Background
With just over 100 PCs this is not a big network, but the reliability of the services was never quite as it should have been. Every week users would complain of their PCs just hanging for no particular reason, and eventually Full Control Networks were called in to investigate the network.
Approach
The first action carried out was to audit the current network to understand how it was connected together and configured. This work showed the first issue with the network design was the way the network had grown over the last few years.
The network started out as a couple of switches connected together but had become a stack of seven switches connected together. All these switches were edge switches, that although do work in this configuration, they are not tuned to the switching characteristics needed at the centre of a network.
The audit also showed that the Servers were connected to the network on 1000Mbs links, but the sever switches connected to the rest of the network using a 100Mbs connection. Therefore the perception of Gigabit attached servers was not a useful one in terms of realistic performance.
The configuration of the network was also audited, and apart from a few unwanted protocols being broadcast, there was nothing that could explain the issues being experienced by the users.
At the start of this project, the customer felt that there must be a bottleneck in the network somewhere, so the traffic profiles through the switches was monitored. This showed that there were occasional peaks of traffic around 30% to some of the servers, but generally traffic levels were less than 2%.
The customer also asked that the traffic generated by some of the busy users be monitored. The test was set up between one user and the network and the “heavy duty” work load was monitored. The tests showed that the PC in question could only put 16Mbs of traffic onto the network (NIC card bus limitations) and hence was not capable of overloading the connection.
Recommendations
The review showed the customer that there was not an issue with the amount of traffic in the network, but there was a problem with how the network had grown and developed.
The use of more and more edge switches had not broken any design rules, but had created a network that just was not very good at the job it was being asked to do. Working with the customer it was found that there were a number of new projects planned over the next few years that gave the opportunity to put forward a business case to replace the network with a solution designed to cope with these requirements.
Full Control Networks were retained to produce the specification document for this work and help select the appropriate partner.
Conclusions
This work was started on the basis that there must be a bottleneck in the network somewhere causing these issues. The work carried out by Full Control Networks not only showed this not to be the case, but also showed that some of the heavy usage PCs were not capable of putting enough traffic on the network for this ever to be an issue.
The understanding of how a network operates enabled us to look at the basic design and question its ability to cope in the current situation. Any new network would not be purchased from us hence an objective look at this situation could be made.
The user was left in a situation were they understood the issues, a business case was presented for the necessary upgrades and a specification document produced to help them move forward in the right direction.
Last Updated: 21/01/2007