3 Topology

Bus Topology

Bus networks use a common backbone for all devices/hosts on the network. The backbone is essentially a single cable that serves as a shared communication medium. In order for one host to communicate with another host they send a broadcast request (part of the Ethernet layer 2 specification) that is received by all hosts/devices, and the intended recipient accepts, processes and responds to the message.

One of the benefits of a bus topology is that it is relatively simple to install and generally requires less cable than other topologies. Cable types for bus topologies include RG58 for 10Base-2 Ethernet, which is also known as "ThinNet" (and provides a range of up to 180 feet). The cable type typically used as a backbone is a special type that is similar to RG8U and designed for 10Base-5 Ethernet, also known as "ThickNet" (provides a range of up to 500 feet). The drawbacks of bus topologies include limitations on the number of devices that are supported, difficulty working with stiff coax cable, and if the backbone cable fails, the entire network becomes unusable.

Ring Topology

In a ring network, all messages travel through a ring in the same direction (either "clockwise" or "counterclockwise"). Cables used in ring topologies vary widely but usually consist of fiber optics (FDDI networks) or type 1, type 3 or CAT3 for Token Ring. Likewise, network range can vary from hundreds of feet to several miles (as is the case with FDDI). Unlike bus and star topologies (which typically use Ethernet at layer 2), ring topologies typically use a layer two protocol that manages communication on the network by passing a “token” from device to device. The device that currently has the “token” is the only device allowed to send messages. Ring topologies typically have some form of redundancy to overcome a device or cable failure because a break the ring and can cause the entire network to fail. For example, FDDI is a ring topology that consists of two rings that...