The connected computer network elements may be each independently
connected on the network or connected in small clusters, which are in turn
connected together to form bigger networks via connecting devices. The size
of the clusters determines the network type. There are, in general, two network
types: a local area network (LAN) and a wide area network (WAN). A LAN
consists of network elements in a small geographical area such as a building
floor, a building, or a few adjacent buildings. The advantage of a LAN is that
all network elements are close together so the communication links maintain
a higher speed data movement. Also, because of the proximity of the communicating elements, high- cost and quality communicating elements can be used
to deliver better service and higher reliability. Figure 5.1 shows a LAN network.
WANs cover large geographical areas. Some advantages of a WAN
5—Cyberspace Infrastructure 33
include the ability to distribute services to a wider community and the availability of a wide array of both hardware and software resources that may not
be available in a LAN. However, because of the large geographical areas covered by WANs, communication media are slow and often unreliable. Figure
5.2 shows a WAN network.
WAN networks are typically found in two topologies: mesh and tree.
WANs using a mesh topology provide multiple access links between network
elements. The multiplicity of access links offers an advantage in network reliability because whenever a network element failure occurs, the network can
always find a bypass to the failed element and the network continues to function. Figure 5.3 shows a mesh network.
A WAN using a tree topology uses a hierarchical structure in which the
most predominant element is the root of the tree and all other elements in the
network share a child- parent relationship. The tree topology is a generalization
of the bus topology. As in ordinary trees, there are no closed loops, so dealing
with failures can be tricky, especially in deeply rooted trees. Transmission from
any element in the network propagates through the network and is received
by all elements in the network. Figure 5.4 shows a WAN using a tree topology.
34 Computer Network Security and Cyber Ethics
Figure 5.1 A LAN N