Cellular Network Infrastructure » Core Network (CN) » OsmoSGSN

The following are the logs from SGSN and GGSN at the time of disconnection

From SGSN:

<000e> sgsn_libgtp.c:175 PDP Create PDP Context
<0018> iu_client.c:530 handle_co(dir=4, proc=0)
<0018> iu_client.c:530 handle_co(dir=1, proc=11)
<0018> iu_client.c:530 handle_co(dir=2, proc=1)
<0018> iu_client.c:507 handle_co_initial(dir=1, proc=19)
<0018> iu_client.c:530 handle_co(dir=2, proc=6)
<0002> gprs_gmm.c:208 GMM_ATTACH_REQ_FSM(gb_gmm_req)[0x221bd60]{Init}:
Event IU Security Command Complete received. not permitted
<0018> iu_client.c:599 Error in cn_ranap_handle_co (-1)
<0018> iu_client.c:530 handle_co(dir=1, proc=20)
<0018> iu_client.c:530 handle_co(dir=4, proc=0)
<0018> iu_client.c:530 handle_co(dir=1, proc=11)
<0018> iu_client.c:530 handle_co(dir=2, proc=1)
<0018> iu_client.c:507 handle_co_initial(dir=1, proc=19)
<0018> iu_client.c:530 handle_co(dir=2, proc=6)<0002> gprs_gmm.c:208
GMM_ATTACH_REQ_FSM(gb_gmm_req)[0x221bd60]{Init}: Event IU Security
Command Complete received. not permitted
<0018> iu_client.c:599 Error in cn_ranap_handle_co (-1)
<0018> iu_client.c:530 handle_co(dir=1, proc=20)
<0018> iu_client.c:530 handle_co(dir=4, proc=0)
<0018> iu_client.c:530 handle_co(dir=1, proc=11)
<0018> iu_client.c:530 handle_co(dir=2, proc=1)
<0023> gtp.c:2800 Packet from 192.168.27.46:2152, length: 95 content: 32
ff 00 57 00 00 00 05 11 b4 00 00 45 00 00 53 ad fc 40 00 38 06 7b 5c 17
23 dd 7e c0 a8 64 02 01 bb cf 8c 78 70 5c a6 c2 6b 46 39 80 18 01 fc 05
54 00 00 01 01 08 0a 9f 6b cd 80 ff ff 61 96 15 03 03 00 1a 6e ec c9 35
4b a9 48 c5 23 b0 fa 35 a5 d6 e7 e5 5b 95 f0 38 45 0a cf c8 97 d1 :
Unknown PDP context, GTPv1
<0023> gtp.c:2800 Packet from 192.168.27.46:2152, length: 64 content: 32
ff 00 38 00 00 00 05 11 b5 00 00 45 00 00 34 ad fd 40 00 38 06 7b 7a 17
23 dd 7e c0 a8 64 02 01 bb cf 8c 78 70 5c c5 c2 6b 46 39 80 11 01 fc dd
ce 00 00 01 01 08 0a 9f 6b cd 80 ff ff 61 96 : Unknown PDP context, GTPv1

GGSN

<0002> ggsn.c:735 PDP: Successful PDP Context
Creation: APN=internet(internet), TEIC=1, IPv4=192.168.100.2, IPv6=none
<000d> gtp.c:2761 Packet from 192.168.27.49:2152, length: 24 content: 32
1a 00 10 00 00 00 00 11 b4 00 00 10 00 00 00 05 85 00 04 c0 a8 1b 31 :
Received Error Indication
<0002> ggsn.c:372 PDP: Deleting PDP context
<000d> gtp.c:2755 Packet from 192.168.27.49:2152, length: 24 content: 32
1a 00 10 00 00 00 00 11 b5 00 00 10 00 00 00 05 85 00 04 c0 a8 1b 31 :
Unknown PDP context
<000d> gtp.c:2117 Packet from 192.168.27.49:2123, length: 52 content: 32
12 00 2c 00 00 00 01 4c 0a 00 00 0e 13 10 00 00 00 05 14 05 85 00 04 c0
a8 1b 31 85 00 04 c0 a8 1b 2a 87 00 0e 00 00 00 00 00 00 00 00 00 00 00
00 00 00 : Unknown PDP context: 1
<000d> gtp.c:2800 Packet from 192.168.27.42:2152, length: 72 content: 32
ff 00 40 00 00 00 01 00 00 00 00 45 00 00 3c 6f 51 40 00 40 06 08 fb c0
a8 64 02 d8 3a c5 8a cb 5a 01 bb 7a dc a8 09 00 00 00 00 a0 02 ff ff ce
3c 00 00 02 04 05 b4 04 02 08 0a ff ff c7 58 00 00 00 00 01 03 03 06 :
Unknown PDP context, GTPv1
<000d> gtp.c:2800 Packet from 192.168.27.42:2152, length: 72 content: 32
ff 00 40 00 00 00 01 00 01 00 00 45 00 00 3c 6f 52 40 00 40 06 08 fa c0
a8 64 02 d8 3a c5 8a cb 5a 01 bb 7a dc a8 09 00 00 00 00 a0 02 ff ff cd
42 00 00 02 04 05 b4 04 02 08 0a ff ff c8 52 00 00 00 00 01 03 03 06 :
Unknown PDP context, GTPv1
<000d> gtp.c:2800 Packet from 192.168.27.42:2152, length: 72 content: 32
ff 00 40 00 00 00 01 00 02 00 00 45 00 00 3c 6f 53 40 00 40 06 08 f9 c0
a8 64 02 d8 3a c5 8a cb 5a 01 bb 7a dc a8 09 00 00 00 00 a0 02 ff ff cb
4d 00 00 02 04 05 b4 04 02 08 0a ff ff ca 47 00 00 00 00 01 03 03 06 :
Unknown PDP context, GTPv1

As the data works much more reliably with GGSN reaction to Error Indication packets disabled, I believe it has something to do with the creation of Error Indication. But it is not limited to such because:

From 3GPP:
"if the GGSN receives a GTP-U Error Indication (from the RNC) it shall not release the related PDP context locally but the GGSN shall notify the SGSN that the RAB in RAN is invalid. This needs the GGSN to be updated."

I reviewed the related code from GGSN and currently osmo-ggsn only seems to remove the PDP context locally without acknowledging the SGSN

Attaching the relevant packet capture