Computer network topologies

Another way to categorize computer networks is by their topology, or the way in which hosts and nodes are arranged and connected to one another, and how they communicate. The computer network mainly recognizes two types of topologies: physical, and logical.

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Physical topology

Physical topology presents ordering, arrangement, and placement of the physical parts of a computer network, such as computers, peripheral devices, cables for data transmission, and network equipment. Thus, the physical topology of the computer network actually represents its physical structure, which is usually presented in the following shapes: bus, ring, star, extended star, hierarchical, and mesh.

Bus

Bus is the physical topology in which computers, peripheral and network devices are connected through the bus that mainly consists of a coaxial cable (see Figure 1.5):

Figure 1.5. Bus physical topology

Ring

Ring is the physical topology in which computers, peripheral and network devices form a closed cycle that takes the shape of a ring network where each device is connected to each other (see Figure 1.6). In the past, the coaxial cable was used, but nowadays in dual ring networks, optical fiber is used:

Figure 1.6. Ring physical topology

Star

Star is the physical topology in which computers, peripheral and network devices are connected independently with a central device (see Figure 1.7). For this type of topology, mainly a twisted pair cable is used:

Figure 1.7. Star physical topology

Extended star

Extended star is the physical topology in which computers and peripheral and network devices are connected into two or more star topology networks and then the central components (that is, switches) are interconnected over a bus. In appearance, this type of topology combines star and bus topologies (see Figure 1.8). Mainly, a twisted cable pair is used for the star topology, while an optical fiber is used for the bus topology:

Figure 1.8. Extended star physical topology

Hierarchical

Hierarchical is the physical topology that represents a combination of star and bus topologies. This topology must have at least three levels of hierarchy in which star topologies connect one or more nodes to a single main node, so that all these together are related to the main trunk of the tree (see Figure 1.9). As in the case of an extended star topology, this topology uses twisted pair cables and optical fiber:

Figure 1.9. Hierarchical physical topology

Mesh

Mesh is the physical topology in which each computer is connected with every computer to form the network (see Figure 1.10). Usually, this type of topology is utilized by a WAN to interconnect LANs:

Figure 1.10. Mesh physical topology

Logical topology

Unlike physical topology, logical topology represents the logical aspect of the computer network. In logical topology, it is the logical paths that are used to carry electric or light signals from one computer to another, or from one network node to another node. Thus, this topology represents the way in which the data accesses the transmission medium and transmits packets through it. Figure 1.11 presents the logical topology with its logical components such as computer names, network equipment, network communication technology, and IP addresses:

Figure 1.11. Logical topology