Re: [Discuss-gnuradio] Running tunnel.py/benchmark tx.py (OFDM) with XCVR2450?

[Florian Schlembach]

> > We are now trying to establish an TCP/IP connection between both USRP2s
> > with the tunnel.py script.
> > Unfortunately, it says "Destination Host unreachable" when pinging the
> > other USRP. We should have set up the tunnel correct as some packets are
> > received and transmitted after having configured the IP address. The
> > pinged USRPs is indicating the received icmp packet but there is still
> > no confirmed ping-request though.
>
> Short answer; dont do that. Yes, this particular USRP is a network
> device, but that is completely unrelated to the purpose of tunnel.py.
> You probably have to play with routing tables to make this work...

Why is that unrelated to the purpose of tunnel.py? Shouldnt a simple 
ping request be a basic application of using this TUN/TAP application?
Anyway, we have now set up the routing table correctly by using TUN 
instead of TAP.
As we are transmitting the ping from one of the USRPs, we are also 
receiving them at the RX-USRP which is answering with a ping reply:

RX-USRP:

-
TIMEOUT
Rx: ok = True  len(payload) =   84
Tx: len(payload) =   84
send now!
UTIMEOUT
-

Observing the IP dataflow via Wireshark (at RX-USRP) confirms that.
However, we are NOT receiving this ping reply and the transmitting USRP.
It seems, like it cannot transmit and receive simultaneously. Exactky 
the same happens if we swap the role of transmitting and receiving USRPs.

Anybody has an idea how we could overcome this problem? Basically, we 
want to measure the latency of a "real" application.