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In today's networks, traffic patterns are moving
toward what is now referred to as the 20/80 model as shown in the
Figure. In the 20/80 model, only 20 percent of traffic remains local
to the workgroup LAN, and 80 percent of the traffic leaves the local
network.
Two factors have contributed to these changing
traffic patterns:
- The Internet - With Web-based
computing and Internet applications, a PC can be a tool for both
publishing and accessing information. So information can now
come from anywhere in the network, potentially creating massive
amounts of traffic crossing subnet boundaries. Users hop
transparently between servers across the enterprise by using
hyperlinks, without having to worry about where the data is
located.
- Server farms - The second factor
leading to the decline of local-centric networks is the move
toward server consolidation. Enterprises are deploying
centralized server farms for the security, ease of management,
and reduced cost of ownership. All traffic from the client
subnets to these servers must travel across the campus backbone.
However, this change in traffic patterns
requires the Layer 3 performance to approximate the Layer 2
performance. Because routing is a CPU-intensive process, this Layer
3 processing can create network bottlenecks. This, in a nutshell, is what drives the
continued increase in requirements on campus networks.
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