How to monitor bandwith on a a single interface on RB411 ?

How to monitor bandwith on a a single interface on RB411

I have a RB411 used for distrubuting adsl (clients aut by usermanager pppoe)
I have one lan port used for internal adsl usage - how can i monitor the bandwith that is used by this single lan interface?

can one monitor and/or shape bandwith one of you lan interfaces/

Do you have any queues for PPPoE users?

I have pppoe setup running for all my klients. However i am not trying to setup a pppoe account.

My setup is as follow:

I have clients connecting via wlan interface and authentication via pppoe accouns. This all works fine.
I then use one of the lan ports to route adsl to my wireless clients.
The second lan port connects to my office network directly and i draw internet directly without authenticating with pppoe.

what i am trying to find out is can i monitor this lan port? Is there a way to monitor the usage without pppoe.

The other question i have which is directly related is as follow.
My internet service provider tells me i use 3 gig for example. Is there a way that i can astablish if 3 gig actually did come in trough that specific lan port which is connected to my adsl router?

Thanks