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Foundation Topics 47
Foundation Topics
In the early days of local-area networking, campus LANs consisted of thick or thin Ethernet or
star-wired Token Ring. In the late '80s and early '90s, networks adopted unshielded twisted-
pair (UTP) as the LAN cabling standard. A typical cabling infrastructure consisted of UTP
cabling to the desktop and multimode fiber in the backbone. As networks continued to grow and
user applications continued to demand more bandwidth, something had to be done about
controlling the extra traffic. Bridges were developed to segment traffic and minimize
congestion. Routers and switches were introduced to isolate broadcast traffic and to allow better
traffic-flow management. With the addition of Apple's and Novell's operating systems to the
network arena, AppleTalk and IPX protocols were introduced to the network environment. As
you will see, each protocol brings different challenges to the issues of network traffic
management. As the needs of users and applications continue to evolve, so will the issues of
campus LAN design. See Figure 2-2.
Figure 2-2
Change from Shared to Switched Networks
No matter what the size of the current network, there is one thing the CCDP should always
expect: change. As the customer grows and changes, so will the demands placed on the network.
Users will move to different locations. Branches will relocate to different cities. Business and
Web applications will become more powerful and demanding. Changing business and technical
requirements mandate that flexibility be a primary requirement of internetwork design.
CDDI/FDDI
concentrator
Shared hub
Traditional wiring closet
Traditional backbone
Cisco router
Hub
The new wiring closet
Shared hub
LAN switch (Layer 2)
Multilayer switch
(Layers 2 and 3)
ATM campus
switch
Cisco router
The new backbone
87200333.book Page 47 Wednesday, August 22, 2001 2:18 PM