Information Technology Reference
In-Depth Information
Figure 2-16
Full-Mesh Network: Every Router Has a Link to Every Other Router in the
Network
A full-mesh network can be expensive to implement in WANs because of the required
number of links. In addition, groups of routers that broadcast routing updates or service
advertisements have practical limits to scaling. As the number of routing peers increases,
the amount of bandwidth and CPU resources devoted to processing broadcasts increases.
A suggested guideline is to keep broadcast traffic at less than 20 percent of the band-
width of each link; this amount limits the number of peer routers that can exchange rout-
ing tables or service advertisements. When designing for link bandwidth, reserve 80
percent of it for data, voice, and video traffic so that the reset can be used for routing and
other link traffic. When planning redundancy, follow guidelines for simple, hierarchical
design. Figure 2-17 illustrates a classic hierarchical and redundant enterprise design that
uses a partial-mesh rather than a full-mesh topology. For LAN designs, links between the
access and distribution layer can be Fast Ethernet, with links to the core at Gigabit Ether-
net speeds.
Headquarters
1.5 Mbps
Regions
128 Kbps
Branches
Figure 2-17
Pa r t i a l -Me s h D e s i g n w i t h R e d u n d a n c y
