Visitors to VTC.com will be able to view all introductory videos for each training course.
Free Trial Members will gain access to first three chapters for each training course.
Full Access Members have full access to VTC.com�s entire library of video tutorials.
Logical topologies define how all data moves on the network. So the way our network acts and the way our network looks may not be the same. The first logical topology that we will discus is the logical bus topology. Logical bus is very similar to physical bus in it. When computers communicate each time they send their data they will provide all of the other computers gets to see that data. The computers also have to compete for network access. So this computer is sending information through the hub all these are the computers who have to wait their turn until other computers finish communicating. Now depending on our central connecting device a network might act a little bit different. We would change this hub into a switch we wouldn't have to compete for network access anymore. Each computer would be on what is called their own conjunction domain. And conjunction just means; we all have to compete for network access. So Depending greatly on your network connecting device your computers are going to communicate better. As far as the benefits and the draw backs logical bus is great because it is easy to setup and easily used. A major draw back is still staying with the physical star we have that central point of failure with the central connecting device. The logical bus topology when used in conjunction with the physical star is called Ethernet. An Ethernet is the most common network seen today. With a logical ring topology computers communicate much in the same way they would in a physical ring. Our computers will send their traffic through the central connecting device and it will loop to each computer in the logical ring. Now we have our chorological ring setup with a physical star .This is correctly the most common implementation of our ring networks. The central connecting device is a light different from what we might see in a logical bus environment. Its called the multi station access unit .It has a special features built in. For example if this computer fails under a physical ring topology our entire network would go down. But because we move to a physical star a multi station access unit will close this port off and allow the ring to continue the flow in the correct manner. And these computers will put their data on what is called a token. As far this type of network is commonly referred to as token ring. So our computers will apply their data to the token and pass the token around .Some of the benefits of our logical ring topology when put in combination with a physical star and depending on the media used for the cabling between the computers and the multi station access unit we can get some very high speeded data transfer with very very reliable networks. But because it is physical store it can face with the problem of the center connecting device failing. In our next logical topology called the logical star we have several computers that will send their data signals through a transceiver. This is also called a multiplexer. A common example of what you would see as a multiplexer might be a cable modem. So we are going to take all our data signals from these computers and we are going to convert that data signal into a single data signal that will pass over the network. Now this can be very beneficial because you can choose which computer will gain access to the network at what time. So depending on our priorities assigned to our computers, computer one might get accessed to the network even though computer two was trying to access it before. This is called a deterministic based media access method because, the transceiver or the multiplexer with the terminal who gets network accessed .This can be greatly beneficial because one computer might control a very important process and implant and we will want that computer to get its network traffic quicker than let's say the receptionist at the front desk. Again because we are using logical star on physical star we still face with the problem of the central connecting device failing and causing the rest of the network to go down. But our transceiver is intelligent enough, if a single computer fails it will just close off that computers port and rest of the computers will be unaffected. This should give you an idea of how logical topologies in a great with physical topologies. Almost all of your networks implies today will fall under one of these logical and physical topologies. Next we discuss network categories.
Course: | CompTIA Network+ Certification (2005 Objectives) |
Author: | Brad Causey |
SKU: | 33608 |
ISBN: | 1-932808-53-1 |
Release Date: | 2005-03-22 |
Duration: | 7 hrs / 97 lessons |
Captions: | No |
Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |