Hello, I am trying to set up an OpenBSC based GSM network. The GSM part was easy and relatively quick to do, but I have a problem with GPRS. I have read the documentation for OpenSGSN (http://openbsc.osmocom.org/trac/wiki/) and OpenGGSN (man page). After a couple of days searching for more information and trying whatever came to my mind, GPRS still does not work.

BTS is ip.access nanoBTS, using IP address 192.168.2.3 (was set up like that, I got it second hand). It is connected to eth1 (192.168.2.1). The PC is running osmo-nitb, osmo-sgsn and ggsn (started in reverse order). Interface eth0 is internet connection (behind NAT).

********** bash-4.1# ifconfig eth0 Link encap:Ethernet HWaddr 00:22:15:99:86:2E inet addr:192.168.110.34 Bcast:192.168.110.255 Mask:255.255.255.0 inet6 addr: fe80::222:15ff:fe99:862e/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:22233 errors:0 dropped:1314 overruns:0 frame:0 TX packets:4200 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:4119511 (3.9 Mb) TX bytes:514598 (502.5 Kb) Interrupt:20 Memory:f9fc0000-f9fe0000

eth1 Link encap:Ethernet HWaddr 00:E0:7D:D6:7D:2D inet addr:192.168.2.1 Bcast:192.168.2.255 Mask:255.255.255.0 inet6 addr: fe80::2e0:7dff:fed6:7d2d/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:7311 errors:0 dropped:0 overruns:0 frame:0 TX packets:7211 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:630759 (615.9 Kb) TX bytes:445274 (434.8 Kb) Interrupt:17 Base address:0xe800

lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:8 errors:0 dropped:0 overruns:0 frame:0 TX packets:8 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:480 (480.0 b) TX bytes:480 (480.0 b)

lo:1 Link encap:Local Loopback inet addr:192.168.3.2 Mask:255.255.255.0 UP LOOPBACK RUNNING MTU:16436 Metric:1

lo:2 Link encap:Local Loopback inet addr:192.168.3.3 Mask:255.255.255.0 UP LOOPBACK RUNNING MTU:16436 Metric:1

tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:192.168.254.1 P-t-P:192.168.254.1 Mask:255.255.255.0 UP POINTOPOINT RUNNING MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:500 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) **********

bash-4.1# cat /proc/sys/net/ipv4/ip_forward 1 ********** I have also added a rule to iptables: iptables -A POSTROUTING -s 192.168.254.0/24 -t nat -o eth0 -j MASQUERADE **********

Here are my configuration files: ********** GPRS section of nitb.conf: ********** gprs mode gprs gprs routing area 0 gprs cell bvci 2 gprs nsei 101 gprs nsvc 0 nsvci 101 gprs nsvc 0 local udp port 23000 gprs nsvc 0 remote udp port 23000 gprs nsvc 0 remote ip 192.168.2.1

********** sgsn.conf: ********** ! ! Osmocom SGSN configuration ! line vty no login ! sgsn gtp local-ip 192.168.3.2 ggsn 0 remote-ip 192.168.3.3 ggsn 0 gtp-version 1 ! ns timer tns-block 3 timer tns-block-retries 3 timer tns-reset 3 timer tns-reset-retries 3 timer tns-test 30 timer tns-alive 3 timer tns-alive-retries 10 encapsulation udp local-ip 192.168.2.1 encapsulation udp local-port 23000 encapsulation framerelay-gre enabled 0 ! bssgp !

********** ggsn.conf: ********** pidfile /var/run/ggsn.pid statedir /var/lib/ggsn/ listen 192.168.3.3 net 192.168.254.0/24 dynip 192.168.254.0/24 timelimit 0

I am using Wireshark with patches from openbsc git applied. GSM calls and SMS work fine. BTS is able to connect to SGSN, as can be seen from the output:

********** rado@openbsc:~$ osmo-sgsn -c sgsn.conf <0011> gprs_ns.c:151 NSVCI=65534 Creating NS-VC <0011> gprs_ns.c:151 NSVCI=65535 Creating NS-VC <0011> gprs_ns.c:738 Creating NS-VC for BSS at 192.168.2.3:23000 <0011> gprs_ns.c:620 NSEI=65535 Rx NS RESET (NSVCI=0, cause=O&M intervention) <0011> gprs_ns.c:488 NSEI=101 Tx NS RESET ACK (NSVCI=101) <0011> gprs_ns.c:797 NSEI=101 Rx NS UNBLOCK <0012> gprs_bssgp.c:246 BSSGP BVCI=0 Rx RESET cause=Transmission capacity modified <0012> gprs_bssgp.c:246 BSSGP BVCI=2 Rx RESET cause=O&M intervention <0012> gprs_bssgp.c:269 Cell 230-10-1209-0 CI 2984 on BVCI 2 <0012> gprs_bssgp.c:322 BSSGP BVCI=2 Rx BVC-UNBLOCK <0012> gprs_bssgp.c:462 BSSGP BVCI=2 Rx Flow Control BVC

********** When trying to use GPRS from mobile phone: ********** <0012> gprs_bssgp.c:346 BSSGP TLLI=0x7ed21cb5 Rx UPLINK-UNITDATA <0013> gprs_llc.c:478 LLC SAPI=1 C FCS=0x17cd30CMD=UI DATA <0013> gprs_llc.c:741 LLC RX: unknown TLLI 0x7ed21cb5, creating LLME on the fly <0012> gprs_bssgp.c:346 BSSGP TLLI=0x7ed21cb5 Rx UPLINK-UNITDATA <0013> gprs_llc.c:478 LLC SAPI=1 C FCS=0x17cd32CMD=UI DATA <0012> gprs_bssgp.c:346 BSSGP TLLI=0x7ed21cb5 Rx UPLINK-UNITDATA <0013> gprs_llc.c:478 LLC SAPI=1 C FCS=0x17cd4cCMD=UI DATA

and so on until phone timeouts.

The problem is in my opinion between SGSN and GGSN, as no data is transferred through the tunnel (or the lo interface). But I checked the settings multiple times and tried other configurations (alias for eth1). Openbsc, openggsn, libosmocore, libosmo-abis are all compiled from git repositories.

I do not understand what I am doing wrong and I am out of options. So I am asking for help. Thank you for your time.

Rado Krkos