The Need for Speed: Early warning signs for congestion problems - Understanding LAN Switching

Now, how can you tell if you have congestion problems in your network? Well, some early things to look at, some early things to watch out for, include increased delay on our file transfers.If basic file transfers are taking a long, long time in the network, that means we may need more bandwidth. Also, another thing to watch out for is print jobs that take a very long time to print out.From the time we queue them from our workstation, till the time they actually get printed, if that's increasing, that's an indication that we may have some LAN congestion problems.Also, if your organization is looking to take advantage of multimedia applications, you're going to need to move beyond basic shared LAN technologies, because those shared LAN technologies don't have the multicast controls that we're going to need for multimedia applications.

Typical Causes of Network Congestion

Some causes of this congestion, if we're seeing those early warning signs some things we might want to look for, if we have too many users on a shared LAN segment. Remember that shared LAN segments have a fixed amount of bandwidth.As we add users, proportionally, we're degrading the amount of bandwidth per user. So we're going to get to a certain number of users and it's going to be too much congestion, too many collisions, too many simultaneous conversations trying to occur all at the same time.

And that's going to reduce our performance. Also, when we look at the newer technologies that we're using in our workstations. With early LAN technologies the workstations were relatively limited in terms of the amount of traffic they could dump on the network.Well, with newer, faster CPUs, faster busses, faster peripherals and so on, it's much easier for a single workstation to fill up a network segment.So by virtue of the fact that we have much faster PCs, we can also do more with the applications that are on there, we can more quickly fill up the available bandwidth that we have.

Network Traffic Impact from Centralization of Servers

Also, the way the traffic is distributed on our network can have an impact as well. A very common thing to do in many networks is to build what's known as a server farm for example.Well, in a server farm effectively what we're doing is centralizing all of the resources on our network that need to be accessed by all of the workstations in our network.So what happens here is we cause congestion on those centralized segments within the network. So, when we start doing that, what we're going to do is cause congestion on those centralized or backbone resources.

Servers are gradually moving into a central area (data center) versus being located throughout the company to:

 - Ensure company data integrity
 - Maintain the network and ensure operability
 - Maintain security
 - Perform configuration and administrative functions

More centralized servers increase the bandwidth demands on campus and workgroup backbones