CS Fallback in NextEPC

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Harald Welte laforge at gnumonks.org
Thu Jul 11 16:47:09 UTC 2019


Hi Sukchan,

On Fri, Jul 12, 2019 at 12:14:51AM +0900, Sukchan Lee wrote:
> Today I've added CS Fallback and released NextEPC v0.5.0

Thanks a lot!

> So, I'd just like to test this part with Osmocom project, but it seems to
> be a difficult task. The reason is why I have little knowledge about 2G/3G.
> Nevertheless, I will try to do it

I advise you to not spend too much time on it until we can provide you
with a set of configuration and instructions on how to configure this,
instead of spending a lot of time in trial and error.  I think we can
save you some time there.

A good starting point would be to use the nightly builds for Ubuntu or Debian,
(see https://osmocom.org/projects/cellular-infrastructure/wiki/Nightly_Builds)
and try to follow the general instructions of https://osmocom.org/projects/cellular-infrastructure/wiki/Osmocom_Network_In_The_Box.  The goal would be to create a network with two phones/IMSIs
where you can have a 2G-to-2G voice call first.   Only once that works, the
LTE neighbor cell information and SGs configuration can be added.

You will need the following parts for a minimal 2G setup:

* osmo-trx + osmo-bts-trx (if using SDR like B2x0)
* osmo-bsc (RR)
* osmo-msc (MM + CC)
* osmo-hlr
* osmo-stp (for SS7/SIGTRAN between BSC and MSC)
* osmo-mgw (for RTP audio streams; one instance can be shared between BSC and MSC)

All of the above can run on a single machine

> BTW, I don't know if there is anyone who wants to integrate this big thing.

For sure we want to, and we also know there are users out there who want to.

> Even though I'm not sure if this will help, but let me introduce the
> configuration of the NextEPC.

Thanks, this is useful.  We'll try to to set this up accordingly, but it may
take some time.

Philipp (Cc) has been developing most of the SGs interface on the Osmocom
side, he can help you (here on this list and by direct e-mail) with any related
issues.

> FYI, I also attach the pcap that I run with nextepc simulator as below.

Thanks, I'd like to ask Philipp to review this and report if it reflects his
expectations about the SGs interface procedures.

btw/unrelated: I've been hacking a lot on TTCN-3 tests for the MME, and
I've managed to get the way into NAS (EMM/ESM) and am getting all the
way up to a Attach Reject (see attached pcap).  As I'm only simulating
S1AP and SGsAP so far (and not diameter), it's expected that the attach
will be rejected.  I guess I'll start with using nextepc-hss first, and
add diameter support to the tests only in a later step.

Regards,
	Harald

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