GPRS and PDP Context

historical

Hi Max,

On Thu, Sep 20, 2012 at 06:00:01PM +0200, ☎ wrote:
> How to obtain as much debug information as possible?

I suggest you study the logging subsystem of libosmocore, which is used
in all of osmo-nitb/osmo-sgsn/osmo-bsc/etc.

> ggsn -d
> osmo-sgsn -d GPRS (this causes core-dump unless executed in gdb :)

It should be -d DGPRS, but I suggest you rather configure logging for
stdout or for your given telnet session via VTY.

I suggest to enable debug for NS, BSSGP, LLC, (G)MM

> The only output I got in this configuration is: [...]

This means that the SGSN and the BTS have connected successfully over
Gb/IP.

> I don't even understand if phone requested ip address?

Obtaining an IP address is the _last_ activity, after many other things.
NS/BSSGP is up.  Next you should see some GPRS ATTACH / GPRS ROUTING
AREA UPDATE.  Only after that, you can get to PDP CONTEXT ACTIVATE and
finally IP traffic.

> Is ggsn-sgsn-nitb connectivity ok?

At the point you're looking at, the GGSN is never used.  It is only
involved in PDP context establishment and transport of IP packets.

> It's good that howto briefly describes setup, but what do to when it's
> not working out of the box?

enable debugging for the respective protocol levels in osmo-sgsn using
VTY, and look at the Gb and GTP communication between the processes in
wireshark.  All protocol layers of both Gb and GTP protocol stacking are
fully supported in mainline wireshark, so all information you can
possibly want is visualized.

Regards,
	Harald
-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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