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MIS 430 – Chapter 8

MIS 430 – Chapter 8. Backbone Networks. Overview. Backbone networks connect LANs and also link BNs to WANs BNs connect networks Can be called a campus network or an enterprise network Technology is different – typically ATM or fiber Much higher speed circuits than most LANs.

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MIS 430 – Chapter 8

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  1. MIS 430 – Chapter 8 Backbone Networks Chapter 8: Backbone Networks

  2. Overview • Backbone networks connect LANs and also link BNs to WANs • BNs connect networks • Can be called a campus network or an enterprise network • Technology is different – typically ATM or fiber • Much higher speed circuits than most LANs Chapter 8: Backbone Networks

  3. I. Backbone Network Components • BN Components • Network cable • Hardware Devices • Bridges: connect two or more network segments that use the same data link and network protocol • Routers: connect 2 or more network segments with same or different data link protocols but same network protocols • Gateways: connect 2 or more network segments with same or different data link and network protocols Chapter 8: Backbone Networks

  4. Bridges • Understand only data link protocols and addresses • May connect same or different types of cable • As switches were introduced, bridges have become obsolete Chapter 8: Backbone Networks

  5. Routers • May connect same or different cable types • Routers are “TCP/IP gateways” of ch. 6 • Router processes only those messages directed toward it • Router learns best routes by building routing table Chapter 8: Backbone Networks

  6. Gateways • Ex: connect TCP/IP to IBM SNA protocol • Think “dissimilar” networks  • Gateway must transform message to make it look like it came from other network • See Figure 8-4 p. 260: • TCP/IP LAN (ASCII) • Token ring LAN • IBM Mainframe (EBCDIC) • Gateway avoids having to install SNA HW/SW on each client that wants to talk to mainframe Chapter 8: Backbone Networks

  7. A Caveat from Dr. Dennis… • Industry jargon may differ from the definitions in chapter 8 • One vendor’s bridge may do router functions • Multiprotocol routers (TCP/IP and IPX/SPX) are gateways • Brouters combine functions of bridges and routers • Layer-3 switches provide both switch and router functions (but are much faster than routers) … we use Cisco layer-3 switches instead of routers now. Chapter 8: Backbone Networks

  8. II. Backbone Network Architectures • Basic Types • Routed backbone (use NL addresses) • Bridged backbone (use DLL addresses) • Collapsed backbone (switches using DLL addresses) • Virtual LANs (switches moving packets through virtual but not physical LANs) • Can be mixed and matched Chapter 8: Backbone Networks

  9. Backbone Architecture Layers • Access layer (e.g., 10BaseT) – actually part of LAN, but affects BN speeds • Distribution layer – part that connects the LANs together • Core layer – part that connects BNs together Chapter 8: Backbone Networks

  10. Routed Backbone • Former ISU technology – see fig 8-6 p 265 • Advantages • It clearly segments each part of network, each with own subnet address • LANs separated, can have different protocols • Users can access own server or others easily • Disadvantages • Routers introduce time delay • This requires lots of management Chapter 8: Backbone Networks

  11. Bridged Backbone • Similar design, see fig 8-7 p. 267 but all on same subnet • Disadvantages (really not used on new networks) • Major performance problems • All LANs must have same DLL protocol • A change in one LAN can affect other LANs • Advantages • Simpler, easier to install, less expensive Chapter 8: Backbone Networks

  12. Collapsed Backbone - ISU • Most common for new nets, fig 8-8 p. 268 • Advantages • Improved performance due to core switch allowing simultaneous access from LANs • Fewer networking devices: lower cost and network mgt is simpler, done in one place • Disadvantages • Use more cable, run longer distances (fiber) • If core switch fails, so does entire BN! Chapter 8: Backbone Networks

  13. Rack-Based Collapsed Backbones • Most organizations use 19” rack mount devices: see fig 9,10 p. 270-1 (HP gear) • All devices located in same room • MDF (main distribution facility) or CDF (central distribution facility) • Cables enter from back, are routed in front • Can move clients from one router to another to load balance Chapter 8: Backbone Networks

  14. Chassis-Based Collapsed Backbone • Can use a chassis switch instead of a rack • Plug in modules to represent a network device • 16 port 10BaseT hub • Router • 4-port 100BaseT hub, etc. • Key: flexibility and cost is less than rack mount Chapter 8: Backbone Networks

  15. Mgt Focus 8-2 Central Parking • See fig 8-11, p. 273: collapsed backbone Chapter 8: Backbone Networks

  16. Virtual LAN (VLAN) • Separate the physical subnets from the logical subdivisions (we do this at ISU) • Computers are assigned to subnets by software rather than hardware • Advantages • Faster, more flexible • Easier to manage flow of traffic than previous • Disadvantage: more complex, for large networks Chapter 8: Backbone Networks

  17. More on VLANs • Single Switch VLAN • See fig 8-12, p. 274 • Everything is inside one switch • Looks like computers are linked through hubs • Multiswitch VLAN • Fig 8-13. P 276 • Multiple switches are involved Chapter 8: Backbone Networks

  18. FDDI-Fiber Distributed Data Interface • Originally for MANs, now in backbones • Ring topology, 100 Mbps, up to 200 km • Primary ring • Secondary ring (backup) • CDDI is just like FDDI but uses copper Cat 5 cable Chapter 8: Backbone Networks

  19. ATM - Async Transfer Mode • Originally for WANs, now also in BNs • Topology: point to point full duplex @ 155 Mbps (310 Mbps in half duplex) or 622 Mbps • Originally designed for fiber, now on Cat 5e • ATM differs from switched Ethernet • Fixed length packets (53 bytes) – fast switching • No error correction of user data • Different addressing: virtual channel, not fixed • ATM prioritizes transmissions based on basis of QoS – 5 classes of service in ATM (voice is highest priority) Chapter 8: Backbone Networks

  20. III. Improving Backbone Performance • Similar to LANs: find the bottleneck • Eliminating the bottleneck generally means moving it elsewhere, so this is iterative • Speed up computers on the network • Speed u pother device on the network • Upgrade circuits between computers • Change the demand placed on the network Chapter 8: Backbone Networks

  21. Improve Computers/Devices • Buy faster devices (routers and switches) • Change to a more appropriate routing protocol (static usually or dynamic) • Buy devices and SW from one vendor (C!) • Reduce translation between different protocols • Increase the device’s memory (because devices are store and forward) Chapter 8: Backbone Networks

  22. Increase Circuit Capacity • Go from 100BaseT to Gigabit Ethernet • Buy additional circuits alongside existing • Replace shared circuit backbone with switched circuit backbone • Replace Ethernet with switched Ethernet • Usually OK to have 10 Mbps to desktops but a faster circuit to the server (e.g. 807) Chapter 8: Backbone Networks

  23. Reduce Network Demand • Restrict high bandwidth applications (video conferencing or multimedia) • Reduce broadcast messages • looking for data link layer addresses • Some NOS ask for status of computers on net • Filter broadcast messages outside of LAN • Time shift the demand  flextime? Chapter 8: Backbone Networks

  24. IV. Best Backbone Practice • New technologies (ATM, gigabit Ethernet) • New architectures (collapsed backbones, VLANs) • Today’s best • Ethernet-based collapsed backbone with Switched Ethernet in LAN • Gigabit Ethernet will probably replace ATM, FDDI at BN Chapter 8: Backbone Networks

  25. ISU Machine Room Photos • http://misnt.indstate.edu/bjm/itroom/ • You will see • Monitoring stations • Rack-mount servers • Stand-alone servers • Blade server Chapter 8: Backbone Networks

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