In some cases, your hosting provider may be charging you for bandwidth. In that event, you may want to be able to build your own daily, weekly and monthly reports on total throughput from your server(s).
There are several methods for doing this, however, some open source apps happen to be ready-made for just this and can be housed directly on your web server if you prefer.
These apps can measure not only traffic on multiple ports (i.e not only port 80, but toal throughput could include port 21 – FTP, 22 – SSH, 23 – Telnet, 25/110 – SMTP and POP as well as any custom ports for web applications you manage) but can also provide monitoring of disk space, cpu and memory utilization and more for your own systems management. Finally, these applications enable you to perform the simple math to verify total bandwidth based on your ethernet card(s) traffic. NOTE: Neither of these applications has been certified as usable for billing purposes, however, I believe they can be used to analyze the bandwidth reports provided by your ISP for hosting billing.
MRTG, which stands for Multi Router Traffic Grapher, and Cricket, easily manage the data acquisition and graphing necessary to give you easy-to-use visual reports on your system(s). MRTG is pre-installed some Linux distributions or can be downloaded from http://www.mrtg.org. Cricket can be found at http://cricket.sourceforge.net/.
MRTG, for example on Red Hat distributions, is found installed and accessible from /var/www/html/mrtg with its configuration files found at /etc/mrtg. MRTG has a very well supported community with extensive sites to review for tips, tricks and techniques, found here at http://people.ee.ethz.ch/~oetiker/webtools/mrtg/links.html.
I have actively used Cricket for monitoring data center infrastructure including hubs, routers and switches as well as *Nix and Windows servers. There is an active community with many ready-made configuration files for your devices. See here for examples and templates –> http://cricket.sourceforge.net/contrib/.
If there is a strong interest in this, I would look forward to writing a feature article on using Cricket to monitor the health of your web servers and devices.