Computer Network


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Introduction to Networking
Network Configuration
Network Criteria
Transmission Mode
Network Topology

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Computer Network

  1. 1. MTN 2013Computer Network Technology Chapter 2 Computer Network
  2. 2. Outline1. Introduction to Networking2. Network Configuration3. Network Criteria4. Transmission Mode5. Network Topology11/17/2011 MTN 2013 2
  3. 3. 1. Introduction to Networking• What is network?• A network consists of 2 or more computers connected together, and they can communicate and share resources (i.e. information)11/17/2011 MTN 2013 3
  4. 4. Why Networking?• Sharing information — i.e. data communicationDo you prefer these? Or this?11/17/2011 MTN 2013 4
  5. 5. Networking• Sharing hardware or software • E.g. print document • Centralize administration and support • E.g. Internet-based, so everyone can access the same administrative or support application from their PCs11/17/2011 MTN 2013 5
  6. 6. How many kinds of Networks?• Depending on one’s perspective, we can classify networks in different ways • Based on transmission media: Wired (UTP, coaxial cables, fiber-optic cables) and Wireless • Based on network size: LAN and WAN (and MAN) • Based on management method: Peer-to-peer and Client/Server • Based on topology (connectivity): Bus, Star, Ring … : :11/17/2011 MTN 2013 6
  7. 7. 2. Network Configuration• Form/arrangement/setup of network parts/elements.• Ways that computers can be connected together to form networks.11/17/2011 MTN 2013 7
  8. 8. 3. Network Criteria• To be considered effective and efficient, a network must meet a number of criteria. The most important of these are performance, reliability, and security. Performance Reliability Security Type of Hardware Software connection Type of Frequency of Catastrophe transmission failure Number of user11/17/2011 MTN 2013 8
  9. 9. Performance• Performance can be measured in many ways, including transit time and response time.• Transit time is the amount of time required for a message to travel from one device to another.• Response time is the elapsed time between an enquiry and a response.• The performance of a network depends on a number of factors, including the number of users, the type of transmission medium, the capabilities of the connected hardware, and the efficiency of the software.11/17/2011 MTN 2013 9
  10. 10. Number of User• Having a large number of concurrent users can slow response time in a network not designed to coordinate heavy traffic loads.• The design of a given network is based on an assessment of the average number of users that will be communicating at any one time.• In peak load periods, however, the actual number of users can exceed the average and thereby decrease performance.• How a network responds to loading is measure of its performance.11/17/2011 MTN 2013 10
  11. 11. Type of Connection – Point to Point - single transmitter and receiver – Multipoint - multiple recipients of single transmission11/17/2011 MTN 2013 11
  12. 12. Type of Transmission• Unicast, multicast, broadcast• Transmission medium – The medium defines the speed at which data can travel through a connection. Today’s networks are moving to faster and faster transmission media, such as fiber-optic cabling, a medium that can carry data at only 10 megabits per second. However, the speed of light imposes an upper bound on the data rate.11/17/2011 MTN 2013 12
  13. 13. Hardware• The types of hardware included in a network affect both the speed and capacity of transmission. A higher-speed computer with greater storage capacity provides better performance.11/17/2011 MTN 2013 13
  14. 14. Software• The software used to process data at the sender, receiver, and intermediate nodes also affects network performance.• Moving a message from node to node through a network requires processing to transform the raw data into transmittable signals, to route these signals to the proper destination, to ensure error-free delivery, and to recast the signals into a form the receiver can use.• The software that provides these services affects both the speed and the reliability of a network link.• Well-designed software can speed the process and make transmission more effective and efficient.11/17/2011 MTN 2013 14
  15. 15. Reliability• In addition to accuracy of delivery, network reliability is measured frequency of failure, the time it takes a link to recover from a failure, and the network’s robustness in a catastrophe.11/17/2011 MTN 2013 15
  16. 16. Frequency of Failure• All networks fail occasionally.• A network that fails often, however, is of little value to a user.• Recovery time of a network after a failure: How long does it take to restore service? A network that recovers quickly is more useful than one that does not.11/17/2011 MTN 2013 16
  17. 17. Catastrophe• Networks must be protected from catastrophic events such as fire, earthquake, or theft.• One protection against unforeseen damage is a reliable system to back up network software.11/17/2011 MTN 2013 17
  18. 18. Security• Network security issues include protecting data from unauthorized access and viruses. Unauthorized access: For a network to be useful, sensitive data must be protected from unauthorized access. Protection can be accomplished at a number of levels. At the lowest level are user identification codes and passwords. At a higher level are encryption techniques. In these mechanisms, data are systematically altered in such a way that if an unauthorized user intercepts them, they will be unintelligible. Viruses: Because a network is accessible from many points, it can be susceptible to computer viruses. A virus is an illicitly introduced code that damages the system. A good network is protected from viruses by hardware and software designed specifically for that purpose.11/17/2011 MTN 2013 18
  19. 19. 4. Transmission Mode• Defines the direction of data flow between two linked devices.• The manner or way in which data is transmitted from one place to another is called data transmission mode.• There are three ways for transmitting data from one location to another. These are: – Simplex – Half duplex – Full duplex11/17/2011 MTN 2013 19
  20. 20. Simplex Mode• The communication can take place in only one direction.• A terminal can only send data and cannot receive it or it can only receive data but cannot send it.• It means that in this mode communication is uni-directional.• Today, this mode of data communication is not popular, because most of the modem communications require two-way exchange of data.• However, this mode of communication is used in business field at certain point-of-sale terminals in which sales data is entered without a corresponding reply.• The other examples of simplex communication modes are radio and TV transmissions.• Computer system, the keyboard, monitor and printer are examples of simplex devices.• The keyboard can only be used to enter data into computer, while monitor and printer can only accept (display/print) output.11/17/2011 MTN 2013 20
  21. 21. Half/Semi Duplex Mode• The communication can take place in both directions, but only in one direction at a time.• In this mode, data is sent and received alternatively. It is like a one-lane bridge where two-way traffic must give way in order to cross the other.• In half-duplex mode, at a time only one end transmits data while other end receives.• In addition, it is possible to perform error detection and request the sender to re-transmit information.• The Internet browsing is an example of half duplex. When we issue a request to download a web document, then that document is downloaded and displayed before we issue another request.11/17/2011 MTN 2013 21
  22. 22. Full Duplex Mode• The communication can take place in both directions simultaneously, i.e. at the same time on the same channel.• It is the fastest directional mode of communication.• Example of this mode is conversation of the persons through telephone.• This type of communication is similar to automobile traffic on a two-lane road.• The telephone communication system is an example of full duplex communication mode. 11/17/2011 MTN 2013 22
  23. 23. 5. Network Topology• The network topology defines the way in which computers, printers, and other devices are connected. A network topology describes the layout of the wire and devices as well as the paths used by data transmissions.11/17/2011 MTN 2013 23
  24. 24. Bus Topology Commonly referred to as a linear bus, all the devices on a bus topology are connected by one single cable.11/17/2011 MTN 2013 24
  25. 25. Bus Topology• Advantages • Disadvantages – It is easy to handle – The cable length is and implement. limited. This limits the number of stations – It is best suited for that can be connected. small networks. – This network topology can perform well only for a limited number of nodes.11/17/2011 MTN 2013 25
  26. 26. Star & Tree Topology The star topology is the most commonly used architecture in Ethernet LANs. When installed, the star topology resembles spokes in a bicycle wheel. Larger networks use the extended star topology also called tree topology. When used with network devices that filter frames or packets, like bridges, switches, and routers, this topology significantly reduces the traffic on the wires by sending packets only to the wires of the destination host.11/17/2011 MTN 2013 26
  27. 27. Star Topology• Advantages • Disadvantages – Due to its centralized – The network operation nature, the topology depends on the offers simplicity of functioning of the operation. central hub. – It also achieves an – Hence, the failure of the isolation of each device central hub leads to the in the network. failure of the entire network. Hub11/17/2011 MTN 2013 27
  28. 28. Tree Topology• A tree topology is a hierarchical computer network that is a combination of star and bus topologies.• Allows for multiple hubs to exist on a network which act as roots for terminals connected to them.• This tree like branched structure of networks provides high scalability.11/17/2011 MTN 2013 28
  29. 29. Tree Topology• Advantages • Disadvantages – It is the best topology for a large - Dependence of the entire network computer network for which a star on one central hub is a point of topology or ring topology are unsuitable vulnerability for this topology. A due to the sheer scale of the entire failure of the central hub or failure of network. the main data trunk cable, can – Tree topology divides the whole cripple the whole network. network into parts that are more easily manageable. Tree topology makes it - With increase in size beyond a possible to have a point to point point, the management becomes network. difficult. – All computers have access to their immediate neighbors in the network and also the central hub. This kind of network makes it possible for multiple network devices to be connected with the central hub. – It overcomes the limitation of star network topology, which has a limitation of hub connection points and the broadcast traffic induced limitation of a bus network topology. A tree network provides enough room for future expansion of a network. 11/17/2011 MTN 2013 29
  30. 30. Ring Topology A frame travels around the ring, stopping at each node. If a node wants to transmit data, it adds the data as well as the destination address to the frame. The frame then continues around the ring until it finds the destination node, which takes the data out of the frame. Single ring – All the devices on the network share a single cable Dual ring – The dual ring topology allows data to be sent in both11/17/2011 directions. MTN 2013 30
  31. 31. Ring Topology• Advantages • Disadvantages – The data being – The failure of a single transmitted between node of the network can two nodes passes cause the entire network through all the to fail. intermediate nodes. – The movement or – A central server is not changes made to required for the network nodes affects management of this the performance of the topology. entire network.11/17/2011 MTN 2013 31
  32. 32. Mesh Topology The mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance. It is used in WANs to interconnect LANs and for mission critical networks like those used by banks and financial institutions. Implementing the mesh topology is expensive and difficult.11/17/2011 MTN 2013 32
  33. 33. Mesh Topology• Advantages • Disadvantages – The arrangement – The arrangement of wherein every network the network nodes is node is connected to such that it is every other node of the network, many of possible to transmit the connections serve data from one node no major purpose. to many other nodes – This leads to the redundancy of many of at the same time. the network connections.11/17/2011 MTN 2013 33
  34. 34. END Q&A11/17/2011 MTN2013CNT 34