If the server farm is running production levels of traffic today you can get statistics off a variety of networking devices passing the existing traffic. Switches, routers and firewalls all count every byte of traffic they pass. There are plenty of tools that can gather this traffic into tables via SNMP too, such as MRTG.
Do not average your traffic over too great a time peroid, you will miss busy hour peaks. At most, use 5 min averages.
- Bob
