For a Ubuntu Samba file server running Apache and an ftp client what amount of network traffic would be normal when no users are connected? 

I am strictly a Windows admin and have just installed Ubuntu Server for the first time. I am using it as a file server/ftp server (for the IT Dept only) and I am hosting a website (which is also available to the IT Dept only).

I have noticed what appears to be traffic when the machine should be not in use. I have installed and am running VNSTAT, which shows about 82kb rx and 84kb tx in about an hour. This may or not be accurate. It looks like there is more traffic on the switch for that port.

I am looking for advice on monitoring and understanding network traffic for Ububtu Server.

Understanding network traffic, while part of my daily job, is probably my weakest area. I try to learn something new everyday/week and it seems there is alot out there on this subject, but nothing specifically written for a newby to see satisfying results immediately.

I guess my questions are- 1) how much traffic is normal for the situation listed above and 2) whats a good starting point (that I can build on) for understanding traffic