Data Communications - Chapter ten


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Data Communications - Chapter ten

  1. 1. High-Speed LAN and Backbone Networks <ul><li>After studying this Chapter you should: </li></ul><ul><ul><li>Know which internetworking devices are used in backbone networks </li></ul></ul><ul><ul><li>Describe several types of fast Ethernet and fast Token Ring </li></ul></ul><ul><ul><li>Describe FDDI </li></ul></ul><ul><ul><li>Describe ATM and fiber channels </li></ul></ul><ul><ul><li>Know ways to improve performance on BN </li></ul></ul>
  2. 2. Definition <ul><li>Backbone Network (BN) - a large high-speed central network that connects all the terminals, microcomputers, mainframes, local area networks, and other communications equipment on a single company or site. Sometimes called a Campus Area Network (CAN). Use Higher speed circuits for connectivity. </li></ul>
  3. 3. Definition <ul><li>Enterprise Network (EN) - a supernetwork that interconnects all of an organizations networks (LANs and WANs), regardless of whether it crosses state, national, or international boundaries. </li></ul>
  4. 4. Why interconnect networks? <ul><li>Reliability </li></ul><ul><li>Performance </li></ul><ul><li>Security </li></ul>
  5. 5. Introduction <ul><li>There are two approaches to providing high speed networking. </li></ul><ul><ul><li>“speed up” the technologies currently used in local area networks. </li></ul></ul><ul><ul><ul><li>Fast Ethernet </li></ul></ul></ul><ul><ul><ul><li>Fast Token Ring </li></ul></ul></ul><ul><ul><li>develop new high speed technologies that provide dedicated point-to-point communication circuits </li></ul></ul><ul><ul><ul><li>Switched Ethernet </li></ul></ul></ul><ul><ul><ul><li>Switched Token Ring </li></ul></ul></ul><ul><ul><ul><li>ATM </li></ul></ul></ul>
  6. 6. Backbone Network Components <ul><li>Two basic components to the BN </li></ul><ul><ul><li>hardware devices that connect the networks to the backbone </li></ul></ul><ul><ul><ul><li>hubs </li></ul></ul></ul><ul><ul><ul><li>bridges </li></ul></ul></ul><ul><ul><ul><li>switches </li></ul></ul></ul><ul><ul><ul><li>routers </li></ul></ul></ul><ul><ul><ul><li>brouters </li></ul></ul></ul><ul><ul><ul><li>gateways </li></ul></ul></ul><ul><ul><li>network cable </li></ul></ul>
  7. 7. Hubs <ul><ul><li>very simple devices that pass all traffic in both directions between the LAN sections they link </li></ul></ul><ul><ul><li>same or different cable types </li></ul></ul><ul><ul><li>use physical layer protocols </li></ul></ul><ul><ul><li>pass on every message </li></ul></ul><ul><ul><li>used to connect LANs of similar technology, or to extend the distance of one LAN </li></ul></ul><ul><ul><li>can be called repeaters or amplifiers </li></ul></ul>
  8. 8. HUB Devices HUB (MAU) Repeater/Amplifier
  9. 9. Hubs <ul><ul><li>inexpensive </li></ul></ul><ul><ul><li>easy to Install </li></ul></ul><ul><ul><li>can connect different media </li></ul></ul><ul><ul><li>very little delay </li></ul></ul><ul><ul><li>limited distance between devices </li></ul></ul><ul><ul><li>limited on the number of repeaters </li></ul></ul><ul><ul><li>no protocol or rate conversion </li></ul></ul><ul><ul><li>no error detection </li></ul></ul><ul><ul><li>does not filter </li></ul></ul>
  10. 10. Bridges <ul><ul><li>connect two LAN segments that use the same data link and network protocol </li></ul></ul><ul><ul><li>operated at the data link layer </li></ul></ul><ul><ul><li>same or different cable types </li></ul></ul><ul><ul><li>forward only those messages that need to go out (filtering) </li></ul></ul><ul><ul><li>“learn” whether to forward packets </li></ul></ul><ul><ul><li>internal routing table </li></ul></ul><ul><ul><li>combination of “black box” hardware and software </li></ul></ul>
  11. 11. Bridges <ul><li>There are three types of bridges: </li></ul><ul><li>Simple bridge </li></ul><ul><li>Learning bridge </li></ul><ul><li>Multiport bridge </li></ul>
  12. 12. Bridges Interconnecting Bridge HUB (MAU) Repeater/ Amplifier HUB (MAU) Repeater/ Amplifier
  13. 13. Bridges <ul><ul><li>may be different data rates and different media easy to Install </li></ul></ul><ul><ul><li>no modifications required to the communications software </li></ul></ul><ul><ul><li>can learn the ports for data transmission </li></ul></ul><ul><ul><li>understand only data link layer protocols and addresses </li></ul></ul><ul><ul><li>no protocol conversion </li></ul></ul><ul><ul><li>broadcasts when it does not know the address </li></ul></ul>
  14. 14. Switches <ul><ul><li>connect more than two LAN segments that use the same data link and network protocol. </li></ul></ul><ul><ul><li>operate at the data link layer </li></ul></ul><ul><ul><li>same or different type cable </li></ul></ul><ul><ul><li>ports are usually provided for 4, 8, 16, or 32 LAN segments </li></ul></ul><ul><ul><li>ports are used simultaneously </li></ul></ul><ul><ul><li>connect lower speed segments to high speed BN </li></ul></ul>
  15. 15. Switches <ul><li>Cut-through switches </li></ul><ul><ul><li>use circuit-switching to immediately connect the port with the incoming message to the correct outgoing port </li></ul></ul><ul><ul><li>very fast as decisions are done in hardware </li></ul></ul><ul><ul><li>outgoing packet is lost if port is in use </li></ul></ul><ul><li>Store-and-forward switches </li></ul><ul><ul><li>copy the incoming packet to memory prior to processing the destination address -- transmit it when the outgoing port is ready </li></ul></ul>
  16. 16. Switches Interconnecting Wing C Wing C Wing A Wing B First Floor Switch
  17. 17. Switches <ul><ul><li>much more sophisticated than previously </li></ul></ul><ul><ul><li>enable all ports to work at the same time </li></ul></ul><ul><ul><li>can convert protocols </li></ul></ul><ul><ul><li>configurable </li></ul></ul><ul><ul><li>high speed </li></ul></ul><ul><ul><li>understand only data link layer protocols and addresses </li></ul></ul><ul><ul><li>much more expensive then previous options </li></ul></ul><ul><ul><li>higher maintenance </li></ul></ul>
  18. 18. Routers <ul><ul><li>connect two or more LANs that use the same or different data link protocols, but the same network protocol. </li></ul></ul><ul><ul><li>same or different cable types </li></ul></ul><ul><ul><li>operate at the network layer </li></ul></ul><ul><ul><li>forward only messages that need to go out </li></ul></ul><ul><ul><li>routers use the internetwork address </li></ul></ul><ul><ul><li>internal routing tables </li></ul></ul><ul><ul><li>only processes messages addressed to it </li></ul></ul>
  19. 19. Routers <ul><li>choose the best route to send the packet (path) </li></ul><ul><ul><li>IDs of other networks </li></ul></ul><ul><ul><li>paths to the networks </li></ul></ul><ul><ul><li>relative efficiency of the paths </li></ul></ul>
  20. 20. Routers <ul><li>The router must deal with network differences: </li></ul><ul><ul><li>addressing schemes </li></ul></ul><ul><ul><li>minimum packet size </li></ul></ul><ul><ul><li>interfaces </li></ul></ul><ul><ul><li>reliability </li></ul></ul>
  21. 21. Routers Interconnecting Router Ethernet LAN2 Token Ring LAN1 X.25 Network the “cloud”
  22. 22. Routers <ul><ul><li>can mix-in-match protocols and convert them </li></ul></ul><ul><ul><li>enable all ports to work at the same time </li></ul></ul><ul><ul><li>can be used as an extra layer of security </li></ul></ul><ul><ul><li>configurable </li></ul></ul><ul><ul><li>high speed </li></ul></ul><ul><ul><li>hard to configure and manage </li></ul></ul><ul><ul><li>access lists must be kept current </li></ul></ul><ul><ul><li>high maintenance/high training costs </li></ul></ul><ul><ul><li>very expensive </li></ul></ul>
  23. 23. Brouters <ul><ul><li>devices that combine the functions of both bridges and routers </li></ul></ul><ul><ul><li>operate at both the data link and network layers </li></ul></ul><ul><ul><li>same or different data link protocol </li></ul></ul><ul><ul><li>same network protocol </li></ul></ul><ul><ul><li>as fast as bridges for same data link type networks </li></ul></ul>
  24. 24. Gateways <ul><ul><li>complex machines that are interfaces between two or more dissimilar networks </li></ul></ul><ul><ul><li>connect two or more LANs that use the same or different data link layer, network layer, and cable types </li></ul></ul><ul><ul><li>operates at the network layer (3) or higher layers (4-7) </li></ul></ul><ul><ul><li>forwards only those messages that need to go out </li></ul></ul><ul><ul><li>a combination of both hardware and software </li></ul></ul>
  25. 25. Gateways <ul><ul><li>translates one network protocol to another </li></ul></ul><ul><ul><li>translates data formats </li></ul></ul><ul><ul><li>translates open sessions between application programs </li></ul></ul><ul><ul><li>translates to mainframes </li></ul></ul>
  26. 26. Gateways <ul><li>Exists in four major types: </li></ul><ul><ul><li>LAN-to-IBM mainframe </li></ul></ul><ul><ul><li>Network-to-network </li></ul></ul><ul><ul><li>System-to-network </li></ul></ul><ul><ul><li>System-to-system </li></ul></ul>
  27. 27. LAN-to-IBM Mainframe <ul><li>Allow LANs using TCP/IP and Ethernet to be connected to IBM mainframe using SNA </li></ul><ul><li>Eliminates the need for each PC on the LAN to have SNA hardware/software that makes it act like an IBM 3270 terminal </li></ul>Gateway Mainframe
  28. 28. Network-to-Network X.75 Gateway X.25 Network A X.25 Network B X.75 provides terminal address translation
  29. 29. System-to-Network X.25 Network Gateway Minicomputer or Microcomputer
  30. 30. System-to-System <ul><ul><li>allows connecting one vendor’s architecture to another vendor’s architecture </li></ul></ul><ul><ul><li>allows both the existence of OSI-based and proprietary architectures (like SNA or AppleTalk) </li></ul></ul><ul><ul><li>gives management to tools necessary to plan a gradual migration to a completely OSI environment </li></ul></ul><ul><ul><li>applications can work with other application </li></ul></ul>
  31. 31. System-to-System X.25 Network LAN E-mail Gateway LAN E-mail Server Profs E-mail Profs E-mail Gateway
  32. 32. Backbone Network Devices Hub Physical All transferred S/D Same Same Bridge Data link Filtered using S/D Same Same data link layer add. Switch Data link Switched using S/D Same Same data link layer add. Router Network Routed using S/D S/D Same network layer add. Brouter Data link & Filtered & routed S/D S/D Same Network Gateway Network Routed using S/D S/D S/D network layer add. Physical Data Link Network Device Operates at Messages Layer Layer Layer
  33. 33. Terminology Warnings <ul><ul><li>Multiprotocol bridges translate between different data link layer protocols. </li></ul></ul><ul><ul><li>Multiprotocol routers translate between different network layer protocols. </li></ul></ul><ul><ul><li>Protocol filtering bridges forward only packets of a certain type, i.e., token-ring or ethernet </li></ul></ul><ul><ul><li>Encapsulating bridges connect networks with different data link protocols, encapsulating messages with correct protocol for transmission </li></ul></ul><ul><ul><li>Layer-3 switches (IP switches) - can also switch messages based on their network layer address </li></ul></ul>
  34. 34. Shared Media Technologies <ul><li>Fast Ethernet </li></ul><ul><li>Fast Token Ring </li></ul><ul><li>Fiber Distributed Data Interface </li></ul>
  35. 35. Fast Ethernet <ul><li>100Base-X Ethernet </li></ul><ul><li>100VG-AnyLAN </li></ul><ul><li>Gigabit Ethernet </li></ul><ul><li>Iso-ENET (isochronous ethernet) </li></ul>
  36. 36. 100Base-X Ethernet <ul><ul><li>IEEE 802.13 </li></ul></ul><ul><ul><li>identical to 10Base-T Ethernet </li></ul></ul><ul><ul><li>three data link layer protocols </li></ul></ul><ul><ul><li>100 Mbps data rate </li></ul></ul><ul><ul><li>standard ethernet bus topology </li></ul></ul><ul><ul><li>ethernet data link packets </li></ul></ul><ul><ul><li>ethernet CSMA/CD media access protocol </li></ul></ul>
  37. 37. 100Base-X Ethernet <ul><li>Three versions of 100Base-X Ethernet </li></ul><ul><li>100Base-TX </li></ul><ul><li>100Base-FX </li></ul><ul><li>100Base-T4 </li></ul>
  38. 38. 100VG-AnyLAN <ul><li>IEEE 802.12 </li></ul><ul><li>both Ethernet or token-ring </li></ul><ul><li>Demand Priority Access Method (DPAM) polling </li></ul><ul><ul><li>polls each computer to see if it has data to send </li></ul></ul><ul><ul><li>can use a priority system (notification system) </li></ul></ul><ul><li>four sets of twisted pair running at 25 Mbps </li></ul><ul><li>faster than 100Base-T </li></ul>
  39. 39. Gigabit Ethernet <ul><li>IEEE 802.3Z </li></ul><ul><li>1000Base-X </li></ul><ul><li>1000 Mbps (1000 Mbps = 1 Gbps) </li></ul><ul><li>high speed of transmission may cause collisions to go undetected </li></ul><ul><li>mainly used for point-to-point full-duplex communication links (BN, MAN) </li></ul><ul><li>PCs send or receive data at rates up to 100 Mbps </li></ul>
  40. 40. Gigabit Ethernet <ul><li>Four versions of 1000Base-X Ethernet </li></ul><ul><ul><li>1000 Base-LX (fiber up to 440 meters) </li></ul></ul><ul><ul><li>1000 Base-SX (fiber up to 260 meters) </li></ul></ul><ul><ul><li>1000 Base-T (four pairs twisted-pair up to 100 meters) </li></ul></ul><ul><ul><li>1000 Base-CX (one cat 5 cable up to 24 meters) </li></ul></ul>
  41. 41. Iso-ENET <ul><li>IEEE 802.9A </li></ul><ul><li>isochronous Ethernet </li></ul><ul><li>standard 10Base-T Ethernet + 6.144 Mbps </li></ul><ul><li>both transmitted on the same twisted pair </li></ul><ul><li>6.144 circuit configured for ISDN for transmission of voice and video </li></ul><ul><li>mainly used for desktop videoconferencing and multimedia products </li></ul>
  42. 42. Fast Token Ring <ul><li>high-speed token ring (HSTR) </li></ul><ul><li>standard token ring topology </li></ul><ul><li>standard token ring protocols </li></ul><ul><li>token passing media access control </li></ul><ul><li>100 Mbps instead of 16 Mbps </li></ul><ul><li>category 5 or fiber optics cable </li></ul><ul><li>IBM working on 1 Gbps version </li></ul>
  43. 43. Fiber Distributed Data Interface (FDDI) <ul><li>ANSI X3T9.5 </li></ul><ul><li>Topology - token-passing </li></ul><ul><li>2 counter-rotating rings </li></ul><ul><li>Each ring operates at 100 Mbps over fiber optic cable </li></ul><ul><li>maximum of 1000 stations </li></ul><ul><li>distance 120 mile path (200k) </li></ul><ul><li>required repeaters to push transmission (2K) </li></ul><ul><li>data is usually carried on the primary ring </li></ul>
  44. 44. FDDI Station Types <ul><li>Dual-Attachment Station (DAS) </li></ul><ul><ul><li>connects to both primary and secondary rings </li></ul></ul><ul><ul><li>requires 4 fibers to the desk </li></ul></ul><ul><ul><li>allows the ring to continue to operate even if a break occurs in the line by rerouting through the secondary ring (backwards) </li></ul></ul><ul><li>Single-Attachment Station (SAS) </li></ul><ul><ul><li>connects only to the primary ring </li></ul></ul><ul><ul><li>requires 2 fibers to the desk </li></ul></ul>
  45. 45. FDDI Topology Primary Ring Secondary Ring FDDI Hub SAS SAS SAS Bridge Workstations Gateway Mainframe DAS DAS DAS DAS DAS
  46. 46. FDDI - How does it work? <ul><li>Media accesss control </li></ul><ul><ul><li>variation of token-passing standard </li></ul></ul><ul><ul><li>FDDI allows multiple messages to attach to the token - increases throughput above 100 Mbps </li></ul></ul><ul><li>An FDDI-to-IEEE 802.x bridge is required to connect to lower speed corporate LANs </li></ul><ul><li>At each node the optical signal is: </li></ul><ul><ul><li>converted to an electrical signal </li></ul></ul><ul><ul><li>amplified </li></ul></ul><ul><ul><li>copied (if necessary) </li></ul></ul><ul><ul><li>converted back to light to send to the next node </li></ul></ul>
  47. 47. Types of FDDI <ul><li>Basic FDDI previously discussed </li></ul><ul><li>FDDI-C (FDDI on Copper) </li></ul><ul><ul><li>Copper Distributed Data Interface (CDDI) </li></ul></ul><ul><ul><li>uses copper wire instead of fiber optic </li></ul></ul><ul><li>FDDI-II </li></ul><ul><ul><li>permits transmission of voice and video over the same cable as FDDI token-passing data </li></ul></ul><ul><ul><li>uses time division multiplexing </li></ul></ul><ul><ul><li>17 channels </li></ul></ul><ul><ul><ul><li>1 - 768 Kbps channel (token-passing) </li></ul></ul></ul><ul><ul><ul><li>16 - 6.144 Mbps channels (wide band - voice/video or data) </li></ul></ul></ul>
  48. 48. Switched Networks <ul><li>Switched Ethernet </li></ul><ul><li>Full-Duplex Ethernet </li></ul><ul><li>Switched Token Ring </li></ul><ul><li>Switched FDDI </li></ul><ul><li>Asynchronous Transfer Mode (ATM) </li></ul><ul><li>Fibre Channel </li></ul>
  49. 49. Switched Ethernet <ul><ul><li>the switch replaces the hub </li></ul></ul><ul><ul><li>creates a point-to-point circuit to the switch </li></ul></ul><ul><ul><li>allows multiple transmissions between computers </li></ul></ul><ul><ul><li>store-and-forward </li></ul></ul><ul><ul><li>improves LAN performance </li></ul></ul><ul><ul><li>circuit to the server is the network bottleneck </li></ul></ul>
  50. 50. Other Ethernet Solutions <ul><li>Full-Duplex Ethernet </li></ul><ul><ul><li>uses the same cables as regular Ethernet </li></ul></ul><ul><ul><li>10BaseT but full-duplex </li></ul></ul><ul><ul><li>doubles the speed of connections to 20 Mbps </li></ul></ul><ul><ul><li>full-duplex only from the switch to the server </li></ul></ul><ul><ul><ul><li>may have several connections to one server </li></ul></ul></ul><ul><li>10/100 switched ethernet </li></ul><ul><ul><li>combines 10BaseT and 100BaseT to the server </li></ul></ul><ul><ul><li>cheaper to install than 100Base-T </li></ul></ul><ul><ul><li>maybe as fast as fast ethernet </li></ul></ul>
  51. 51. Switched Token Ring <ul><ul><li>token ring switch replaces the token ring hub </li></ul></ul><ul><ul><li>provides a series of point-to-point connections </li></ul></ul><ul><ul><li>star topology </li></ul></ul><ul><ul><li>no token to pass because of full duplex switch </li></ul></ul><ul><ul><li>called “token-ring” because it uses token ring packet format and is compatible with 802.5 hardware </li></ul></ul><ul><ul><li>dedicated token ring (DTR) full duplex </li></ul></ul><ul><ul><li>32 Mbps data rate due to full duplex (16 Mbps each direction) </li></ul></ul>
  52. 52. Switched FDDI <ul><li>FDDI witch replaces the FDDI hub </li></ul><ul><li>point-to-point connctions to computers </li></ul><ul><li>star topology </li></ul><ul><li>no token because all computers can transmit and receive at will </li></ul><ul><li>same packet format and is fully compatible with other FDDI hardwar </li></ul>
  53. 53. ATM <ul><li>Isochronous networks provide very low and predictable node-to-node delays. They are capable of dealing with steady, immediate delivery, and high-bandwidth requirements of multimedia technology. </li></ul><ul><li>Asynchronous Transfer Mode (ATM) is the ultimate isochronous technology by allocating bandwidth on demand via virtual circuits. </li></ul><ul><ul><li>high-speed, hardware-based, circuit-switching technology </li></ul></ul><ul><ul><li>cell-relay </li></ul></ul><ul><ul><li>LANE (LAN Emulation/LAN Encapsulation) </li></ul></ul><ul><ul><li>connection-oriented </li></ul></ul><ul><ul><li>ATM desktop - point-to-point full duplex - “low speed” version for the desktop </li></ul></ul>
  54. 54. ATM <ul><li>ATM is a switched network but differs from switched ethernet and switched token ring in four ways: </li></ul><ul><ul><li>1. ATM uses fixed-length packets of 53 bytes ( ATM encapsulation) </li></ul></ul><ul><ul><li>2. no error correction on the user data </li></ul></ul><ul><ul><li>3. ATM uses a very different type of addressing from traditional data link layer protocols such as ethernet or token ring </li></ul></ul><ul><ul><li>4. ATM prioritizes transmissions based on Quality of Service (QoS). </li></ul></ul>
  55. 55. Asynchronous Transfer Mode (ATM) <ul><li>Asynchronous Transfer Mode is connection-oriented so all packets travel in order through the virtual circuit. A virtual circuit can either be a: </li></ul><ul><li>Permanent Virtual Circuit (PVC) - defined when the network is established or modified. </li></ul><ul><li>Switched Virtual Circuit (SVC) - defined temporarily for one transmission and deleted with the transmission is completed. </li></ul>
  56. 56. LAN Translation <ul><li>two approaches for translation </li></ul><ul><ul><li>LANE (LAN Emulation/LAN Encapsulation) </li></ul></ul><ul><ul><li>Multiprotocol over ATM (MPOA) </li></ul></ul>
  57. 57. LAN Encapsulation <ul><li>usually referred to as LAN Emulation </li></ul><ul><li>data link layer packets left intact; broken down and encapsulated </li></ul><ul><li>reassembled on the LAN side </li></ul><ul><li>LAN thinks that the packets are token ring or Ethernet </li></ul><ul><li>requires ATM edge switches at each side </li></ul>
  58. 58. Multiprotocol over ATM <ul><li>extension of LANE </li></ul><ul><li>uses network layer addresses and data link layer addresses </li></ul><ul><li>destination determines which address to use </li></ul><ul><li>route servers required (MPOA servers) </li></ul>
  59. 59. ATM to the Desktop <ul><li>ATM-25 is a low speed version of ATM which provides point-to-point full duplex circuits at 25.6 Mbps in each direction. It is an adaptation of token ring that runs over cat 3 cable and can even use token ring hardware if modified. </li></ul><ul><li>ATM-51 is another version designed for the desktop allowing 51.84 Mbps from computers to the switch. </li></ul>
  60. 60. ATM Classes of Service <ul><li>ATM provides five classes of service: </li></ul><ul><ul><li>Constant Bit Rate (CBR) </li></ul></ul><ul><ul><li>Variable Bit Rate-Real Time (VBR-RT) </li></ul></ul><ul><ul><li>Variable Bit Rate-Non-Real Time (VBR-NRT) </li></ul></ul><ul><ul><li>Available Bit Rate (ABR) </li></ul></ul><ul><ul><li>Unspecified Bit Rate (UBR) </li></ul></ul>
  61. 61. Fiber Channel <ul><li>Fiber channel is relatively new networking technology, although it has been used inside computer and disk storage devices for several years. </li></ul><ul><li>Fiber channel was originally designed to provide high speed transmission over fiber optic cable. The maximum data rate is 1.062 Gbps up to 10 k with higher rates under development. </li></ul>
  62. 62. Improving Backbone Performance <ul><li>change network protocol </li></ul><ul><li>check impact of applications </li></ul><ul><li>replace the hubs with switches and make point-to-point connections available </li></ul><ul><li>increase circuit capacity </li></ul><ul><li>make sure BN devices have sufficient memory, so packets don’t get lost and have to be resent </li></ul>
  63. 63. Improving Backbone Performance <ul><li>use faster routing protocol </li></ul><ul><li>upgrade computers that perform routing </li></ul><ul><li>use switches from a single vendor </li></ul><ul><li>eliminate need for switch-to-switch routing by use of collapsed backbone switch </li></ul>
  64. 64. Collapsed Backbone Networks <ul><li>uses point-to-point circuits when possible </li></ul><ul><li>uses a switch and a set of circuits to each LAN </li></ul><ul><li>uses more cable, but fewer devices </li></ul><ul><li>“backbone” exists in the switch </li></ul><ul><li>improved performance </li></ul><ul><li>switch replaces multiple bridges or routers </li></ul><ul><li>lowers costs </li></ul><ul><li>simplifies network management </li></ul><ul><li>if the switch fails, the network is down </li></ul>
  65. 65. Improving Circuit Capacity <ul><li>increase overall circuit capacity or place additional circuits alongside heavily used circuits </li></ul><ul><li>move from shared circuit to switched circuit BN </li></ul><ul><li>increase capacity to the server </li></ul>
  66. 66. How much bandwidth to expect LAN Type Speed Ethernet 10 Mbps Token Ring 16 Mbps Fast Ethernet 100 Mbps Faster Ethernet 1 Gbps Fast Token Ring 100 Mbps FDDI 100 Mbps ATM 2.4 Gbps Improving Circuit Capacity
  67. 67. Reduce Network Demand <ul><li>restrict high-bandwidth applications: </li></ul><ul><ul><li>video conferencing </li></ul></ul><ul><ul><li>medical imaging </li></ul></ul><ul><ul><li>multimedia </li></ul></ul><ul><li>set routing devices to filter broadcast messages </li></ul>
  68. 68. Selecting a Backbone Network <ul><li>5 important factors to consider: </li></ul><ul><li>Throughput </li></ul><ul><li>Network cost </li></ul><ul><li>Type of application </li></ul><ul><li>Ease of network management </li></ul><ul><li>Compatibility with current and future technologies </li></ul>