What is Signaling?
“Signaling is a means by which elements of the telephone network exchange information”. Today, on the public switched telephone network, Signaling performs the function of putting the information required to set up and manage telephone calls in a separate “Out of Band” network rather than within the same network. In other words, signaling (control) information travels on a separate channel rather than within the same channel as the telephone call. Historically, the signaling for a telephone call has used the same voice circuit that the telephone call traveled on (this is known as in-band signaling).

SS7
The development of the standard signaling system 6 and the subsequent signaling system seven (SS7) network was pivotal to the overall evolution of the public network and the availability of advanced telephony services. The SS7 network acts as the backbone for the Advanced Intelligent Network (AIN), provides access to AIN features, allows for efficient call setup and teardown and interconnects thousands of telephony providers under a common signaling network.

Some of the services that SS7 is used for are listed below:

• Setting up and managing the connection for a call
• Tearing down the connection when the call is complete
• Billing
• Managing call forwarding, calling party name and number display, three-way calling, and other Intelligent Network (IN) services
• Toll-free (800 and 888) and toll (900) calls
• Wireless as well as wireline call service including mobile telephone subscriber authentication, personal communication service, and roaming

SIGTRAN
SS7 Signaling Transport over IP
IP networks will play an important role as carriers of signaling traffic for the Next Generation Network. Traditionally, signaling has been transmitted over a dedicated network using specialized software and hardware. By using IP for signaling traffic, operators can achieve substantial cost savings. It also provides opportunities for developing new IP-based services by combining the strength of both the Internet and legacy Networks. Integration and interconnection of equipment from different vendors will also be much easier with standardized IP connectivity.

SS7 signaling can now be transmitted over an IP network by using the IETF SIGTRAN protocols. These protocols enable operators to simplify network operations and maintenance because a dedicated signaling network is no longer needed. SS7 over IP can also be used to complement the existing signaling network for the following:

1. Long distance SS7 backhaul (MACH7-SPOP)
2. High bandwidth requirements. (MACH7-iSTP)

Converging Legacy and Next Generation Signaling
There is an on-going integration of circuit networks and IP networks. Fixed and mobile telephone network operators are designing all–IP architecture, which includes support for signaling system 7 (SS7, SIGTRAN) signaling protocols. IP provides an effective way to transport user data and for operators to expand their networks and build new services. Mass popularization of communication services contribute to the rapid growth of signaling networks. As such, more scalable and flexible networks, such as the Internet and its technologies, are needed. The benefits of using an IP network has made it necessary that Network Elements for Wireless/Wireline/VoIP require dual stacks ( Signaling Gateway’s), and for SS7 to interface with the legacy systems and SGTRAN for the Next Generation Network.