly, if one link on a route fails, another route becomes available. Objectives of Networks  To provide distribution of processing functions. For example, a transaction is translated in one node, processed in another, and the response formatted in a third one. Distributed processing primarily implies taking processing out of a single, large computer and distributing it to where the raw information is generated or most of the transaction handling, calculation, or formatting is performed.  To furnish centralized control for a geographically distributed system, such as inventory management in the manufacturing industry, and handling accounts in the finance industry. Defense networks may provide central control facilities for geographically distributed monitoring stations. Uses of Computer Networks Some examples of possible uses for computer networks:  A software firm that has produced a valuable program may allow their clients to log in over the network and run the program. This is especially when the program is large, machine dependent, or embedded in a web of libraries, and other non-portable environmental features.  Computer networks become hugely important to people who are geographically challenged, giving them the same access to services as people living in the middle of a big city. Universities may go national or international. Telemedicine (i.e., remote patient monitoring).  Doing business with customers over the network. Airlines, book stores and music vendors have discovered that many customers like the convenience of shopping at home. Consequently, many companies provide catalogs of their goods and services online and take orders on-line. This is called e-commerce (electronic commerce).  Another area in which e-commerce is growing is access to financial institutions. Many people already pay their bills, manage their bank accounts, and handle their investments electronically.  Many newspapers have gone on-line and can personalized. For example, it is possible to tell the newspaper that you want everything about a certain topic, have the selected article downloaded to your hard disk or printed on your computer.  The next step beyond newspapers is the on-line digital library. Many educational and professional organizations have many books, journals, and conference proceedings on-line.  Electronic mail or email is already widely used by millions of people and it contains audio and video as well as text.  Another form of computer-assisted communication is videoconferencing. Using this technology, people at distant location can hold a meeting, seeing and hearing each other and even writing on a shared virtual blackboard. Videoconferencing is a powerful tool for eliminating the cost and time previously devoted to travel. Network Types: LAN – MAN - WAN LAN LAN is a Local Area Network. As name suggests LANs are basically used to connect a limited geographical area: for example, when we want to use network at home, a school, an office, at college, etc. Computers placed in this limited area are linked together. LANs can span over a limited range i.e. of 1 km in radius. Communication is carried out from one computer to another, and there is no need of any central computer, and each computer has the same role. The smallest LAN can consist of 2 computers. And maximum can consist of many more computers. LANs are usually owned, controlled, and managed by a single person or any organization. Many devices such as; routers, Ethernet switches, hubs, repeaters, and bridges are used for LAN. Full-time connectivity is provided to local service and multi-access is allowed to high-bandwidth media. This network lets users to communicate, transfer files, etc. LAN can be connected to other LANs or WANs. WAN WAN is a Wide Area Network, WANs are typically used to connect comparatively large geographical area such as; a state, a country, a continent, the Internet. WANs can span over a range of huge area of 100,000 kilometer radius (between the Earth and artificial satellites). WANs have its ownership and management is distributed it cannot be handled at individual level. A few common devices that are used in WANs are: routers, communication servers, and modems. WANs provide you a full-time network and part- time network as well for connectivity and allow access over interfaces which are operating at lower speeds. WANs are used to connect LANs and provide access to computers or file servers outside of their area. In WAN, communication, sharing of files, etc is possible over larges distances. MAN MAN is Metropolitan Area Network and is used to connect two or more LANs in a common geographic area: say a city or a group of buildings. MANs can span in the range of 5 to 50 kilometers in diameter. MANs usually are not owned by a single organization, they are owned by an association of users or by a single network provider who sells the service to the users. MAN can be considered as a larger version of a LAN which allows users to share resources at a greater span of distance as compared to LAN. Distance Location Network Used 10 meters Classroom LAN 100 meters Building LAN 1000 meters Campus LAN 10 kilometers City MAN 100 kilometers County WAN 1,000 kilometers Continent WAN 10,000 kilometers Planet – Internet WAN Network Topology A network configuration is also called a network topology. A network topology is the shape or physical connectivity of the network. The network designer has three major goals when establishing the topology of a network:  Provide the maximum possible reliability: provide alternative routes if a node fails and be able to pinpoint the fault readily, deliver user data correctly and recover from errors or lost data in the network.  Route network traffic through the least cost path within the network: minimizing the actual length of the channel between the components and providing the least expensive channel option for a particular application.  Give the end users the best possible response time and throughput. Bus Topology In a bus topology each node (computer, server, peripheral, etc.) attaches directly to a common cable. This topology most often serves as the backbone for a network. In some instances, such as in classrooms or labs, a bus will connect small workgroups. At any instant one machine is the master and is allowed to transmit. All other machines are required to refrain from sending. An arbitration mechanism is needed to resolve conflicts when two or more machines want to transmit simultaneously. This topology's wiring scheme is unstructured making it difficult to troubleshoot. Often if one PC goes down, the whole network can shut down. Ring topology Nodes are connected in a circular pattern, and packets of information are sent through the ring until they reach their destination. Ring networks can outperform those based on the bus topology, and they can be easily reconfigured to add or remove devices. However, they are still relatively vulnerable, since the whole network fails if a single node fails. Also, bandwidth must be shared across all the devices and connections. Star Topology A star topology, on the other hand, is relatively easy to troubleshoot due to its structured wiring scheme. With this topology, each node has a dedicated set of wires connecting it to a central network hub. A hub is a common wiring point used to connect multiple cable runs in a star-wired topology network into a single network. Hubs have multiple ports to attach the different cable runs. The failure of one connection will not usually affect the others. And, since all traffic passes through the hub, the hub becomes a central point for isolating network problems and gathering network statistics. The star topology can have a number of different transmission mechanisms, depending on the nature of the central hub. Star networks are easy to modify and one can add new nodes without disturbing the rest of the network. Intelligent hubs provide for central monitoring and managing. Often there are facilities to use several different cable types with hubs. Central hub failure will lead to total network failure. They are also costly to cable since all network cables must be pulled to one central point. Mesh topology There are two types of mesh topology. In the first, which is called full mesh topology, each node is directly connected to every other node. In a partial mesh topology, nodes are only connected to the nodes they interact with most. Most networks employ some combination of topologies to yield what’s called a hybrid topology. For instance, the tree topology combines the bus and mesh topologies. Casting Casting in Computer Networks means transmitting data from the source to the recipient(s) over a communication channel. There are three different types of casting in computer networks, which are:  Unicast transmission  Broadcast transmission  Multicast transmission The key difference is in data delivery: Unicast sends data to a single recipient, Broadcast sends data to all devices in a network, and Multicast sends data to a specific group of subscribed devices. Unicast (One-to-One) Multicast (One-to-Many) Broadcast (One-to-All) Limited Broadcast Limited Broadcast Direct Broadcast Transmission Modes Simplex Simplex communication is a one-way communication system where information is transmitted from one device to another, but the receiving device cannot send information back to the transmitting device. In other words, simplex communication is a unidirectional form of communication, where the communication is one-way only. Examples of Simplex: Television, Radio Broadcasts Transmission Modes Half-Duplex Half-duplex communication is a communication system that allows for two-way communication between two or more parties, but only one party can transmit data at a time. Half-duplex communication enables both parties to send and receive information, but not at the same time. Examples of Half-Duplex: walkie-talkie Transmission Modes Half-Duplex Full-duplex communication is a communication system that allows for two-way communication between two or more parties, where each party can send and receive information simultaneously. In other words, full-duplex communication enables multiple parties to communicate in real-time, with the ability to send and receive data at the same time. Examples of Half-Duplex: speaking on a mobile phone call, video conferencing and online gaming.