How to monitor bandwidth on host which uses bridge-util and virtualization

Question

I am running a debian squeeze box with bridge-util and LXC containers.

I guess this is a 2 part request.

1. I would like to know what my total bandwidth usage is
2. I would like to see it broken down by virtual host.

Hosts all have fixed IP addresses, no DHCP at all.

I came across ntop, MRTG, WireShark but can't figure out which to use, and they all seam so bulky.

What's the best tool to capture usage without interfering with the bridge? I like if it has minimal impact on the overall system, meaning not slowing things down too much, little memory usage etc.

I don't need graphs, just a daily, weekly, monthly total would do.