Peerto Peer Topology

A peer-to-peer WAN can be developed using leased private lines or any other transmission facility. This WAN topology is a relatively simple way of interconnecting a small number of sites. WANs that consist of just two locations can only be interconnected in this manner. Figure 13-1 depicts a small, peer-to-peer

This topology represents the least-cost solution for WANs that contain a small number of internetworked locations. Because each location contains, at most, one or two links to the rest of the network, static routing can be used. Static routing can be time intensive to establish but avoids the network overheads of dynamic routing protocols. Given that there aren't any redundant routes to be had in this simple topology, the benefits of dynamic routing are obviated. This fundamental lack of route redundancy must be considered an inescapable limitation of this topology.

Unfortunately, peer-to-peer WANs also suffer from two other limitations. First, they do not scale very well. As additional locations are introduced to the WAN, the number of hops between any given pair of locations remains highly inconsistent and trends upward. This results in varied levels of performance in communications between any given pair of locations. The actual degree to which performance varies depends greatly on many factors, including the following:

• Type and capacity (bandwidth) of transmission facility

• Degree to which the transmission facility is being utilized

• Geographic distances between locations

The degree to which this lack of scalability will affect your internetwork depends directly on how big you expect it could get. If your particular situation is such that it is extremely unlikely that your internetwork will ever grow beyond a handful of locations, this may well be the ideal topology.

The second limitation of this approach is its inherent vulnerability to component failure. There is only a single path between any given pair of locations. Consequently, an equipment or facility failure anywhere in a peer-to-peer WAN can split the WAN. Depending on the actual traffic flows and the type of routing

WAN.

Figure 13-1: A peer-to-peer WAN constructed with leased lines.

Figure 13-1: A peer-to-peer WAN constructed with leased lines.

Building Internetworks implemented, this can severely disrupt communications in the entire WAN.

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