Chapter 8: Backbone Networks1 MIS 430 – Chapter 8 Backbone Networks.

Chapter 8: Backbone Networks

1

MIS 430 – 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


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


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


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


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


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.


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


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


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


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


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!


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


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


15

Mgt Focus 8-2 Central Parking

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


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


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


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


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)


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


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)


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)


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?


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


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 Networks1 MIS 430 – Chapter 8 Backbone Networks.

Documents

Transcript of Chapter 8: Backbone Networks1 MIS 430 – Chapter 8 Backbone Networks.