Network monitoring - Big picture

Hi,

I'm looking for a software (free or not) that can analyse traffic on my network.

I don't want something like wireshark that gives me every packets.

I'm looking for something that can analyse traffic from a SPAN port and give me stats, charts, Top downloaders, Top tcp ports, stuff like that. (big picture of traffic on my network).

I don't want to use netflow on routers because we can't. I really want to use a SPAN port.

Something that can run 24/7 too.

Thank you !

nmap,
www.snort.org (IDS)
tripwire (IDS)
CERT (system scanner)
black ice (IDS)
Colasoft
InterMapper
LogicMonitor
The Microsoft Network Monitor
Munin
Nagios
Orion Network Performance Monitor
Splunk

thanks for the anwser but I was looking for apps like ntop

I found PRTG...which is a pretty cool product.

I have a nice overview of all traffic on my networks with VERY easy remote probe deployement.