Tunnel.py keep USRP transmitting UDP packets

Deal all,

When I run tunnel.py under the following path:
gnuradio/gr-digital/examples/ofdm, the USRP N210 keep sending UDP
packets
to the computer through network interface card. It costs too much
bandwidth
(2MB/s) of the Ethernet controller. Attached is the captured packets on
wireshark.

Is there anyone can help me with this problem?

Thanks,
Sihua