[j-nsp] JUNOSe ethernet overhead accounting

[Roman A. Nozdrin]

Hello.

Recently we have purchased E120 to remove software-based PPPoe ACs from 
our network. During the migration BRAS challenged me.
1) There are several service definitions to count different traffic 
patterns apart. Customer's iface attached policy statistics and SM 
statistics are both enabled. BRAS sends RADIUS accounting packets for 
every activated service.  Everything is perfect so far. Recenlty I have 
noticed that SM service-session RADIUS accounting data(byte count to be 
exact) differs with real IP packet length. It differs for 30 byte per 
each IP packet. It looks clear for me, that JUNOSe SM counts all of 
interfaces column overhead(ethernet-802.1q-pppoe in my situation) 
instead of raw IP packet length. But BRAS accounts the overhead for SM 
service-sessions only. In the same time RADIUS accounting for the entire 
PPPoE session is correct and doesn't include 30 byte overhead. So here 
is the question, is there any knob to exclude overhead accounting in JUNOSe?
2) The second question is the way to check particular PPPoE session 
status. So far I decided to utilise RADIUS CoA requests. The marker is 
JUNOSe RADIUS client's reply. I hope someone has more elegant solution 
for the task.

I will appreciate any suggestion.

WBR
Roman A. Nozdrin