From: http://sourceware.org/systemtap/wiki/WSNetTop

# stap nettop.stp
  PID   UID DEV     XMIT_PK RECV_PK XMIT_KB RECV_KB COMMAND
    0     0 eth0         66     344      18      19 swapper
 2469     0 eth0        214      39     167       1 Xvnc
23470     0 eth0         24      35       5       1 firefox-bin
 2281     0 eth0          1       1       0       0 wcstatusd
22446     0 eth0          1       0       1       0 sshd
 2538     0 eth0          0       1       0       0 metacity
23557     0 eth0          0       1       0       0 sh
23559     0 eth0          0       1       0       0 lspci
23566     0 eth0          0       1       0       0 sh

  PID   UID DEV     XMIT_PK RECV_PK XMIT_KB RECV_KB COMMAND
    0     0 eth0         14      80       0       3 swapper
 2469     0 eth0         32       2      20       0 Xvnc
22446     0 eth0          1       0       0       0 sshd
 2052    38 eth0          1       0       0       0 ntpd