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@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@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_1290... 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@sysmocom.de http://www.sysmocom.de/
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