Case Study

SCENARIO

ESSENCE OF THE CASE

Following are the essential elements in this case:

• Timeout problems

• Times when no connectivity exists at all

• Loss of connectivity

• Use of hubs

You have been hired as a consultant to work for ABC, Inc., because the company is having specific problems with its network. The problems range from clients timing out, loss of connectivity when trying to access network resources, to no connectivity to the network during peak hours. The network consists of four core switches, eight closets to connect the user segments consisting of four 24-port hubs each, and two redundant core routers. You need to analyze the network, find the problems, and implement a solution.

ANALYSIS

As a consultant going to ABC, Inc., you immediately start to look at the network documentation and network topology maps. You need to make sure that there aren't any obvious errors in design (such as using stacked hubs in closets) and so on. It is your responsibility to check the network layout to see if there are any bottlenecks anywhere , choke points on the network, or mismatched bandwidth speeds going into critical areas. For example, you should make sure that you have a backbone segment with your critical servers that runs on Gigabit Ethernet and then move to the desktop users, most likely coming out of switch closets located around the building you may be working in. These connections should run at a minimum of 100Mbps.

In today's networks, most businesses send around very large files, both video and voice, so you can't get away with using hubs running at 10Mbps anymore. The nature of a hub is to broadcast data out of every port, whereas a switch keeps a MAC-to-port memory map to keep the number of broadcasts down to a minimum. Not using switches is a design flaw. Using hubs can cause massive collision counts, and if the collision counts are too high, your clients may experience time outs, disconnects, or just bad performance.

In any case, by running a protocol analyzer on your network, you can find any excessive broadcasts, collisions, or extra protocols that may be traversing the network. As a solution, you should run a protocol analyzer in the closet hubs, determine that traffic volume is way too high with collisions and broadcast traffic, and put in switches to control the traffic better. By doing so, you upgrade the network desktop users from 10Mbps to 100Mbps, a connection speed 10 times faster than they were using before. These changes solve all four network problems the company was experiencing.