Getting Your Internet Resources Under Control
Remember that not all T1s are equal. Even though virtually all ISPs have T1 or T3 connections to the Internet backbone, the particular configuration of the selected ISP will affect your site's performance. The fewer routers between the ISP and the backbone, the better. An ISP with T3 connections that are five routers away from the backbone easily could be slower than an ISP with T1 connections only two routers away. The number of routers (or "hops") between you and other sites will also affect communication speed. If possible, before selecting an ISP, have it trace the route between its site and other sites.
Excess Bandwidth
Once your Internet connection is in place, you
should analyze how much available bandwidth you are using and how it is being utilized. You may be paying for more bandwidth than you need, or you may not have enough. Consider what kind of traffic is generating the bandwidth (e-mail, Web surfing or FTP downloads, for instance) and when your peaks occur. Some of these questions can be answered with tools built into many routers. Most will require special software.
Most types of router software have integrated commands--such as Cisco Systems' IOS command "show int s0"--that can provide a record of recent traffic at the site. Your router may tell you how many bytes and packets it recently sent and received, let you clear timers and counters, and tell you how long it's been since you reset them. Router commands tend to be short-term. They act as a snapshot of what has happened since the counters were cleared.
Router commands, though primitive, can provide useful information. If, however, you really want to get a handle on your Internet traffic, you'll ne
ed some type of network-management utility--such as IBM Corp.'s NetView or Dartmouth's Intermapper--combined with a firewall and a router. Firewalls usually have more sophisticated commands that use Unix syslogd for logging, and they are typically configu
red to intercept traffic data. We use Intermapper mapping software, which records such usage patterns as peaks and outages. Among the most useful features is the ability to sort out which applications are consuming bandwidth for a given system. Most routers can break down traffic by protocol, such as TCP/IP, IPX or AppleTalk. However, they can't distinguish where data is coming from or going to and how many bytes are occupied with FTP downloads, as Intermapper and similar products do.
With such network-management utilities installed on your firewall, you can determine the excessive usage culprits on your network, which are most likely Web browsing and FTP access. These are followed by an up-and-coming bandwidth bandit--PointCast Network. Far less likely
are telnet and e-mail. Although e-mail is the most active application on the Internet, it isn't a bandwidth gobbler for most systems.
It is also possible for users outside of your site to drain bandwidth from your system. One of our large corporate customers placed a picture of Santa Claus on its site during the 1996 holiday season. As word of the picture spread quickly throughout the Internet community, the site--which uses a T1 connection--became so hopelessly overloaded by downloads, its firewall crashed repeatedly. The only solution was to remove the picture. It is also possible for saboteurs to send a steady stream of large packets to a site, crowding out legitimate traffic.
Besides understanding your usage patterns, you should make sure your hardware is up to the task. Using an antiquated router or one with insufficient RAM will guarantee performance problems. The quality of the line your telco provides is also a critical factor. Use your router to check for errors--such as interface resets--on
the line.
In our experience, line errors usually indicate a problem with the telco's equipment. One of our largest corporate customers had a T1 connection that charitably could have been called "flaky." Small-packet pings would travel unscathed, but large-
packet pings failed. Because the telco support staffs usually suggest replacing and rebooting your equipment before checking their end, we swapped or restarted every possible piece of equipment before calling. As we suspected, the problem was at the telephone company's end.
Your ISP Can Help
Once you understand your usage patterns and you know that your equipment is working correctly, you can start optimizing your Internet resources. By isolating bandwidth-consuming operations, you can free your primary server to run at top speed. Newsgroups can monopolize a remarkable amount of bandwidth. Not only are they popular and easy to access, they are often bloated by attached images.
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