Transcript MIS 430 – Chapter 7 - Remote Desktop Web Connection

MIS 430 – Chapter 8
Backbone Networks
Chapter 8: Backbone Networks
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Overview
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Backbone networks connect LANs and
also link BNs to WANs
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BNs connect networks
Can be called a campus network or an
enterprise network
Technology is different – typically ATM
or fiber
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Much higher speed circuits than most LANs
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I. Backbone Network
Components
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BN Components
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Network cable
Hardware Devices
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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
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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
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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
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Ex: connect TCP/IP to IBM SNA protocol
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Think “dissimilar” networks 
Gateway must transform message to make it look
like it came from other network
See Figure 8-4 p. 260:
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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…
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Industry jargon may differ from the
definitions in chapter 8
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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
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Basic Types
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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
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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
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Former ISU technology – see fig 8-6 p 265
Advantages
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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
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Routers introduce time delay
This requires lots of management
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Bridged Backbone
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Similar design, see fig 8-7 p. 267 but all on
same subnet
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Disadvantages (really not used on new
networks)
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Major performance problems
All LANs must have same DLL protocol
A change in one LAN can affect other LANs
Advantages
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Simpler, easier to install, less expensive
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Collapsed Backbone - ISU
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Most common for new nets, fig 8-8 p. 268
Advantages
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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
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Use more cable, run longer distances (fiber)
If core switch fails, so does entire BN!
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Rack-Based Collapsed Backbones
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Most organizations use 19” rack mount
devices: see fig 9,10 p. 270-1 (HP gear)
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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
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Can use a chassis switch instead of a rack
Plug in modules to represent a network
device
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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
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See fig 8-11, p. 273: collapsed
backbone
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Virtual LAN (VLAN)
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Separate the physical subnets from the logical
subdivisions (we do this at ISU)
Computers are assigned to subnets by
software rather than hardware
Advantages
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Faster, more flexible
Easier to manage flow of traffic than previous
Disadvantage: more complex, for large
networks
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More on VLANs
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Single Switch VLAN
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See fig 8-12, p. 274
Everything is inside one switch
Looks like computers are linked through
hubs
Multiswitch VLAN
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Fig 8-13. P 276
Multiple switches are involved
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FDDI-Fiber Distributed Data Interface
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Originally for MANs, now in backbones
Ring topology, 100 Mbps, up to 200 km
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Primary ring
Secondary ring (backup)
CDDI is just like FDDI but uses copper
Cat 5 cable
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ATM - Async Transfer Mode
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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
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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
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Similar to LANs: find the bottleneck
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Eliminating the bottleneck generally means
moving it elsewhere, so this is iterative
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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
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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)
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Increase Circuit Capacity
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Go from 100BaseT to Gigabit Ethernet
Buy additional circuits alongside existing
Replace shared circuit backbone with
switched circuit backbone
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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
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Restrict high bandwidth applications
(video conferencing or multimedia)
Reduce broadcast messages
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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
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New technologies (ATM, gigabit Ethernet)
New architectures (collapsed backbones,
VLANs)
Today’s best
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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
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http://misnt.indstate.edu/bjm/itroom/
You will see
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Monitoring stations
Rack-mount servers
Stand-alone servers
Blade server
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