I have been running into problems using tunnel.py as well so instead of creating a new post I thought I'll just continue this thread.
My setting: USRP2 XCVR2450 Ubuntu 10.04 (32bit) The problem I have is that after running tunnel, whenever I do ping, my system gets stuck on the ARP exchange. Say A wants to ping B. A broadcasts an ARP packet to find the MAC address of B's IP. B gets the ARP request, immediately sends an ARP response back to A with its MAC. However, in my system, A never gets the ARP reply. I seriously can't think of a reason for this. I can guess a possible cause is that B sends the ARP reply too quickly that A doesn't have enough time to go from transmit mode to receive mode (XCVR2450 is a half-duplex daughterboard). But I don't know how to verify this hypothesis. Can anyone help me? Thank you, Johnny On Thu, Oct 20, 2011 at 11:24 AM, Marcus D. Leech <mle...@ripnet.com> wrote: > On 20/10/2011 10:25 AM, David Barton wrote: > > > I have been troubleshooting an issue with possible packet relflections and > cannot figure out the cause. I am running tunnel.py on two USRP2s that are > cabled together with a 20dB attenuator between them. The settings I am > using on both sides for tunnel.py are: > > Tx Gain: 15 dB > Rx Gain: 10 dB > Carrier Threshold: -80 > Rx Tunnel Freq: 400 MHz > Modulation: GMSK > Bit Rate: 1Mb/sec > > When I use VLC to stream a video from computer A to computer B over the > USRP link it works ok but there are alot of reflected packs being recorded > by computer A. The same thing happens when I try to stream from computer A > to computer B. This also occurs when I use iperf to test the link. > Strangely, though there are NO reflected packets when I ping between the > computers. > > Below is a paste of some of the output from computer A. I put in a > timestamp on the left of when events occur. I also put in an explicit > statement to print out when tunnel is backing off and for how long. I added > sequence number to make it blatantly obvious that the computer is receiving > its own packet. Any packet with a sequence number beginning originates from > computer A. If the packet originated from computer B it shows up at > RX_packet=none. As it shows computer A is receiving its own packets! > [ 63.61 ] Tx: seq_no = 100054 | len(payload) = 1448 > [ 63.61 ] Tx: seq_no = 100055 | len(payload) = 186 > [ 63.61 ] Tx: seq_no = 100056 | len(payload) = 1310 > [ 63.61 ] Tx: seq_no = 100057 | len(payload) = 1448 > [ 63.61 ] Tx: seq_no = 100058 | len(payload) = 1021 > [ 63.61 ] Backing off for 0.001 sec > [ 63.62 ] Backing off for 0.002 sec > [ 63.62 ] Backing off for 0.004 sec > [ 63.63 ] Backing off for 0.008 sec > [ 63.64 ] Backing off for 0.016 sec > [ 63.64 ] Rx: ok = True | seq_no = 100054 | len(payload) = 1448 > [ 63.66 ] Backing off for 0.032 sec > [ 63.64 ] Rx: ok = True | seq_no = 100055 | len(payload) = 186 > [ 63.66 ] Rx: ok = True | seq_no = 100056 | len(payload) = 1310 > [ 63.66 ] Rx: ok = True | seq_no = 100057 | len(payload) = 1448 > [ 63.67 ] Backing off for 0.064 sec > [ 63.67 ] Rx: ok = True | seq_no = 100058 | len(payload) = 1021 > [ 63.72 ] Tx: seq_no = 100059 | len(payload) = 1448 > [ 63.72 ] Tx: seq_no = 100060 | len(payload) = 70 > [ 63.72 ] Tx: seq_no = 100061 | len(payload) = 1448 > [ 63.72 ] Tx: seq_no = 100062 | len(payload) = 150 > [ 63.72 ] Tx: seq_no = 100063 | len(payload) = 1448 > [ 63.72 ] Tx: seq_no = 100064 | len(payload) = 248 > [ 63.72 ] Backing off for 0.001 sec > [ 63.72 ] Backing off for 0.002 sec > [ 63.73 ] Backing off for 0.004 sec > [ 63.74 ] Backing off for 0.008 sec > [ 63.75 ] Backing off for 0.016 sec > [ 63.74 ] Rx: ok = True | seq_no = 100060 | len(payload) = 70 > [ 63.75 ] Rx: ok = True | seq_no = 100061 | len(payload) = 1448 > [ 63.76 ] Backing off for 0.032 sec > [ 63.75 ] Rx: ok = True | seq_no = 100062 | len(payload) = 150 > [ 63.76 ] Rx: ok = True | seq_no = 100063 | len(payload) = 1448 > [ 63.76 ] Rx: ok = True | seq_no = 100064 | len(payload) = 248 > [ 63.78 ] Tx: seq_no = 100065 | len(payload) = 1448 > [ 63.78 ] Tx: seq_no = 100066 | len(payload) = 566 > [ 63.78 ] Tx: seq_no = 100067 | len(payload) = 1448 > [ 63.78 ] Tx: seq_no = 100068 | len(payload) = 987 > [ 63.78 ] Backing off for 0.001 sec > [ 63.79 ] Backing off for 0.002 sec > [ 63.79 ] Backing off for 0.004 sec > [ 63.79 ] Backing off for 0.008 sec > [ 63.8 ] Backing off for 0.016 sec > [ 63.8 ] Rx: ok = True | seq_no = 100066 | len(payload) = 566 > [ 63.82 ] Backing off for 0.032 sec > [ 63.82 ] Rx: ok = True | seq_no = 100067 | len(payload) = 1448 > [ 63.82 ] Rx: ok = True | seq_no = 100068 | len(payload) = 987 > [ 63.84 ] Tx: seq_no = 100069 | len(payload) = 1448 > [ 63.84 ] Tx: seq_no = 100070 | len(payload) = 1448 > [ 63.84 ] Tx: seq_no = 100071 | len(payload) = 1448 > [ 63.84 ] Tx: seq_no = 100072 | len(payload) = 321 > [ 63.84 ] Tx: seq_no = 100073 | len(payload) = 1448 > [ 63.84 ] Tx: seq_no = 100074 | len(payload) = 855 > [ 63.84 ] Backing off for 0.001 sec > [ 63.84 ] Backing off for 0.002 sec > [ 63.85 ] Backing off for 0.004 sec > [ 63.85 ] Backing off for 0.008 sec > [ 63.86 ] Backing off for 0.016 sec > [ 63.87 ] Backing off for 0.032 sec > [ 63.86 ] Rx: ok = True | seq_no = 100070 | len(payload) = 1448 > [ 63.89 ] Rx: ok = True | seq_no = 100071 | len(payload) = 1448 > [ 63.89 ] Rx: ok = True | seq_no = 100072 | len(payload) = 321 > [ 63.89 ] Rx: ok = True | seq_no = 100073 | len(payload) = 1448 > [ 63.9 ] Backing off for 0.064 sec > [ 63.9 ] Rx: ok = True | seq_no = 100074 | len(payload) = 855 > > Does anyone have any idea why this could be occurring? I thought maybe it > would be a physical reflection but dont understand why ping packets would > not be reflected in that case. > > Thanks, > Dave > > There's generally only about 45dB of isolation available between TX and > RX, so if you're running in full-duplex, your receiver will see its > own transmissions. > > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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