SS7 and Internet Protocol (IP)

The signaling system 7 (SS7) control system that is used in public switched telephone networks (PSTN) can be interconnected to other types of systems and networks using Internet Protocol (IP). Some of the interconnection issues relate to how the control of devices can be performed using dissimilar systems (e.g. mixing voice and data systems). Another key reason for interconnecting SS7 network devices to IP data networks is the cost savings that result from avoiding the access charges for connect equipment to SS7 systems and databases. This excerpted chapter from SS7 Basics, 3rd Edition provides an overview of how SS7 and Internet Protocol (IP) can be integrated. It is an introduction on how SS7 messages can be transported over IP networks (even the Internet in some cases) and how SS7 can interface with other systems (such as IP Telephony systems). It provides a description of the signaling transport (SIGTRAN) system and how it uses SCTP packet transmission protocol to reliably send telephone call control messages across connectionless data networks. Explained are the adaptation layers M3UA, M2UA, M2PA, SUA, and IUA that are used to interconnect SS7 nodes via IP systems. Overviews of SIP, MGCP, MEGACO, and H.323 IP telephone systems are provided.