MIS 430 – Chapter 8

Backbone Networks Chapter 8: Backbone Networks 1

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 2

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I. Backbone Network Components

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

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 4

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 5

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 6

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.

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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 Chapter 8: Backbone Networks 8

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 9

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 10

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 11

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 Chapter 8: Backbone Networks 13

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 14

Mgt Focus 8-2 Central Parking

 See fig 8-11, p. 273: collapsed backbone Chapter 8: Backbone Networks 15

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 16

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 17

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 18

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 19

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 20

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 21

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 22

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) 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 24

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 25