E1 line debug L1/L2

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Ivan Babanov ivan.babanov at gmail.com
Wed Oct 7 22:14:03 UTC 2020


Hello all,

Brief question. Is it possible to debug E1 line by connecting it to the 2nd
port of the same NIC making a wired loop? Is it enough to open->ioctl->read
from /dev/dahdi/channel to get a stream of LAPD SABME messages transmitted
by BSC?

A bit more details for those interested

I'm still trying to bring up BTS Nokia Flexi with OSMO-BSC.
I'm using an E1 card Digium TE405P on the server side.
OSMO-BSC is connected with Nokia BTS via a single E1 line.
Looks like on Level1 everything is ok because BTS can detect the link and
raise an alarm if the wire is getting disconnected.
I can observe some data from timeslots on BTS side and if some channel is
configured as D-Channel in /etc/dahdi/system I see transmission of block
"01111110".
But the problem is that LAPD link is not establishing. I can't find any
tries on BTS side and BSC does not receive anything from BTS, just set of
SABME messages in PCAP file.
T200 expires and so on. I tried various T200 values. So, now it looks for
me like L1 does not receive anything from L2 on BSC side and nothing is
transmitted over the wire to BTS.

dahdi_tool shows status "OK"

So, my nearest plan to check data transmission over wired loopback.

Thank you
Babanov Ivan
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