Chapter 8: Backbone Networks1 MIS 430 – Chapter 8 Backbone Networks.
-
Upload
alannah-harrington -
Category
Documents
-
view
242 -
download
3
Transcript of Chapter 8: Backbone Networks1 MIS 430 – Chapter 8 Backbone Networks.
Chapter 8: Backbone Networks
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