MIS 430

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MIS 430 Chapter 8

• Backbone Networks

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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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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

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Bridges

• Understand only data link protocols and addresses
• May connect same or different types of cable
• As switches were introduced, bridges have become
  obsolete

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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

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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

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A Caveat from Dr. Dennis

• Industry jargon may differ from the definitions
  in chapter 8
• One vendors 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.

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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

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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

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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

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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

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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!

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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

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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

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Mgt Focus 8-2 Central Parking

• See fig 8-11, p. 273 collapsed backbone

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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

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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

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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

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ATM - Async Transfer Mode

• Originally for WANs, now also in BNs
• Topology point to point full duplex _at_ 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)

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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

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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 devices memory (because devices are
  store and forward)

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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)

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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?

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IV. Best Backbone Practice

• New technologies (ATM, gigabit Ethernet)
• New architectures (collapsed backbones, VLANs)
• Todays best
• Ethernet-based collapsed backbone with Switched
  Ethernet in LAN
• Gigabit Ethernet will probably replace ATM, FDDI
  at BN

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ISU Machine Room Photos

• http//misnt.indstate.edu/bjm/itroom/
• You will see
• Monitoring stations
• Rack-mount servers
• Stand-alone servers
• Blade server