Terje Kristoffer Hybbestad Skow terjeks at
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 and as the listen and remote for
the sgsnemu and as listen and as network in the ggsn
conf, the sgsnemu says "Received echo response Received create PDP context
response. IP address:" and then nothing happens. When using two
computers, one running ggsn and one sgsnemu with the ip-addresses as and 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

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

Terje Skow

2016-03-01 12:56 GMT+01:00 Terje Kristoffer Skow <terjeks at>:

> 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>:
>> 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, specifically you'd probably want to clone
>> and build
>> git://
>> git://
>> 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:
>> 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:
>> 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
>> 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 - 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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