Network+Topologies

Network Topologies  Back A physical topology defines the way in which computers, printers, and other devices are connected to a network. A logical topology describes how the hosts access the medium and communicate on the network. The type of topology determines the capabilities of the network, such as ease of setup, speed, and cable lengths.

Physical Topologies The common LAN physical topologies:

Bus Topology

In the bus topology, each computer connects to a common cable. The cable connects one computer to the next, like a bus line going through a city. The cable has a small cap installed at the end, called a terminator. The terminator prevents signals from bouncing back and causing network errors.



Ring Topology

In a ring topology, hosts are connected in a physical ring or circle. Because the ring topology has no beginning or end, the cable does not need to be terminated. A specially-formatted frame, called a token, travels around the ring, stopping at each host. If a host wants to transmit data, the host adds the data and the destination address to the frame. The frame then continues around the ring until the frame stops at the host with the destination address. The destination host takes the data out of the frame. 



Star Topology

The star topology has a central connection point, which is normally a device such as a hub, switch, or router. Each host on a network has a cable segment that attaches the host directly to the central connection point. The advantage of a star topology is that it is easy to troubleshoot. Each host is connected to the central device with its own wire. If there is a problem with that cable, only that host is affected. The rest of the network remains operational.



Hierarchical or Extended Star Topology

A hierarchical or extended star topology is a star network with an additional networking device connected to the main networking device. Typically, a network cable connects to one hub, and then several other hubs connect to the first hub. Larger networks, such as those of corporations or universities, use the hierarchical star topology. 



Mesh Topology

The mesh topology connects all devices to each other. When every device is connected to every other device, a failure of any cable does not affect the network. The mesh topology is used in WANs that interconnect LANs.



<span style="font-family: 'Comic Sans MS',cursive; font-size: 12pt; line-height: normal; margin: 0in 0in 10pt;">Logical Topologies

<span style="font-family: Georgia,serif; font-size: 120%; line-height: normal; margin: 0in 0in 10pt;">The two most common types of logical topologies are broadcast and token passing. <span style="font-family: Georgia,serif; font-size: 120%;">In a broadcast topology, each host addresses either data to a particular host or to all hosts connected on a network. There is no order that the hosts must follow to use the network – it is first come, first served for transmitting data on the network. <span style="font-family: Georgia,serif; font-size: 120%;">Token passing controls network access by passing an electronic token sequentially to each host. When a host receives the token, it can send data on the network. If the host has no data to send, it passes the token to the next host, and the process repeats itself.

<span style="font-family: 'Comic Sans MS',cursive; font-size: 14pt; line-height: normal; margin: 0in 0in 10pt;">Summary

<span style="font-family: Georgia,serif; font-size: 120%;">Topologies are designing to describe the way of building a network. There are two types of LAN topologies: physical and logical topology. Physical topology shows how devices are connected with cables and network components, while logical topology shows how devices are connected to the user. Here are types of physical topology: <span style="font-family: Georgia,serif; font-size: 120%;">· Bus <span style="font-family: Georgia,serif; font-size: 120%;">Each computer connects to one common cable, one computer next to other. At the end of the cable, there is a terminator which prevents signal from bouncing back.

<span style="font-family: Georgia,serif; font-size: 120%;">· Ring <span style="font-family: Georgia,serif; font-size: 120%;">Computers are connected in physical ring or circle in their topology. The signals recreated by each computer because there is no end or start for the topology. If a computer wants to transmit data, the host adds the data and the destination address to the frame. Then, the frame continues all around the ring.

<span style="font-family: Georgia,serif; font-size: 120%;">· Star topology <span style="font-family: Georgia,serif; font-size: 120%;">In this topology, it is needed to have a control connection point such as a hub or switch. Each device attach directly to the central connection point by cable segment. One of its advantages is that it is easy to troubleshoot. That means if there is a problem in one cable, the other computers will be not affected.

<span style="font-family: Georgia,serif; font-size: 120%;">· Hierarchical or Extended Star topology <span style="font-family: Georgia,serif; font-size: 120%;">It is a star topology with an additional networking device connected to the main networking device. It means that one network cable connects to one hub, and many hubs will connect the first hub.

<span style="font-family: Georgia,serif; font-size: 120%;">· Mesh topology <span style="font-family: Georgia,serif; font-size: 120%;">All devices are connected to each other in the mesh topology. Every device is connected to every other device. Therefore, any problem will happen in any cable, the network will not be affected.

<span style="font-family: Georgia,serif; font-size: 120%;">Logical topology has two types which are broadcast and token passing. <span style="font-family: Georgia,serif; font-size: 120%;">· Broadcast <span style="font-family: Georgia,serif; font-size: 120%;">It means a host may send data to a particular device or to all devices that are connected to the network.

<span style="font-family: Georgia,serif; font-size: 120%;">· Token passing <span style="font-family: Georgia,serif; font-size: 120%;">It controls network access by passing sequentially an electronic token to each host. Therefore, if a host receives a token, it can send it on the network. However, if the host has no data, it passes the token to the next host.

<span style="font-family: 'Comic Sans MS',cursive; font-size: 12pt;">Resource

<span style="font-family: Georgia,serif; font-size: 120%;">CISCO Networking Academy Program <span style="font-family: Georgia,serif; font-size: 120%;">