Having a private stand-alone GSM network is great, but most often people want to interface this network somehow to other networks, whether private or public. In the past, many people did so using lcr (Linux Call Router). LCR is a very powerful soft-PBX for Linux. However, in many cases a thin gateway to SIP is all that's required. So in order to reduce the complexity and to avoid having to understand and configure yet another program, osmo-sip-connector has been developed. This talk explains the MNCC interface of OsmoNITB and shows you how to add osmo-sip-connector to interface to external SIP PBXs or SIP providers using SIP trunking.