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48 Chapter 2: Business and Technical Requirements
Today's internetworks are becoming increasingly congested and overworked. In addition to an
ever-growing population of network users, several factors have combined to put stress on the
capabilities of traditional LANs:
·
Faster CPUs--In the mid-'80s, the most common desktop workstation was a PC. At the
time, most PCs could execute one million instructions per second (MIPS). Today,
workstations with 500­750 MIPS of processing power are common, and I/O speeds have
increased accordingly. Two modern engineering workstations on the same 10 Mbps LAN
can easily saturate it.
·
Faster operating systems--During the first generation of network design, operating
systems had limited network access. Of the three most common desktop operating
systems, only UNIX could allow users to initiate simultaneous network transactions. With
the release of Microsoft Windows, PC users could multitask, create peer-to-peer networks,
and increase their demands for network resources. Presently, most network users are
expected to depend on the WAN as their primary source of resources.
·
Network-intensive applications--Use of client/server applications is now more the
norm than the exception. The CCDP should expect his users to obtain 80 percent of their
applications or data from a remote server or network. Client/server applications allow
administrators to centralize information, thus making it easy to maintain and protect.
Client/server applications free users from the burden of maintaining information and the
cost of providing enough hard disk space to store it. Given the cost benefit of client/server
applications, such applications are likely to become even more widely used in the future.
Campus VLAN Design
The first step in campus network design is to identify the business and technical requirements.
The primary objective of a network design is to ensure efficient delivery of the right information
at the right time to the right person. The determination of what information has preference on
the network and which users have network access priority must be defined by the business
requirements.
To overcome the bandwidth limitations and shortcomings of the router and hub design, many
designers embraced the campus VLAN design. Today's applications are designed to be more
powerful. More power demands more network horsepower. The campus VLAN design provides
additional bandwidth, giving users a dedicated 10 or 100 Mbps to the server. A VLAN isolates
bandwidth segments. Therefore, one user or a group of users who require large amounts of
bandwidth will not impact network performance for the rest of the network. The development
of Layer 2 switching in hardware several years ago led to network designs that emphasized
Layer 2 switching.
87200333.book Page 48 Wednesday, August 22, 2001 2:18 PM