Re: [Discuss-gnuradio] USRP2 / Tunnel.py packet reflection issue

[Marcus D. Leech]

On 10/31/2011 06:01 PM, Tuan (Johnny) Ta wrote:

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

We used to have this problem "back in the day" with packet-radio, using analog FM transceivers--they were often notoriously sluggish
  in turning around the TX/RX logic.

You might try zero-stuffing the TX frames--that's basically what we did back in the day.  Although the XCVR2450 short turn around fairly
  quickly, it's not infinitely quick.

-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org