On Mon, Oct 08, 2012 at 09:23:58PM +0200, Yann R. Moupinda wrote:

Hello everyone,

thanks for the ideas you gave me about how i can learn more about the communication between BSC and MSC in my sysmoBTS. Since last week i've been looking at the source codes and it's still difficult for me to follow the exchanged messages betwenn BSC and MSC. I don't have high programming skills.

well, it starts with the organisation of the sourcecode. E.g. src/libmsc contains the MSC functionality. E.g. take a look at osmo_msc.c it is glueing the "BSC API" to the MSC code. compl_layer3 (as of GSM 08.08) will be called for the first message on a newly opened RF connection. dtap will be called for every following message.

Instead of using sysmoBTS as an autonomous self-contained GSM network (NITB mode), i'd like to configure it in the BSC-only mode running the osmo-bts and osmo-bsc. I read that i will need a MSC that can provide an A-over-IP interface using SCCP-lite. I saw that the "on-waves/bsc-master" branch is implementing such a SCCP and works have been done to create a GSM0808 like API and move the MSC code inside OpenBSC over to use this API. So i was wondering how far this project has been developed yet. Do you already have any interesting results that can help me? If not, it can be also interesting for me to know how you did your tests by implementing the bsc-only mode (osmo-bsc)? Did you connect it to a real MSC or did you have anything else emulating the MSC/HLR/VLR/EIR functions?

on-waves/bsc-master is an old vendor branch, the same functionality is available in the master branch of openbsc. The src/osmo-bsc directory holds the BSC implementation. This adds GSM 08.08 parsing and message generation on top of the 'BSC API' (same interface as in osmo_msc.c but different implementation). The osmo-bsc has been used with various proprietary MSCs. There is no free MSC that will just do what you want at this point in time. I have the start of a MSC in Smalltalk but right now it is solving a non-standard usecase and is not a general MSC. Why do you need to see GSM 08.08 messages?