Computer Network Topology

More and more computer networks use wireless methods to move data from one system to another, however many networks still use some type of cabling (Copper or Fiber Optic) to connect systems. The way that cable and hardware, or wireless signals connect to one another to form a network is known as the Network Topology. Historical network topologies include Bus, Ring, and Star, while modern topologies include Hybrid, Mesh, Point-to-Multipoint, and Point-to-Point.

Historical Topologies

Bus: A bus topology uses a single bus cable that connects all of the computers in a line, and data goes out on the entire bus. To prevent data from reflecting at the ends of the cable and creating unnecessary traffic a bus topology needs terminators at each end of the cable.

Ring: A ring topology is similar to a bus topology except that it connects all computers with a central ring cable, so there are no ends to the bus and it does not require termination. The data flows in a circle from one computer to the next in the same direction.

*If a cable is broken at any point in a bus or ring topology the entire network stops working. The broken ends in a bus topology creates reflection of data between the still connected computers because the termination point is no longer connected to the network. A broken cable in a ring topology breaks the circuit and stops the flow of data.

Star: A star topology uses a central connection point for all computers on a network, which offers fault tolerance not available with bus or ring topologies. If any one connection is broken in a star topology the other systems on the network are not affected and are still able to send and receive data.

Modern Topologies

Hybrid: A hybrid topology combines the features of the bus and ring topologies with the star topology by shrinking the actual bus or ring into a small box called a hub which serves the purpose of the central connection point or star. Star-bus and star-ring topologies physically look like star topologies however the actual electronic schematics act like a bus or ring. Any topology that combines a physical topology with an electronic signalling topology is known as a Hybrid Topology.

Mesh: A mesh topology connects every system to every other system in a network via two or more routes, sometimes requiring particular routes to traverse through another system in the mesh network. A partially meshed topology includes at least two systems with redundant connections, and every computer does not need to connect to every other computer. In a fully meshed topology every computer connects directly to every other computer. A meshed topology is very robust and if a single connection is broken the systems are not affected, however because of the complexity of connecting cables to and from every computer in a network the mesh topology is not practical for cabled networks and will usually only be seen in wireless networks.

Point-to-Multipoint: A point-to-multipoint topology includes a single computer system that is used a common source through which all of the other systems on the network converse. Similar to the star topology in that there is a central point, the difference is in the device that exists in the center of the network. The center of the star topology is little more than a path for the data to travel to the various systems, whereas the center of a point-to-multipoint topology includes an actual hub, router, or switch which controls the data flow to the various other systems in the network. The point-to-multipoint topology is sometimes referred to as a Tree Topology and is known as an Infrastructure Network.

Point-to-Point: A point-to-point topology includes two computers directly connected together with no need for a central hub, router, or switch. Point-to-point topologies are found in both wired and wireless networks. They are known as Ad-hoc or Peer to Peer networks.

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