Concept of Different type Topology


1. Star topology: A star configuration is simple: Each of several devices has its own cable that connects to a central hub, or sometimes a switch, multipoint repeater, or even a Multistation Access Unit (MAU). Data passes through the hub to reach other devices on the network. Ethernet over unshielded twisted pair (UTP), whether it is 10BaseT, 100BaseT, or Gigabit, all use a star topology.

Star networks are one of the most common computer network topologies. In its simplest form, a star network consists of one central switch, hub or computer which acts as a router to transmit messages. If the central node is passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed by the two-way transmission time (i.e. to and from the central node) plus any delay generated in the central node. An active star network has an active central node that usually has the means to prevent echo-related problems.


Figure 1: Star topology

2. Ring topology: In a ring topology network computers are connected by a single loop of cable, the data signals travel around the loop in one direction, passing through each computer. Ring topology is an active topology because each computer repeats (boosts) the signal before passing it on to the next computer. One method of transmitting data around a ring is called token passing. The token is passed from computer to computer until it gets to a computer that has data to send.


Figure 2:- Ring topology

3. Bus topology:  In a bus topologies, all computers are connected to a single cable or “trunk or backbone”, by a transceiver either directly or by using a short drop cable. All ends of the cable must be terminated, that is plugged into a device such as a computer or terminator. Most bus topologies use coax cables.The number of computers on a bus network will affect network performance, since only one computer at a time can send data, the more computers you have on the network the more computers there will be waiting send data. A line break at any point along the trunk cable will result in total network failure. Computers on a bus only listen for data being sent they do not move data from one computer to the next, this is called passive topology.


    Figure 3:- Bus topology

4. Logical topology:  A logical topology describes how components communicate across the physical topology. The physical and logical topologies are independent of each other. For example, any variety of Ethernet uses a logical bus topology when components communicate, regardless of the physical layout of the cabling. This means that in Ethernet, you might be using 10BaseT with a physical star topology to connect components together; however, these components are using a logical bus topology to communicate.

Media Type Physical Topology Logical Topology
Ethernet Bus, star, or point-to-point Bus
FDDI Ring Ring
Token Ring Star Ring

Token Ring is another good example of a communication protocol that has a different physical topology from its logical one. Physically, Token Ring uses a star topology, similar to 10BaseT Ethernet. Logically, however, Token Ring components use a ring topology to communicate between devices. This can create confusion when you are trying to determine how components are connected together and how they communicate. FDDI, on the other hand, is straightforward. FDDI’s physical and logical topologies are the same: a ring.

5. Mesh topology:  A Mesh topology Provides each device with a point-to-point connection to every other device in the network. These are most commonly used in WAN’s, which connect networks over telecommunication links. Mesh topologies use routers to determine the best path. Mesh networks provide redundancy, in the event of a link failure, meshed networks enable data to be routed through any other site connected to the network. Because each device has a point-to-point connection to every other device, mesh topologies.mesh_topology

         Figure 4:-   Mesh topology

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