Common channel signalling routing method based on the MTP3 service indicator octet (SIO) code

摘要

UMTS's protocol signalling messages are routed between signalling points associated to the various network elements of the mobile radio network. Each message includes an originating point code field (OPC A) for indicating the originating signalling point, a destination point code field (DPC B) for indicating the destination signalling point, and a service information code field (SIO) for distributing the message to an addressed user part, such as: ATM Adaptation Layer AAL2 / AAL3 (disclosed in the relevant 3GPP Technical Specifications), or Signalling Connection Control Part SCCP (disclosed in the relevant ITU-T standards), or other known parts. Signalling protocols of two Application Parts only are considered: the Radio Access Network Application Part (RANAP), and the Access Link Control Application Part (ALCAP). An originating signalling point is associated to a radio network controller (RNC) and a destination signalling point is associated to the MSC. The radio network controller (RNC) originates both RANAP and ALCAP messages and put them on a Link set directed to the Core Network. The RANAP and ALCAP messages have a common destination point code field (DPC B) indicating MSC, and different service information code, namely: SCCP for RANAP, and ATM Adaptation Layer AAL2 / 3 for ALCAP. A media gateway (MGW) placed before the MSC receives both the RANAP and ALCAP messages and, on the basis of the service indicator code, routes RANAP to the MSC and ALCAP to the media gateway (MGW) (fig.8).