Chapter3

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Chapter3

  1. 1. LAN Technologies CMC Limited
  2. 2. Objectives • Understand different types of LAN technologies. • Understand LAN transmission methods. • Understand LAN topology. • Explain different LAN media access methods. • Understand several types of cabling used with LAN. • Understand different types of protocols. • Understand Ethernet technology. • Understand different types of Ethernet collisions. • Explain different causes of physical frame corruption. • Understand LAN segmentation. CMC Limited
  3. 3. LAN Technology A local area network (LAN) is a group of computers and associated devices that share a common communications line or wireless link and typically share the resources of a single processor or server within a small geographic area. The most common local area networking technologies are: • Ethernet • LocalTalk • Token Ring • FDDI CMC Limited
  4. 4. LAN Technology contd..Ethernet The Ethernet protocol is by far the most widely used. Ethernet uses an access method called CSMA/CD (Carrier Sense Multiple Access/Collision Detection). The Ethernet protocol allows for linear bus, star, or tree topologies. Data can be transmitted over twisted pair, coaxial, or fiber optic cable at a speed of 10 Mbps. CMC Limited
  5. 5. LAN Technology contd..LocalTalk LocalTalk is a network protocol that was developed by Apple Computer Inc. for Macintosh computers. The method used by LocalTalk is called CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance). LocalTalk adapters and special twisted pair cables can be used to connect a series of computers through the serial port. The LocalTalk protocol allows for linear bus, star, or tree topologies using twisted pair cable. A primary disadvantage of LocalTalk is speed. Its speed of transmission is only 230 Kbps. CMC Limited
  6. 6. LAN Technology contd..Token Ring The Token Ring technology was developed by IBM in the mid 1980s. The access method used involves token-passing. In Token Ring, the computers are so connected that the signal travels around the network from one computer to another in a logical ring. Token Ring protocol requires a star-wired ring using twisted pair or fiber optic cable. It can operate at transmission speeds of 4 Mbps or 16 Mbps. CMC Limited
  7. 7. Token Ring contd..CMC Limited
  8. 8. LAN Technology contd..FDDI Fiber Distributed Data Interface (FDDI) is a network protocol that is used primarily to interconnect two or more local area networks, often over large distances. The access method used by FDDI involves token-passing. FDDI uses a dual ring physical topology. A major advantage of FDDI is speed. It operates over fiber optic cable at 100 Mbps. CMC Limited
  9. 9. LAN Technology contd..Summary of General LAN Technologies LAN Cable Speed Topology Technology Twisted Pair, Coaxial, Linear Bus, Star,Ethernet 10 Mbps Fiber TreeFast Ethernet Twisted Pair, Fiber 100 Mbps StarLocalTalk Twisted Pair .23 Mbps Linear Bus or Star 4 Mbps - 16Token Ring Twisted Pair Star-Wired Ring MbpsFDDI Fiber 100 Mbps Dual ring CMC Limited
  10. 10. LAN Types To understand a LAN we need to explore the manner in which network attached resources are shared in a LAN. The two prevailing types are: • Peer-to-Peer • Client/Server CMC Limited
  11. 11. LAN Types contd..Peer-to-Peer Peer-to-peer access control allows users to share resources and files located on their computers and to access shared resources found on other computers. In a peer-to-peer network, all computers are considered equal. Peer-to-peer networks are designed primarily for small to medium local area networks. CMC Limited
  12. 12. Peer-to-Peer contd..Some operating systems, like AppleShare, Windows forWorkgroups and Windows 95/98 are specially featured forpeer-to-peer network access. CMC Limited
  13. 13. LAN Types contd..Client/Server Client/server network operating systems allow the network to centralize functions and applications in one or more dedicated file servers. Novell Netware and Windows NT Server are examples of client/server network operating systems. CMC Limited
  14. 14. LAN Types contd..Advantages• Centralized• Scalability• Flexibility• Interoperability• AccessibilityDisadvantages• Expense• Maintenance• Dependence CMC Limited
  15. 15. LAN Transmission Methods LAN data transmissions fall into three classifications: • Unicast: A single packet is sent from the source to a destination on a network • Multicast: A single data packet that is copied and sent to a specific subset of nodes on the network. • Broadcast: A single data packet that is copied and sent to all nodes on the network. CMC Limited
  16. 16. Topology The physical topology of a network refers to the configuration of cables, computers and other peripherals. There are four principal topologies used in LANs. • Bus Topology • Ring Topology • Star Topology • Tree Topology CMC Limited
  17. 17. Topology contd..Bus Topology Bus topology consists of a main run of cable with a terminator at each end. All nodes such as, file server, workstations and other peripherals, are connected to the main cable. CMC Limited
  18. 18. Topology contd..Ring Topology Ring topology consists of nodes arranged in a ring pattern. CMC Limited
  19. 19. Topology contd..Star Topology Star topology is designed with each node (file server, workstations and peripherals) connected directly to a central Network HUB. CMC Limited
  20. 20. Topology contd..Tree Topology Tree topology combines BUS and STAR topologies. It consists of a group of star-configured workstations connected to a Bus backbone cable. CMC Limited
  21. 21. LAN Media-Access Methods Media contention occurs when two or more network devices have data to send at the same time. Multiple devices cannot talk on the network simultaneously, some type of method must be used to allow one device access to the network media at a time. This is done in two main ways: • Carrier Sense Multiple Access Collision Detect (CSMA/CD) • Token Passing CMC Limited
  22. 22. Cabling Cable is the medium through which information usually moves from one network device to another. The type of cable chosen for a network is related to the networks topology, protocol, and size. There are several types of cable which are commonly used with LANs. Some of them are as follows: • Twisted-Pair Cable • Coaxial Cable • Fiber Optic Cable CMC Limited
  23. 23. Cabling contd..Twisted-Pair Cable Twisted pair cabling comes in two varieties: • Shielded Twisted-Pair Cable • Unshielded Twisted-Pair Cable Shielded Twisted-Pair (STP) Cable Shielded twisted pair (STP) is suitable for environments with electrical interference; however, the extra shielding can make the cables quite bulky. Shielded twisted pair is often used on networks using Token Ring topology. CMC Limited
  24. 24. Twisted-Pair Cable contd..Unshielded Twisted-Pair CableUTP cable has four pairs of wires inside the jacket. Eachpair is twisted with a different number of twists per inch tohelp eliminate interference from adjacent pairs and otherelectrical devices. CMC Limited
  25. 25. Cabling contd..Coaxial Cable Coaxial cables consist of one or more cables in a protective cover. It has a single copper conductor at its center. A plastic layer provides insulation between the center conductor and an outer metal shield. CMC Limited
  26. 26. Coaxial Cable contd..The two types of coaxial cabling are:• Thick coaxial• Thin coaxialCoaxial Cable ConnectorsThe most common type of connector used with coaxialcables is the Bayone-Neill-Concelman (BNC) connector. CMC Limited
  27. 27. Cabling contd..Fiber Optic Cable Fiber optic cabling consists of a center glass core surrounded by several layers of protective materials. Outer insulating jacket is made of Teflon or PVC. Center (core) is made of Glass or plastic fibers. A plastic coating is used to cushion the fiber center. CMC Limited
  28. 28. Cabling contd..Ethernet Cable Summary Specification Cable type Maximum length10BaseT Unshielded Twisted Pair 100 meters10Base2 Thin Coaxial 185 meters10Base5 Thick Coaxial 500 meters10BaseF Fiber Optic 2000 meters100BaseT Unshielded Twisted Pair 100 meters100BaseTX Unshielded Twisted Pair 220 meters CMC Limited
  29. 29. Protocols Internet Protocol (IP): A network protocol that specifies the format of packets, also called datagrams, and the addressing scheme. Terminal Control Protocol (TCP): A primary protocol in TCP/IP networks. TCP allows two "hosts" in a TCP/IP network to establish a connection and exchange streams of data. CMC Limited
  30. 30. Ethernet Technology Ethernet is the most widely installed local area network (LAN) technology. • Traditional Ethernet supports data transfers at the rate of 10 Megabits per second (Mbps). • Fast Ethernet extends traditional Ethernet performance up to 100 Mbps. • Gigabit Ethernet boasts the same order-of-magnitude improvement over Fast Ethernet by offering speeds of 1000 Megabits (1 Gigabit). CMC Limited
  31. 31. Ethernet Technology contd..Details of Traditional Ethernet Technologies Segment Length Name Cable (Max.)10Base5 500m / 1640ft. RG-8 or RG-11 coaxial10Base2 185m / 606ft. RG 58 A/U or RG 58 C/U coaxial Category 3 or better unshielded10Base-T 100m / 328ft. twisted pair CMC Limited
  32. 32. Ethernet Technology contd..Fast Ethernet Fast Ethernet technology matured and met its design goals of: • increasing the performance of traditional Ethernet • avoiding the need to completely re-cable existing Ethernet networks Fast Ethernet comes in two major varieties: • 100Base-T (using unshielded twisted pair cable) • 100Base-FX (using fiber optic cable) CMC Limited
  33. 33. Ethernet Technology contd..Gigabit Ethernet Gigabit Ethernet was first made to travel over optical and copper cabling, but the 1000Base-T standard successfully supports it as well. 1000Base-T uses Category 5 cabling similar to 100 Mbps Ethernet, although achieving gigabit speed requires the use of additional wire pairs. CMC Limited
  34. 34. Half-Duplex Half-Duplex data transmission means that data can be transmitted in both directions on a signal carrier, but not at the same time. Example: Walkie-talkie; push button to talk, one speaker at a time. CMC Limited
  35. 35. Full Duplex Full-duplex data transmission means that data can be transmitted in both directions on a signal carrier at the same time. When switches are introduced, full-duplex operation is possible. Example: Telephone; both parties can speak and hear at the same time. CMC Limited
  36. 36. Ethernet Collisions A collision is an event that happens on an Ethernet network when two stations simultaneously "talk" on the wire. There are two different type of collisions namely: • Early Ethernet Collisions • Late Ethernet Collisions CMC Limited
  37. 37. Ethernet Collisions contd..Early Collisions An early collision is any collision that occurs before 512 bits of the frame have been put onto the wire. CMC Limited
  38. 38. Ethernet Collisions contd..Late Collisions A late collision is defined as any collision that occurs after 512 bits of the frame have been transmitted. CMC Limited
  39. 39. Physical Frame Corruption When troubleshooting your Ethernet network, the first thing to look for is physical frame corruption. The following are the four possible causes of physical frame corruption in an Ethernet Network. • Collisions: Caused by faulty hardware. • Signal Reflections: Caused by un-terminated cables, impedance mismatch and exceeding the maximum allowable bend radius of the cable. • Electrical Noise: Caused by nearby power grids, fluorescent lighting, X-ray machines etc. • Malfunctioning Hardware: Caused by gremlins, helpful users, natural disasters etc. CMC Limited
  40. 40. LAN Segmentation When separate networks are needed or if a network has reached its physical limitations, segmentation is used. Segmenting a LAN can extend the network, reduce congestion, isolate network problems, and improve security. The advantages of LAN segmentation are as follows: • Extending the Network • Reduce Congestion • Isolate Network Problems • Improve Security CMC Limited
  41. 41. LAN Segmentation contd..LAN Segmentation Using Bridges The term bridging refers to a technology in which a device (known as a bridge) connects two or more LAN segments. A bridge transmits datagrams from one segment to their destinations on other segments. CMC Limited
  42. 42. LAN Segmentation contd..LAN Segmentation Using Routers Segments are interconnected by routers to enable communication between LANs while blocking other types of traffic.LAN Segmentation Using Switches Switches are data link layer devices that, like bridges, enable multiple physical LAN segments to be interconnected into a single larger network. LAN switches can be used to segment networks into logically defined virtual workgroups (VLANs). CMC Limited
  43. 43. LAN Segmentation contd..Benefits of Network Segmentation withBridges Transparent bridges successfully isolate intrasegment traffic, thereby reducing the traffic seen on each individual segment. This usually improves network response times, as seen by the user.Benefits of Network Segmentation withRouters • Media Transition • Broadcast Control • Packet Filtering • VLAN Communications • Large Packets CMC Limited
  44. 44. LAN Segmentation contd..Benefits of Network Segmentation withSwitches The benefits of network segmentation with switches are as follows: • Allow multiple data streams to pass simultaneously. • Provides dedicated, collision-free communication between network devices, with support for multiple simultaneous conversations. • Reduce collisions on network segments. • Provide excellent performance for individual users by allocating dedicated bandwidth to each switch port. • Deliver dedicated bandwidth to users. • Group individual ports into logical switched workgroups called VLANs. CMC Limited

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