Ring Topology

Star-Wired Ring

A star-wired ring topology may appear (externally) to be the same as a star topology. Internally, the MAU (multistation access unit) of a star-wired ring contains wiring that allows information to pass from one device to another in a circle or ring The Token Ring protocol uses a star-wired ring topology.

RING - TOPOLOGY

A system of local area networking in which each node or station is connected to two others, ultimately forming a loop. Data are passed in one direction only, being received by each node and then transferred to the next node. Access is achieved either by means of a token, passed from one node to the other, or by polling, a kind of inquiry made by a master station. Also known as a ring network.

A double ring that consists of two independent rings, a primary and a secondary, with traffic flowing in opposite directions. A computer that is connected to both rings is called a dual attachment station (DAS), and when one of the rings is broken by a cable fault, the computer switches to the other ring, providing continued full access to the entire network. The double ring is suited to use as a backbone network.

Ring Topology is called Tree topology. More information given below -----

A tree topology combines characteristics of linear bus and ring topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable . Ring allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.

Advantages of a Ring Topology

• Point-to-point wiring for individual segments.
• Supported by several hardware and software venders.

Disadvantages of a Ring Topology

• Overall length of each segment is limited by the type of cabling used.
• If the backbone line breaks, the entire segment goes down.
• More difficult to configure and wire than other topologies.

5-4-3 Rule

A consideration in setting up a tree topology using Ethernet protocol is the 5-4-3 rule. One aspect of the Ethernet protocol requires that a signal sent out on the network cable reach every part of the network within a specified length of time. Each concentrator or repeater that a signal goes through adds a small amount of time. This leads to the rule that between any two nodes on the network there can only be a maximum of 5 segments, connected through 4 repeaters/concentrators. In addition, only 3 of the segments may be populated (trunk) segments if they are made of coaxial cable. A populated segment is one which has one or more nodes attached to it . In Figure 4, the 5-4-3 rule is adhered to. The furthest two nodes on the network have 4 segments and 3 repeaters/concentrators between them.

This rule does not apply to other network protocols or Ethernet networks where all fiber optic cabling or a combination of a fiber backbone with UTP cabling is used. If there is a combination of fiber optic backbone and UTP cabling, the rule is simply translated to 7-6-5 rule.

Considerations When Choosing a Topology:

• Money. A linear bus network may be the least expensive way to install a network; you do not have to purchase concentrators.
• Length of cable needed. The linear bus network uses shorter lengths of cable.
• Future growth. With a star topology, expanding a network is easily done by adding another concentrator.
• Cable type. The most common cable in schools is unshielded twisted pair, which is most often used with star topologies.