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Lec introduction to networking


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Lec introduction to networking

  1. 1. 1Introduction to Networking and Local-Area Networks © 2008 The McGraw-Hill Companies
  2. 2. 2 Topics Covered Network Fundamentals LAN Hardware Ethernet LANs Token-Ring LAN © 2008 The McGraw-Hill Companies
  3. 3. 3 12-1: Network Fundamentals A network is a communication system with two or more stations that can communicate with one another. When it is desired to have each computer communicate with two or more additional computers, the interconnections can become complex. The number of links L required between N PCs (nodes) is determined by using the formula L = N(N−1) / 2 The number of links or cables increases in proportion to the number of nodes involved © 2008 The McGraw-Hill Companies
  4. 4. 4 Network Fundamentals  Each computer or user in a network is referred to as a node.  The interconnection between the nodes is referred to as the communication link.A network of four PCs. © 2008 The McGraw-Hill Companies
  5. 5. 5 Network FundamentalsTypes of Networks  There are four basic types of networks:  Wide-area networks (WANs),  Metropolitan-area networks (MANs)  Local-area networks (LANs)  Personal-area networks (PANs) © 2008 The McGraw-Hill Companies
  6. 6. 6 Network FundamentalsWide-Area Networks (WANs)  A WAN covers a significant geographical area.  Local telephone systems are WANs, as are the many long-distance telephone systems linked together across the country and to WANs in other countries.  The nationwide and worldwide fiber-optic networks set up since the mid-1990s to carry Internet traffic are also WANs.  Known as the Internet core or backbone, these high- speed interconnections are configured as either direct point-to-point links or large rings with multiple access points © 2008 The McGraw-Hill Companies
  7. 7. 7 Network FundamentalsMetropolitan-Area Networks (MANs)  MANs are smaller than WANs and generally cover a city, town, or village.  Cable TV systems are MANs.  Other types of MANs, or metro networks as they are typically called, carry computer data.  MANs are usually fiber-optic rings encircling a city that provide local access to users. Businesses, governments, schools, hospitals, and others connect their internal LANs to them. © 2008 The McGraw-Hill Companies
  8. 8. 8 Network FundamentalsLocal-Area Networks (LANs)  A LAN is the smallest type of network in general use.  A LAN consists primarily of personal computers interconnected within an office or building.  LANs can have as few as three to five users, although most systems connect to several thousand users. © 2008 The McGraw-Hill Companies
  9. 9. 9 Network FundamentalsPersonal-Area Networks (PANs).  A PAN is a short-range wireless network that is set up automatically between two or more devices such as laptop computers, personal digital assistants (PDAs), peripheral devices, or cell phones.  The distance between the devices is very short, no more than about 10 m and usually much less.  PANs are referred to as ad hoc networks that are set up for a specific single purpose, such as the transfer of data between the devices as required by some application. © 2008 The McGraw-Hill Companies
  10. 10. 10 Network FundamentalsStorage-Area Networks (SANs)  SANs are an outgrowth of the massive data storage requirements developed over the years  These networks usually attach to a LAN or Internet server and store and protect huge data files.  The SAN also provides network users access to massive data files stored in mass memory units, called redundant arrays of independent disks (RAIDs).  RAIDs use many hard drives interconnected to the network and may be located anywhere since access can be via the Internet or a fiber-optic WAN or MAN. © 2008 The McGraw-Hill Companies
  11. 11. 11 Network FundamentalsNetwork Topologies  The topology of a network describes the basic communication paths between, and methods used to connect, the nodes on a network.  The three most common topologies used in LANs are star, ring, and bus. © 2008 The McGraw-Hill Companies
  12. 12. 12 Network FundamentalsStar Topology  A basic star configuration consists of a central controller node and multiple individual stations connected to it.  The central or controlling PC, often referred to as the server, is typically larger and faster than the other PCs and contains a large hard drive where shared data and programs are stored. © 2008 The McGraw-Hill Companies
  13. 13. 13 Network FundamentalsStar Topology  A star-type LAN is extremely simple and straightforward.  New nodes can be quickly and easily added to the system, and the failure of one node does not disable the entire system.  If the server node goes down, the network is disabled but individual PCs will continue to operate independently.  Star networks generally require more cable tha other network topologies © 2008 The McGraw-Hill Companies
  14. 14. 14 Network FundamentalsRing Topology  In a ring configuration, the server or main control computer and all the computers are simply linked together in a single closed loop.  Usually, data is transferred around the ring in only one direction, passing through each node. © 2008 The McGraw-Hill Companies
  15. 15. 15 The ring topology is easily implemented and low in cost. The downside of a ring network is that a failure in a single node generally causes the entire network to go down. It is also difficult to diagnose problems on a ring. © 2008 The McGraw-Hill Companies
  16. 16. 16 Network FundamentalsBus Topology  A bus is a common cable to which all of the nodes are attached.  The bus is bidirectional in that signals can be transmitted in either directions between any two nodes.  Only one node can transmit at a given time. © 2008 The McGraw-Hill Companies
  17. 17. 17 A signal to be transmitted can be destined for a single node, or transmitted or broadcast to all nodes simultaneously. The bus is faster than other topologies, wiring is simple, and the bus can be easily expanded © 2008 The McGraw-Hill Companies
  18. 18. 18 Network FundamentalsMesh Topology  A mesh network is one in which each node is connected to all other nodes.  In a full mesh, every node can talk directly to any other node.  There are major costs and complications as the number of nodes increases © 2008 The McGraw-Hill Companies
  19. 19. 19 Network FundamentalsOther Topologies.  The daisy chain topology is a ring that has been broken.  The tree topology is a bus design in which each node has multiple interconnections to other nodes through a star interconnection. © 2008 The McGraw-Hill Companies
  20. 20. 20 Network FundamentalsClient-Server and Peer-to-Peer LANs  Most LANs conform to one of two general configurations: client-server or peer-to-peer.  In the client-server type, one of the computers in the network, the server, essentially runs the LAN and determines how the system operates.  The server manages printing operations of a central printer and controls access to a very large hard drive or bank of hard drives containing databases, files, and other information that the clients—the other computers on the network—can access.  The server also provides Internet access. © 2008 The McGraw-Hill Companies
  21. 21. 21 Network Fundamentals In a peer-to-peer system, any PC can serve as either client or server; any PC can have access to any other PC’s files and connected peripherals. Peer-to-peer LANs are smaller and less expensive than the client-server variety, and provide a simple way to provide network communication. Disadvantages include:  Lower performance (lower-speed transmission capability).  Manageability and security problems (any user may access any other user’s files). © 2008 The McGraw-Hill Companies
  22. 22. 22 LAN Hardware All LANs are a combination of hardware and software. The primary hardware devices are the computers, cables, and connectors. Additional hardware includes:  Network interface cards (NICs)  Repeaters  Hubs and concentrators  Bridges  Routers  Gateways © 2008 The McGraw-Hill Companies
  23. 23. 23 LAN HardwareCables  Most LANs use some type of copper wire cable to carry data from one computer to another via baseband transmission.  The three basic cable types are: 1. Coaxial cable 2. Twisted pair 3. Fiber-optic cable © 2008 The McGraw-Hill Companies
  24. 24. 24 LAN Hardware: Coaxial cable. © 2008 The McGraw-Hill Companies
  25. 25. 25 LAN HardwareTypes of twisted-pair cable. (a) Twisted-pair unshielded (UTP) cable. (b) Multipleshielded twisted-pair (STP) cable. © 2008 The McGraw-Hill Companies
  26. 26. 26 12-2: LAN HardwareTwisted-Pair Cable  The most widely used UTP is category 5 (CAT5). It can carry baseband data at rates up to 100 Mbps at a range up to 100 m.  Twisted-pair cable specifications also include attenuation and near-end cross talk figures.  Attenuation means the amount by which the cable attenuates the signal. The longer the cable, the greater the amount of loss in the cable and the smaller the output. © 2008 The McGraw-Hill Companies
  27. 27. 27 LAN HardwareTwisted-Pair Cable  Cross talk refers to the signal transferred from one twisted pair in a cable to another by way of capacitive and inductive coupling. Near-end cross talk is the signal appearing at the input to the receiving end of the cable.  Many newer office buildings are constructed with special vertical channels or chambers, called plenums, through which cables are run between floors or across ceilings.  Cable used this way, called plenum cable, must be made of fireproof material that will not emit toxic fumes if it catches fire. © 2008 The McGraw-Hill Companies
  28. 28. 28 LAN HardwareFiber-optic cable. © 2008 The McGraw-Hill Companies
  29. 29. 29 LAN HardwareCoaxial Cable Connectors  Coaxial cables in networks use two types of connectors: 1. N connectors are widely used in RF applications 2. BNC (Bayonet Neill-Concelman )connectors are commonly used for attaching test leads to measuring instruments such as oscilloscopes. © 2008 The McGraw-Hill Companies
  30. 30. 30 LAN HardwareConnectors: Coaxial Cable Connectors  BNC T connectors are used to interconnect two cables to the network hardware.  The barrel connector provides a convenient way to connect two coaxial cables.  A terminator is a special connector containing a resistor whose value is equal to the characteristic impedance of the coaxial cable (typically 50Ω). © 2008 The McGraw-Hill Companies
  31. 31. 31 LAN HardwareCommon coaxial connectors. © 2008 The McGraw-Hill Companies
  32. 32. 32 LAN HardwareBNC connector accessories and adapters. (a) T connector. (b) Barrel connector. © 2008 The McGraw-Hill Companies
  33. 33. 33 LAN HardwareConnectors: Twisted-Pair and Fiber-Optic Connectors  Most telephones attach to an outlet by way of an RJ-11 connector or modular plug.  RJ-11 connectors are used to connect PC modems to the phone line but are not used in LAN connections.  A larger modular connector known as the RJ-45 is widely used in terminating twisted pairs.  A wide range of connectors are available to terminate fiber-optic cables. © 2008 The McGraw-Hill Companies
  34. 34. 34 LAN HardwareModular (telephone) connectors used with twisted-pair cable. (a) RJ-11. (b) RJ-45. © 2008 The McGraw-Hill Companies
  35. 35. 35 LAN HardwareRepeater  A repeater is an electronic circuit that takes a partially degraded signal, boosts its level, shapes it up, and sends it on its way.  Repeaters are small, inexpensive devices that can be inserted into a line with appropriate connectors or built into other LAN equipment.  Most repeaters are really transceivers, bidirectional circuits that can both send and receive data. © 2008 The McGraw-Hill Companies
  36. 36. 36 LAN HardwareConcept of a repeater. © 2008 The McGraw-Hill Companies
  37. 37. 37 LAN HardwareHub  A hub is a central connecting box designed to receive the cable inputs from the various PC nodes and to connect them to the server.  In most cases, hub wiring physically resembles a star because all cabling comes into a central point, or hub.  Hubs are usually active devices containing repeaters. They amplify and reshape the signal and transmit it to all connection parts. © 2008 The McGraw-Hill Companies
  38. 38. 38 LAN HardwareA hub facilitates interconnections to the server. © 2008 The McGraw-Hill Companies
  39. 39. 39 LAN HardwareBridges  A bridge is a network device that is connected as a node on a network and performs bidirectional communication between two LANs.  A bridge is generally designed to interconnect two LANs with the same protocol, for example, two Ethernet networks, although some perform protocol conversion.  Remote bridges are special bridges used to connect two LANs that are separated by a long distance. © 2008 The McGraw-Hill Companies
  40. 40. 40 LAN HardwareA bridge connects two LANs. © 2008 The McGraw-Hill Companies
  41. 41. 41 LAN HardwareSwitch  A switch is a hublike device that is used to connect individual PC nodes to the network wiring.  A switch provides a means to connect or disconnect a PC from the network wiring.  Switches have largely replaced hubs in most large LANs because they greatly expand the number of possible nodes and improve performance. © 2008 The McGraw-Hill Companies
  42. 42. 42 LAN HardwareRouter  Routers are designed to connect two networks.  The main difference between bridges and routers is that routers are intelligent devices that have decision-making and switching capabilities.  The basic function of a router is to expedite traffic flow on both networks and maintain maximum performance.  Some routers are a combination of a bridge and a router. © 2008 The McGraw-Hill Companies
  43. 43. 43 LAN HardwareGateway  A gateway is another internetwork device that acts as an interface between two LANs or between a LAN and a larger computer system.  The primary benefit of a gateway is that it can connect networks with incompatible protocols and configurations.  The gateway acts as a two-way translator that allows systems of different types to communicate.  Most gateways are computers and are sometimes referred to as gateway servers. © 2008 The McGraw-Hill Companies
  44. 44. 44 LAN HardwareA gateway commonly connects a LAN to a larger host computer. © 2008 The McGraw-Hill Companies
  45. 45. 45 LAN HardwareModem  Modems are interfaces between PCs and standard telephone systems.  Modems convert the binary signals of the computer into audio-frequency analog signals compatible with the telephone system and, at the other end, convert the analog signals back into digital signals.  The most common application is one in which remote PCs use modems to connect to an Internet service provider (ISP) which provides services such as Internet access and e-mail. © 2008 The McGraw-Hill Companies
  46. 46. 46 Ethernet LANs One of the oldest and by far the most widely used of all LANs is Ethernet. Ethernet was originally developed by Xerox from an earlier specification called Alohanet (for the Palo Alto Research Center Aloha network) and then developed further by Xerox, DEC, and Intel Ethernet was named by Robert Metcalfe, one of its developers, for the passive substance called "luminiferous (light-transmitting) ether" that was once thought to pervade the universe, carrying light throughout. Ethernet was so- named to describe the way that cabling, also a passive medium, could similarly carry data everywhere throughout the network The original versions of Ethernet used a bus topology. Today, most use a physical star configuration. Ethernet uses baseband data-transmission methods. The serial data to be transmitted is placed directly on the bus media. © 2008 The McGraw-Hill Companies
  47. 47. 47 Ethernet LANsThe Ethernet bus. © 2008 The McGraw-Hill Companies
  48. 48. 48 Ethernet LANsSpeed  The standard transmission speed for Ethernet LANs is 10 Mbps.  The most widely used version of Ethernet is called Fast Ethernet (100BASE-T). It has a speed of 100 Mbps.  Other versions of Ethernet run at speeds of 1 Gbps or 10 Gbps, typically over fiber-optic cable but also on shorter lengths of coaxial or twisted-pair cable. © 2008 The McGraw-Hill Companies
  49. 49. 49 Ethernet LANsTransmission Medium: Coaxial Cable  The original transmission medium for Ethernet was coaxial cable. However, today twisted-pair versions of Ethernet are more popular.  The two main types of coaxial cable used in Ethernet networks are RG-8/U and RG-58/U.  RG-8/U cable is known as thick cable, and large type- N coaxial connectors are used to make the interconnections. © 2008 The McGraw-Hill Companies
  50. 50. 50 Ethernet LANsTransmission Medium: Coaxial Cable  Ethernet systems using thick coaxial cable are generally referred to as 10Base-5 systems:  10 means a 10-Mbps speed  Base means baseband operation  5 designates a 500-m maximum distance between nodes, transceivers, or repeaters.  Ethernet LANs using thick cable are also referred to as Thicknet. © 2008 The McGraw-Hill Companies
  51. 51. 51 Ethernet LANsThe Ethernet (10Base-5) bus. © 2008 The McGraw-Hill Companies
  52. 52. 52 Ethernet LANsTransmission Medium: Coaxial Cable  Ethernet systems implemented with thinner coaxial cable are known as 10Base-2, or Thinnet systems.  The 2 indicates the maximum 200-m (actually, 185-m) run between nodes or repeaters.  The most widely used thin cable is RG-58/U.  It is much more flexible and easier to work with than RG-8/U cable. © 2008 The McGraw-Hill Companies
  53. 53. 53 12-3: Ethernet LANs10Base-2 coaxial Ethernet bus. © 2008 The McGraw-Hill Companies
  54. 54. 54 12-3: Ethernet LANsTransmission Medium: Twisted-Pair Cable  More recent versions of Ethernet use twisted-pair cable.  The twisted-pair version of Ethernet is referred to as a 10Base-T network, where the T stands for twisted-pair. © 2008 The McGraw-Hill Companies
  55. 55. 55 12-3: Ethernet LANsTransmission Medium: Gigabit Ethernet  Gigabit Ethernet (1 GE) is capable of achieving 1000 Mbps or 1 Gbps over category 5 UTP or fiber-optic cable. © 2008 The McGraw-Hill Companies
  56. 56. 56 Token-Ring LAN In the Token-Ring configuration, all of the nodes or PCs in the network are connected end to end in a continuous circle or loop. Data in the network travels in only one direction on the ring. The transmitted information passes through the NICs of each PC in the loop. Token Ring uses baseband transmission; the binary data is placed directly on the cable. Token-ring LANs use twisted pair cable and connections are made by using RJ-45 modular connectors. © 2008 The McGraw-Hill Companies
  57. 57. 57 Token-Ring LANToken-Ring wiring. © 2008 The McGraw-Hill Companies