Issue with GPRS for nanoBTS: no SGSN IP sent to nanoBTS ...

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John tophut at gmail.com
Tue Apr 24 02:49:15 UTC 2012


Hi,

OK, the SGSN is running and listening/communicating on port 23000 as
specified in the config files.  I was confused because (1) I couldn't find
the IP address passed to the BTS on the Wireshark packet captures (maybe
the IP is sent as binary or not regular text), and (2), it now seems clear
the iPhone 3GS won't transmit/support GPRS even though it shows some GPRS
data in the GPRS field test modes.  Thus, with the iPhone 3GS, there was no
BTS->SGSN traffic to view (even though it has a GPRS test mode).

We are now testing with a GPRS capable phone, the LG GR500.  We can see
some initial GPRS data, but nothing more than the following.  The messages
represent what is shown upon power up of the phone, and no following GPRS
messages are sent by the phone when trying to access IP:

Here is BTS/SGSN startup:

<0011> gprs_ns.c:169 NSVCI=65534 Creating NS-VC

<0011> gprs_ns.c:169 NSVCI=65535 Creating NS-VC

<0011> gprs_ns.c:804 Creating NS-VC for BSS at 192.168.253.10:23000

<0011> gprs_ns.c:677 NSEI=65535 Rx NS RESET (NSVCI=0, cause=O&M
intervention)

<0011> gprs_ns.c:536 NSEI=101 Tx NS RESET ACK (NSVCI=101)

<0011> gprs_ns.c:863 NSEI=101 Rx NS UNBLOCK

<0012> gprs_bssgp.c:247 BSSGP BVCI=0 Rx RESET cause=Transmission capacity
modified

<0012> gprs_bssgp.c:247 BSSGP BVCI=2 Rx RESET cause=O&M intervention

<0012> gprs_bssgp.c:270 Cell 1-1-1-0 CI 0 on BVCI 2

<0012> gprs_bssgp.c:323 BSSGP BVCI=2 Rx BVC-UNBLOCK

<0012> gprs_bssgp.c:463 BSSGP BVCI=2 Rx Flow Control BVC


Here is the phone powering up:

<0012> gprs_bssgp.c:347 BSSGP TLLI=0x78fd6033 Rx UPLINK-UNITDATA

<0013> gprs_llc.c:478 LLC SAPI=1 C FCS=0x35b15fCMD=UI DATA

<0013> gprs_llc.c:742 LLC RX: unknown TLLI 0x78fd6033, creating LLME on the
fly

2nd try:

<0012> gprs_bssgp.c:347 BSSGP TLLI=0x7d3b6971 Rx UPLINK-UNITDATA

<0013> gprs_llc.c:478 LLC SAPI=1 C FCS=0x35b15fCMD=UI DATA

<0013> gprs_llc.c:742 LLC RX: unknown TLLI 0x7d3b6971, creating LLME on the
fly

I saw a note on the message board from about a year ago about handling the
unknown TLLI with a patch, but the code for gprs_llc.c has been updated
quite a bit since then.

We will try to look into it more and report back any findings, but any
pointers would be appreciated.

John



On Mon, Apr 23, 2012 at 2:22 PM, Harald Welte <laforge at gnumonks.org> wrote:

> Hi John,
>
> On Sat, Apr 21, 2012 at 12:28:53PM -0500, John wrote:
> > Note that I also did some searching and I saw one posting where the
> > configuration line "gprs mode gprs" should be "gprs mode egprs", but that
> > didn't make any difference.  Does anyone have suggestions of what might
> be
> > wrong or what I should look at?
>
> I would be helpful if you could make available a pcap file of the
> communication between BTS and OpenBSC from the point where the OML tcp
> connection is established up to the point whre you see the RSL link
> coming up.
>
> --
> - Harald Welte <laforge at gnumonks.org>
> http://laforge.gnumonks.org/
>
> ============================================================================
> "Privacy in residential applications is a desirable marketing option."
>                                                  (ETSI EN 300 175-7 Ch. A6)
>
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