PageOutline = layer23 =

The ''layer23'' program is the playground we use for developing the GSM Protocol layers 2 and 3 (GSM TS 04.05, 04.06, 04.08)

Using the layer23 program, you can: * Connect to /tmp/osmocom_l2 socket created by [wiki:osmocon] to exchange data from [wiki:L1A_L23_Interface]. * Receive GSM Layer1 frames. * Dump received GSM Layer1 frames and print some analysis. * Send the Layer1 frames as GSMTAP packets to wireshark (see [wiki:WiresharkIntegration])

The ''layer23'' program is used in combination with the [wiki:layer1.bin] firmware.

=== Usage === {{{
./layer23 -a 871 -i 127.0.0.1
}}}

This will connect to the [wiki:osmocon] application and will receive GSM Layer1 frames. The receiving is done in the src/main.c and the frames will be passed to src/l1ctl.c,
from there into src/lapdm.c and finally into src/layer3.c

The output of the layer23 application is currently looking like this: {{{
Found CCCH burst(s): TDMA: (0003/08/39) tc:3 49 06 1b 3b 80 62 f2 20 01 3a c8 07 0a 15 65 04 b9 00 00 80 00 02 1b si: 0x1b
SI3 on wrong TC
Found sync burst: SNR: 16384 TDMA: (0003/15/46) bsic: 49
Found sync burst: SNR: 16384 TDMA: (0003/25/05) bsic: 49
Found sync burst: SNR: 16384 TDMA: (0003/09/15) bsic: 49
Found sync burst: SNR: 16384 TDMA: (0003/19/25) bsic: 49
Found CCCH burst(s): TDMA: (0003/07/39) tc:4 31 06 1c 62 f2 20 01 3a 65 04 b9 00 00 80 00 53 2b 2b 2b 2b 2b 2b 2b si: 0x1c
SI4 on wrong TC
Found sync burst: SNR: 16384 TDMA: (0003/14/46) bsic: 49
Found sync burst: SNR: 16384 TDMA: (0003/24/05) bsic: 49
Found sync burst: SNR: 16384 TDMA: (0003/08/15) bsic: 49
Found sync burst: SNR: 16384 TDMA: (0003/18/25) bsic: 49
Found CCCH burst(s): TDMA: (0003/06/39) tc:5 01 06 00 b0 00 58 47 eb 4a 92 53 40 62 84 eb 2b 2b 2b 2b 2b 2b 2b 2b si: 0x0
SI13 on wrong TC
}}}

=== Goals ===

The goal for the layer2+ application is to turn it into a complete GSM Stack for Mobilestations. This will include handling of GSM Layer2 (LAPDm, GSM 04.06), GSM Layer3 (GSM 04.08). The basic functionality will be to scan the channels, then receive information on the BCCH, listen on the paging channel, respond to paging, generate messages for the RACH and more...