OpenGGSN

Terje Kristoffer Hybbestad Skow terjeks at stud.ntnu.no
Mon Apr 11 11:25:26 UTC 2016


Hi again.

I'm still having problem really getting the sgsnemu and ggsn to talk to
each other. When I use 127.0.0.1 and 127.0.0.2 as the listen and remote for
the sgsnemu and 127.0.0.2 as listen and 127.0.0.0/24 as network in the ggsn
conf, the sgsnemu says "Received echo response Received create PDP context
response. IP address: 127.0.0.2" and then nothing happens. When using two
computers, one running ggsn and one sgsnemu with the ip-addresses as
192.168.1.14 and 192.168.1.11 respectively, the sgsnemu doesn't seem to get
connented. It prints out "idletime.tv_sec 3, idleTime.tv_usec 0" over and
over, and "Echo Request timed out". The picture attached is from wireshark
on the ggsn computer.

I lookt at the pcap you send and it looks like what I would like for my
setup.

You talk mentioned using symoBTS how much does it cost? And how long is a
delivery for it?



Regards
Terje Skow


2016-03-01 12:56 GMT+01:00 Terje Kristoffer Skow <terjeks at stud.ntnu.no>:

> Thank you very much!!
>
> I will have some work getting through this, but I recon I'll have some
> more questions later.
>
> Again thank you
>
> 2016-03-01 12:39 GMT+01:00 Neels Hofmeyr <nhofmeyr at sysmocom.de>:
>
>> On Tue, Mar 01, 2016 at 11:12:01AM +0100, Terje Kristoffer Hybbestad Skow
>> wrote:
>> > The "logfile /tmp/foo" did gave an error message saying "unrecognized
>> > option".
>>
>> It seems the logfile option was added on 2014-03-23 with commit
>> 9c0ff4fafe4276396125a52c89d36967566fe08c. It may make sense if you build
>> your osmocom stack from the git sources to benefit from the latest fixes.
>>
>> See http://git.osmocom.org, specifically you'd probably want to clone
>> and build
>>
>> git://git.osmocom.org/libosmocore
>> git://git.osmocom.org/openggsn
>>
>> The build steps being for example
>>
>>    autoreconf -fi
>>    ./configure
>>    make
>>    sudo make install
>>
>>
>> > I'm going to look at DNS packets going through a GGSN to try and find
>> ways
>> > to detect DNS tunnels, do you have any recommendations how to do this?
>> > I do not have the time or resources to use real UE's so I hope to
>> simulate
>> > it on a computer using VMs or something like that.
>>
>> > I have looked at this:
>> http://openbsc.osmocom.org/trac/wiki/OpenBSC_GPRS as
>>
>> The BTS is for communicating with a phone over the air interface. Abis and
>> osmo-nitb are used for voice calls only. The SGSN is needed for real
>> networks,
>> you should be fine with the sgsnemu. So all you need is sgsnemu and
>> openggsn.
>>
>> You want to figure out how to use the sgsnemu, starting with a route into
>> the
>> tunnel device that sgsnemu opens up. So you need to look at the 'ip route'
>> commands (if you're on linux). I guess you won't need VMs; granted, it
>> might
>> make it easier to avoid circular routes (to IP addresses that should only
>> be
>> seen on the GGSN side), but certainly not a necessary prerequisite.
>>
>> I tried to ping through the sgsnemu tunnel once but saw, as I mentioned,
>> that
>> the GGSN thwarts GTP messages without a proper context being created
>> first. It
>> shouldn't be too hard, but I haven't investigated further. So you'd want
>> to
>> understand the GTP Ctrl & User messages to setup a PGP context (TEIs and
>> stuff), and figure out how sgsnemu might make your life easier in that
>> regard.
>> You probably want to read ETSI 29.060 to figure out GTP:
>>
>> http://www.etsi.org/deliver/etsi_ts/129000_129099/129060/03.19.00_60/ts_129060v031900p.pdf
>> You may find attached pcap file interesting (open in wireshark and note
>> that
>> the DNS queries are transmitted over GTP between SGSN and GGSN even though
>> wireshark tends to show only the DNS and src/dest enclosed in the GTP).
>> And again, you may look at
>> http://git.osmocom.org/openbsc/tree/openbsc/tests/gtphub/gtphub_test.c
>> about simplistic code examples of composing a PGP context conversation.
>>
>> If you'd like any more answers to questions you didn't ask ;)
>> just give us a shout...
>>
>> ~Neels
>>
>> --
>> - Neels Hofmeyr <nhofmeyr at sysmocom.de>          http://www.sysmocom.de/
>> =======================================================================
>> * sysmocom - systems for mobile communications GmbH
>> * Alt-Moabit 93
>> * 10559 Berlin, Germany
>> * Sitz / Registered office: Berlin, HRB 134158 B
>> * Geschäftsführer / Managing Directors: Holger Freyther, Harald Welte
>>
>
>
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