[Discuss-gnuradio] tunnel.py sends packages of incorrect size

[Weixian Zhou]

I am doing test with tunnel.py and following the readme instructions located gnuradio/gr-digital/examples/narrowband.

on machine A:

sudo ./tunnel.py --tx-freq=2.51G  --rx-freq=2.515G -c 50 -r 0.5M

then

sudo ifconfig gr0 192.168.200.1

on machine B:

sudo ./tunnel.py --tx-freq=2.515G  --rx-freq=2.51G -c 50 -r 0.5M

then

sudo ifconfig gr0 192.168.200.2

Then I can see packages tx/rx on both machines:

URx: ok = True len(payload) =   54

Rx: ok = True  len(payload) =   90

Rx: ok = True  len(payload) =  353

Tx: len(payload) =   90

Tx: len(payload) =   54

...

After I ping from A to B, I found A only sends packages of fixed size 42:

UTx: len(payload) =   42

UTx: len(payload) =   42

UTx: len(payload) =   42

UTx: len(payload) =   42

...

But the default package size of ping is 56 from the man page. Where did the packages of size 42 come from? Anyone has idea?

I am using two USRP N210s, the daughter boards are both XCVR2450.

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Regards,

Weixian Zhou