Antivirus software, spam filters and firewalls all help prevent the generation of junk traffic within your network, so make sure they are enabled and kept up-to-date. Modesto says it is worth considering outsourced antispam and antivirus services, as they typically use multiple products to provide ongoing protection on the occasions when a vendor takes an extra day to provide an update for the latest virus or worm.
Atkinson also suggests blocking e-mail attachments to the extent that is feasible, and configuring software so that large attachments are held on the server as long as possible. Just because 10 people are sent copies of a multi-megabyte PowerPoint deck, that doesn't mean they are all going to open it. User education comes into this too, as it would probably have been better to store the file in a shared folder, and send a link to those 10 people. Atkinson also recommends disabling the "All" group in e-mail -- it typically comes at the top of the list, so users will accidentally select it from time to time. It's also a sitting target for mail viruses and worms.
"Make patch management... and laptop security a priority," advises Modesto, though updates should be performed at night or staggered throughout the day to avoid congestion. He also warns that some popular printers run cut-down versions of old operating systems and can be affected by worms. Monitoring tools such as MRTG can reveal unexpected traffic: "a little bit of graphing goes a long way."
Users may want to install legitimate but unapproved software that adds to the load, such as utilities that load fresh wallpaper every day. A noticeable spike can occur if enough people follow suit. Or the program might hog RAM or another resource, causing poor overall performance. "It's really about knowing what's running, who's running it, and what they're doing," said Prichard.
Broadcast traffic that's not relevant to all users can also be regarded as junk. Jae-Won Lee, product marketing manager for data networking solutions at Nortel Asia Pacific, says this can be reduced by dividing the network into multiple virtual LANs (VLANs). Segregating a 100 user LAN into five VLANs will hide around 80 percent of broadcast traffic.
"For example, if an organisation has multimedia, CAD/CAM design or on-line collaboration tools that use multi-cast protocols which inherently produce a lot of broadcast traffic then these functional groups can be separated from the rest of the organisation as not to impact other traffic on the network," he says.
Although it's important to monitor the network, Atkinson warns that it is possible to overdo things by sending too many pings and test frames. Some of his customers were losing one third of their bandwidth to multiple and inappropriately configured network management tools until he set them straight.
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