Network Topologies 5/11/10

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Network Topologies 5/11/10

  1. 1. Network Topologies
  2. 2. Objectives <ul><li>Describe the basic and hybrid LAN physical topologies, their uses, advantages, and disadvantages </li></ul><ul><li>Describe a variety of enterprise-wide and WAN physical topologies, their uses, advantages, and disadvantages </li></ul><ul><li>Compare the different types of switching used in data transmission </li></ul><ul><li>Understand the transmission methods, or logical topologies, underlying Ethernet, Token Ring, LocalTalk, and FDDI networks </li></ul>
  3. 3. Simple Physical Topologies <ul><li>Physical topology </li></ul><ul><ul><li>Physical layout of a network </li></ul></ul><ul><li>A Bus topology consists of a single cable—called a bus — connecting all nodes on a network without intervening connectivity devices </li></ul>
  4. 4. Advantages of Bus Topology <ul><li>Works well for small networks </li></ul><ul><li>Relatively inexpensive to implement </li></ul><ul><li>Easy to add to it </li></ul>
  5. 5. Disadvantages of Bus Topology <ul><li>Management costs can be high </li></ul><ul><li>Potential for congestion with network traffic </li></ul>
  6. 6. Simple Physical Topologies <ul><li>Ring topology </li></ul><ul><ul><li>Each node is connected to the two nearest nodes so the entire network forms a circle </li></ul></ul><ul><ul><li>One method for passing data on ring networks is token passing </li></ul></ul><ul><li>Active topology </li></ul><ul><ul><li>Each workstation transmits data </li></ul></ul>
  7. 7. Advantages of Ring Topology <ul><li>Easier to manage; easier to locate a defective node or cable problem </li></ul><ul><li>Well-suited for transmitting signals over long distances on a LAN </li></ul><ul><li>Handles high-volume network traffic </li></ul><ul><li>Enables reliable communication </li></ul>
  8. 8. Disadvantages of Ring Topology <ul><li>Expensive </li></ul><ul><li>Requires more cable and network equipment at the start </li></ul><ul><li>Not used as widely as bus topology </li></ul><ul><ul><li>Fewer equipment options </li></ul></ul><ul><ul><li>Fewer options for expansion to high-speed communication </li></ul></ul>
  9. 9. Simple Physical Topologies <ul><li>Star topology </li></ul><ul><ul><li>Every node on the network is connected through a central device </li></ul></ul>
  10. 10. Advantages of Star Topology <ul><li>Good option for modern networks </li></ul><ul><li>Low startup costs </li></ul><ul><li>Easy to manage </li></ul><ul><li>Offers opportunities for expansion </li></ul><ul><li>Most popular topology in use; wide variety of equipment available </li></ul>
  11. 11. Disadvantages of Star Topology <ul><li>Hub is a single point of failure </li></ul><ul><li>Requires more cable than the bus </li></ul>
  12. 12. Hybrid Physical Topologies <ul><li>Hybrid topology </li></ul><ul><ul><li>Complex combination of the simple physical topologies </li></ul></ul><ul><li>Star-wired ring </li></ul><ul><ul><li>Star-wired topologies use physical layout of a star in conjunction with token ring-passing data transmission method </li></ul></ul>
  13. 13. Hybrid Physical Topologies <ul><li>Star-wired bus </li></ul><ul><ul><li>In a star-wired bus topology , groups of workstations are star-connected to hubs and then networked via a single bus </li></ul></ul>
  14. 14. Hybrid Physical Topologies <ul><li>Daisy-Chained </li></ul><ul><ul><li>A Daisy chain is linked series of devices </li></ul></ul>
  15. 15. Hybrid Physical Topologies <ul><li>Hierarchical hybrid topology </li></ul><ul><ul><li>Uses layers to separate devices by priority or function </li></ul></ul>
  16. 16. Enterprise-Wide Topologies <ul><li>Enterprise </li></ul><ul><ul><li>An entire organization </li></ul></ul><ul><li>Backbone networks </li></ul><ul><ul><li>Serial backbone </li></ul></ul><ul><ul><li>Distributed backbone </li></ul></ul><ul><ul><li>Collapsed backbone </li></ul></ul><ul><ul><li>Parallel backbone </li></ul></ul>
  17. 17. Enterprise-Wide Topologies <ul><li>Serial backbone </li></ul><ul><ul><li>Two or more hubs connected to each other by a single cable </li></ul></ul><ul><li>Distributed backbone </li></ul><ul><ul><li>Hubs connected to a series of central hubs or routers in a hierarchy </li></ul></ul>
  18. 18. Enterprise-Wide Topologies <ul><li>Collapsed backbone </li></ul><ul><ul><li>Uses a router or switch as the single central connection point for multiple subnetworks </li></ul></ul>
  19. 19. Enterprise-Wide Topologies <ul><li>Parallel Backbone </li></ul><ul><ul><li>Collapsed backbone arrangement that consists of more than one connection from central router or switch to each network segment </li></ul></ul>
  20. 20. Enterprise-Wide Topologies <ul><li>Mesh networks </li></ul><ul><ul><li>Routers are interconnected with other routers, with at least two pathways connecting each router </li></ul></ul>
  21. 21. Wide Area Network (WAN) Topologies <ul><li>Peer-to-peer topology </li></ul><ul><ul><li>WAN with single interconnection points for each location </li></ul></ul><ul><ul><li>Dedicated circuits </li></ul></ul><ul><ul><ul><li>Continuous physical or logical connections between two access points that are leased from a communication provider </li></ul></ul></ul>
  22. 22. Wide Area Network (WAN) Topologies <ul><li>Ring WAN topology </li></ul><ul><ul><li>Each site is connected to two other sites so that entire WAN forms a ring pattern </li></ul></ul>
  23. 23. Wide Area Network (WAN) Topologies <ul><li>Star WAN topology </li></ul><ul><ul><li>Single site acts as the central connection point for several other points </li></ul></ul>
  24. 24. Wide Area Network (WAN) Topologies <ul><li>Mesh WAN topology </li></ul><ul><ul><li>Many directly interconnected locations forming a complex mesh </li></ul></ul>
  25. 25. Logical Topologies <ul><li>Refers to the way in which data are transmitted between nodes </li></ul><ul><li>Describes the way: </li></ul><ul><ul><li>Data are packaged in frames </li></ul></ul><ul><ul><li>Electrical pulses are sent over network’s physical media </li></ul></ul><ul><li>Logical topology may also be called network transport system </li></ul>
  26. 26. Switching <ul><li>Component of network’s logical topology that determines how connections are created between nodes </li></ul><ul><ul><li>Circuit switching </li></ul></ul><ul><ul><ul><li>Connection is established between two network nodes before they begin transmitting data </li></ul></ul></ul><ul><ul><li>Message switching </li></ul></ul><ul><ul><ul><li>Establishes connection between two devices, transfers information to second device, and then breaks connection </li></ul></ul></ul><ul><ul><li>Packet switching </li></ul></ul><ul><ul><ul><li>Breaks data into packets before they are transmitted </li></ul></ul></ul>
  27. 27. Ethernet <ul><li>Carrier Sense Multiple Access with Collision Detection (CSMA/CD) </li></ul><ul><ul><li>The access method used in Ethernet </li></ul></ul><ul><ul><li>Collision </li></ul></ul><ul><ul><ul><li>In Ethernet networks, the interference of one network node’s data transmission with another network node’s data transmission </li></ul></ul></ul><ul><ul><li>Jamming </li></ul></ul><ul><ul><ul><li>Part of CSMA/CD in which, upon detection of collision, station issues special 32-bit sequence to indicate to all nodes on Ethernet segment that its previously transmitted frame has suffered a collision and should be considered faulty </li></ul></ul></ul>
  28. 28. Ethernet CSMA/CD process
  29. 29. Ethernet <ul><li>On an Ethernet network, an individual network segment is known as a collision domain </li></ul><ul><ul><li>Portion of network in which collisions will occur if two nodes transmit data at same time </li></ul></ul><ul><li>Data propagation delay </li></ul><ul><ul><li>Length of time data take to travel from one point on the segment to another point </li></ul></ul>
  30. 30. Ethernet <ul><li>Demand priority </li></ul><ul><ul><li>Method for data transmission used by 100BaseVG Ethernet networks </li></ul></ul><ul><ul><li>Demand priority requires an intelligent hub </li></ul></ul>CSMA/CD versus demand priority
  31. 31. Ethernet <ul><li>Traditional Ethernet LANs, called shared Ethernet , supply fixed amount of bandwidth that must be shared by all devices on a segment </li></ul><ul><li>Switch </li></ul><ul><ul><li>Device that can separate network segments into smaller segments, with each segment being independent of the others and supporting its own traffic </li></ul></ul><ul><li>Switched Ethernet </li></ul><ul><ul><li>Newer Ethernet model that enables multiple nodes to simultaneously transmit and receive data over logical network segments </li></ul></ul>
  32. 32. Ethernet A switched Ethernet network
  33. 33. Ethernet <ul><li>Gigabit Ethernet </li></ul><ul><ul><li>1 Gigabit Ethernet </li></ul></ul><ul><ul><ul><li>Ethernet standard for networks that achieve 1-Gbps maximum throughput </li></ul></ul></ul><ul><ul><li>10 Gigabit Ethernet </li></ul></ul><ul><ul><ul><li>Standard currently being defined by IEEE 802.3ae committee </li></ul></ul></ul><ul><ul><ul><li>Will allow 10-Gbps throughput </li></ul></ul></ul><ul><ul><ul><li>Will include full-duplexing and multimode fiber requirements </li></ul></ul></ul>
  34. 34. Design Considerations for Ethernet Networks <ul><li>Cabling </li></ul><ul><li>Connectivity devices </li></ul><ul><li>Number of stations </li></ul><ul><li>Speed </li></ul><ul><li>Scalability </li></ul><ul><li>Topology </li></ul>
  35. 35. LocalTalk <ul><li>Logical topology designed by Apple Computer, Inc. </li></ul><ul><li>Uses a transmission method called Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) </li></ul><ul><li>A teleconnector is a transceiver used on a LocalTalk network </li></ul><ul><li>Macintosh version of TCP/IP is called MacTCP </li></ul>
  36. 36. Token Ring <ul><li>Token Ring networks use the token passing routine and a star-ring hybrid physical topology </li></ul><ul><li>The 100-Mbps Token Ring standard is known as High-Speed Token Ring (HSTR) </li></ul><ul><li>On a Token Ring network, one workstation, called the active monitor , acts as the controller for token passing </li></ul>
  37. 37. Token Ring <ul><li>Multistation Access Unit (MAU) </li></ul><ul><ul><li>Regenerates signals </li></ul></ul>Interconnected Token Ring MAUs
  38. 38. Token Ring <ul><li>Control Access Unit (CAU) </li></ul><ul><ul><li>Connectivity device used on a Token Ring network </li></ul></ul><ul><li>Lobe Attachment Module (LAM) </li></ul><ul><ul><li>Device that attaches to a CAU to expand the capacity of that device </li></ul></ul>
  39. 39. Token Ring <ul><li>Token Ring networks with STP cabling may use a type 1 IBM connector </li></ul><ul><li>A DB-9 connector is another type of connector found on STP Token Ring networks </li></ul>Type 1 IBM and DB-9 Token Ring connectors
  40. 40. Token Ring <ul><li>Media filter </li></ul><ul><ul><li>Device that enables two types of cables or connectors to be linked </li></ul></ul><ul><li>Token Ring media filter </li></ul><ul><ul><li>Enables DB-9 cable and type 1 IBM cable to be connected </li></ul></ul>A Token Ring media filter
  41. 41. Design Considerations for Token Ring Networks <ul><li>Cabling </li></ul><ul><li>Connectivity devices </li></ul><ul><li>Number of stations </li></ul><ul><li>Speed </li></ul><ul><li>Scalability </li></ul><ul><li>Topology </li></ul>
  42. 42. Fiber Distributed Data Interface (FDDI) <ul><li>Logical topology whose standard was originally specified by ANSI in mid-1980s and later refined by ISO </li></ul>
  43. 43. Asynchronous Transfer Mode (ATM) <ul><li>Logical topology that relies on a fixed packet size to achieve data transfer rates up to 9953 Mbps </li></ul><ul><li>The fixed packet in ATM is called a cell </li></ul><ul><li>A unique aspect of ATM technology is that it relies on virtual circuits </li></ul>
  44. 44. Asynchronous Transfer Mode (ATM) <ul><li>ATM uses circuit switching, which allows ATM to guarantee a specific quality of service (QOS) </li></ul><ul><li>ATM technology can be integrated with Ethernet or Token Ring networks through the use of LAN Emulation (LANE) </li></ul>

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