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This is the troubleshooting story about me finding out why some
packets were getting dropped when running AX.25 over D-Star DV between
a Kenwood TH-D74 and an Icom 9700.
Troubleshooting: “Trouble”, from the latin “turbidus” meaning “a
disturbance”. “Shooting”, from American English meaning “to solve a
problem”.
The end result is this
post, and this is the
troubleshooting story.
The setup: laptop->bluetooth->D74->rf->9700->usb->raspberry pi.
I’m downloading from the raspberry pi, with the laptop sending back
ACKs. But one of the ACKs is not getting through.
axlisten -a
clearly showed that the dropped packet was being sent
from the laptop:
radio: fm M0XXX to 2E0XXX-9 ctl RR6-
But nothing received on the receiver side. I saw the D74 light up red
to TX, and the 9700 light up green on RX, but then nothing. Error
counters in ifconfig ax0
were counting up on the receiver side. So
something is being sent over the air.
And it wasn’t the first packet. All the ones before it were fine. They
were always fine. This packet was always dropped. It was always only
that packet that caused it to stall. The window size was set to 2, so
session establishment, RR0
, RR2
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