The Mobile Switching Center (MSC) is the heart of 2G/3G circuit-switched services. It terminates the A-interface links from the Base Station Controllers (BSC) and handles the MM and CC sub-layers of the Layer 3 protocol from the phones (MS).

This Osmocom implementation of the MSC handles A interfaces via 3GPP AoIP in an ASP role. It furthermore implements IETF MGCP against an external media gateway, such as OsmoMGW. It does *not* implement MAP towards a HLR, but the much simpler Osmocom GSUP protocol, which can be translated to MAP if needed.