Network Performance: Problem Basics
The term network performance refers to how efficiently the network responds to users’ needs. It goes without saying that any access to resources that involves a network will be slower than similar access that doesn’t involve a network.
For example, it takes longer to open a Word document that resides on a network file server than it takes to open a similar document that resides on a user’s local hard drive. However, it shouldn’t take much longer. If it does, you have a network performance problem.
Network performance problems are among the most difficult network problems to track down and solve. If a user simply can’t access the network, it usually doesn’t take long to figure out why: A cable is broken, a network card or hub is malfunctioning, a user doesn’t have permission to access the resource, and so on. After a little investigation, the problem usually reveals itself. You fix it and move on to the next problem.
Unfortunately, performance problems are messier. Here are just a few of the reasons that network administrators hate performance problems:
Performance problems are difficult to quantify. Exactly how much slower is the network now than it was a week ago, a month ago, or even a year ago? Sometimes the network just feels slow, but you can’t quite define exactly how slow it really is.
Performance problems usually develop gradually. Sometimes, a network slows down suddenly and drastically. More often, though, the network gradually gets slower, a little bit at a time, until one day when the users notice that the network is slooow.
Performance problems often go unreported. Users gripe about the problem to each other around the water cooler, but they don’t formally contact you to let you know that their network seems 10 percent slower than usual. As long as they can still access the network, they just assume that the problem is temporary or just in their imaginations.
Many performance problems are intermittent. Sometimes, a user calls you and complains that a certain network operation has become slower than molasses — and by the time you get to the user’s desk, the operation performs like a snap.
Sometimes, you can find a pattern to the intermittent behavior, such as it’s slower in the morning than in the afternoon, or it’s only slow while backups are running or while the printer is working. Other times, you can’t find a pattern.
Performance tuning is not an exact science. Improving performance sometimes involves educated guesswork. Will upgrading all the users from 100 Mbps to gigabit Ethernet improve performance? Probably. Will segmenting the network improve performance? Maybe. Will adding another 4GB of RAM to the server improve performance? Hopefully.
The solution to performance problems is sometimes a hard sell. If a user can’t access the network because of a malfunctioning component, there’s usually not much question that the purchase of a replacement is justified. However, if the network is slow and you think you can fix it by upgrading the entire network to gigabit Ethernet, you may have trouble selling management on the upgrade.