Fundamental of Computer Network PDF

Fundamental of Computer Network  Computer Networks ⚫A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications. ⚫The computers on a network may be linked through cables...

Fundamental of Computer Network  Computer Networks ⚫A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications. ⚫The computers on a network may be linked through cables, telephone lines, radio waves, satellites etc. ⚫A popular example of a computer network is the Internet, which allows millions of users to share information. 2 Computer Network 3  Every Network Includes: 1. At least two computers that have something to share. 2. A cable or wireless pathway, called Transmission Media, for computers to signal each other. 3. Rules, called Protocols, so that computers can use the unified principle of data communication. 4. Networking Interface Cards (NIC) 4  Advantages of Computer Networks ⚫File Sharing: Networks offer a quick and easy way to share files directly. ⚫Resource Sharing: All computers in the network can share resources such as printers, fax machines, modems and scanners. ⚫Communication: Those on the network can communicate with each other via e-mail, instant messages etc. 5  Advantages of Computer Networks Flexible Access: Networks allow their users to access files from computers throughout the network. Sharing of Information: Computer networks enable us to share data and information with the computers that are located geographically large distance apart. 6  Network Computing Models Centralized Computing (Client-Server Network) A client-server network is where every client is connected to the server. Server or mainframe computer has huge storage and processing capabilities. 7 Network Computing Models Distributed Computing (Peer-to-Peer Network) All devices have same power. It interconnects one or more computers. Centralized backup is not possible. 8  Uses of Computer Network Simultaneous Access Shared Peripheral Devices Personal Communication Easier Backup 9  What is Ethernet? ⚫A group of standards for defining a local area network that includes standards in cabling and the structure of the data sent over those cables as well as the hardware that connects those cables. ⚫Independent of the network architecture. ⚫Flavors of Ethernet: IEEE 802.3 Ethernet Specification Great detail specifying cable types, data formats, and procedures for transferring that data through those cables IEEE 802.5 Token Ring Specification 10 APPLICATIONS OF NETWOKS ⚫E-mail ⚫Searchable Data (Web Sites) ⚫E-Commerce ⚫News Groups ⚫Internet Telephony (VoIP) ⚫Video Conferencing ⚫Chat Groups ⚫Instant Messengers ⚫Internet Radio 11  What is a Topology? Network topologies describe the ways in which the elements of a network are mapped. They describe the physical and logical arrangement of the network nodes. The physical topology of a network refers to the configuration of cables, computers, and other peripherals  Different Types of Topologies Bus Topology Star Topology Ring Topology Mesh Topology Tree Topology Hybrid Topology  Bus Topology All the nodes (file server, workstations, and peripherals) on a bus topology are connected by one single cable. A bus topology consists of a main run of cable with a terminator at each end. All nodes (file server, workstations, and peripherals) are connected to the linear cable. Popular on LANs because they are inexpensive and easy to install. Bus Topology  Bus Topology Advantages of Bus Topology It is Cheap, easy to handle and implement. Require less cable It is best suited for small networks. Disadvantages of Bus Topology The cable length is limited. This limits the number of stations that can be connected. This network topology can perform well only for a limited number of nodes.  Ring Topology In a ring network, every device has exactly two neighbours for communication purposes. All messages travel through a ring in the same direction. A failure in any cable or device breaks the loop and can take down the entire network. To implement a ring network we use the Token Ring technology A token, or small data packet, is continuously passed around the network. When a device needs to transmit, it reserves the token for the next trip around, then attaches its data packet to it. Ring Topology  Ring Topology Advantage of Ring Topology Very orderly network where every device has access to the token and the opportunity to transmit. Easier to Mange than a Bus Network Good Communication over long distances Handles high volume of traffic Disadvantages of Ring Topology The failure of a single node of the network can cause the entire network to fail. The movement or changes made to network nodes affects the performance of the entire network.  Star Topology In a star network, each node (file server, workstations, and peripherals) is connected to a central device called a hub. The hub takes a signal that comes from any node and passes it along to all the other nodes in the network. Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. The hub, switch, or concentrator manages and controls all functions of the network. The star topology reduces the chance of network failure by connecting all of the systems to a central node. Star Topology  Star Topology Advantages of Star Topology Easy to manage Easy to locate problems (cable/workstations) Easier to expand than a bus or ring topology. Easy to install and wire. Easy to detect faults and to remove parts. Disadvantages of Star Topology Requires more cable length than a linear topology. If the hub or concentrator fails, nodes attached are disabled. More expensive because of the cost of the concentrators.  Tree Topology A tree topology (hierarchical topology) can be viewed as a collection of star networks arranged in a hierarchy. This tree has individual peripheral nodes which are required to transmit to and receive from one other only and are not required to act as repeaters or regenerators. The tree topology arranges links and nodes into distinct hierarchies in order to allow greater control and easier troubleshooting. This is particularly helpful for colleges, universities and schools so that each of the connect to the big network in some way. Tree Topology  Tree Topology Advantages of a Tree Topology Point-to-point wiring for individual segments. Supported by several hardware and software vendors. All the computers have access to the larger and their immediate networks. Disadvantages of a Tree Topology Overall length of each segment is limited by the type of cabling used. If the backbone line breaks, the entire segment goes down. More difficult to configure and wire than other topologies.  Mesh Topology In this topology, each node is connected to every other node in the network. Implementing the mesh topology is expensive and difficult. In this type of network, each node may send message to destination through multiple paths. While the data is travelling on the Mesh Network it is automatically configured to reach the destination by taking the shortest route which means the least number of hops. Mesh Topology  Mesh Topology Advantage of Mesh Topology No traffic problem as there are dedicated links. It has multiple links, so if one route is blocked then other routes can be used for data communication. Points to point links make fault identification easy. Disadvantage of Mesh Topology There is mesh of wiring which can be difficult to manage. Installation is complex as each node is connected to every node. Cabling cost is high.  Hybrid Topology A combination of any two or more network topologies. A hybrid topology always accrues when two different basic network topologies are connected. It is a mixture of above mentioned topologies. Usually, a central computer is attached with sub-controllers which in turn participate in a variety of topologies Hybrid Topology  Hybrid Topology Advantages of a Hybrid Topology It is extremely flexible. It is very reliable. Disadvantages of a Hybrid Topology Expensive What is Networking Hardware? Networking hardware includes all computers, peripherals, interface cards and other equipment needed to perform data- processing and communications within the network. 32  Networking Hardware Network Interface Card Hub Repeater Bridge Switch Gateway 33  Network Interface Cards Network interface cards, commonly referred to as NICs, are used to connect a PC to a network. The NIC provides a physical connection between the networking cable and the computer's internal bus. Different computers have different bus architectures; PCI bus master slots are most commonly found on 486/Pentium PCs and ISA expansion slots are commonly found on 386 and older PCs. NICs come in three basic varieties: 8-bit, 16-bit, and 32-bit. The larger the number of bits that can be transferred to the NIC, the faster the NIC can transfer data to the network cable. 34 Network Interface Cards 35  Hubs A hub joins multiple computers (or other network devices) together to form a single network. On this network, all computers can communicate directly with each other. The networking hub is a junction box with several ports in the back for receiving the Ethernet cables that are plugged into each computer on the LAN. 36  Types of Hubs A passive hub serves simply as a passage for the data, enabling it to go from one device to another. Intelligent hub include additional features that enables an administrator to monitor the traffic passing through the hub and to configure each port in the hub. Switching hub, actually reads the destination address of each packet and then forwards the packet to the correct port. 37 Hubs 38  Repeater Since a signal loses strength as it passes along a cable, it is often necessary to boost the signal with a device called a repeater. A repeater is an electronic device that receives a signal, cleans it of unnecessary noise, regenerates it, and retransmits it at a higher power level so that the signal can cover longer distances without degradation. A good example of the use of repeaters would be in a local area network using a star topology with unshielded twisted- pair cabling. 39 Repeaters 40  Switch A network switch is a small hardware device that joins multiple computers together within one local area network (LAN). Network switches appear nearly identical to network hubs, but a switch generally contains more intelligence than a hub. Unlike hubs, network switches are capable of inspecting data packets as they are received, determining the source and destination device of each packet, and forwarding them appropriately. Allow several users to send information over a network at the same time without slowing each other down. 41 Switch 42  Router A device to interconnect SIMILAR networks, e.g. similar protocols and workstations and servers. A router is an electronic device that interconnects two or more computer networks, and selectively interchanges packets of data between them. Each data packet contains address information that a router can use to determine if the source and destination are on the same network, or if the data packet must be transferred from one network to another. 43 Router 44  Bridge A bridge is a device that connects a local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or token ring). The function of a bridge is to connect separate networks together. Bridges connect different networks types (such as Ethernet and Fast Ethernet) or networks of the same type. Bridges map the Ethernet addresses of the nodes residing on each network segment and allow only necessary traffic to pass through the bridge. When a packet is received by the bridge, the bridge determines the destination and source segments. 45  Types of Bridges Bridges come in three basic types: Local bridges: Directly connect local area networks (LANs) Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges have been replaced with routers. Wireless bridges: Can be used to join LANs or connect remote stations to LANs. 46 Bridges 47  Gateway Gateways are used to interconnect two different networks having different protocols. Networks using different protocols use different addressing formats. A gateway is a network point that acts as an entrance to another network. Gateways are also called protocol converters. 48 Gateway 49  What is the difference? Bridge: device to interconnect two LANs that use the SAME logical link control protocol but may use different medium access control protocols. Router: device to interconnect SIMILAR networks, e.g. similar protocols and workstations and servers. Gateway: device to interconnect DISSIMILAR protocols and servers, and Macintosh and IBM LANs and equipment 50