Table of Contents:

Definition and Overview

1. SIGTRAN Overview

2. Why Develop a New Transport Protocol? — The Motivation

3. Stream Control Transport Protocol (SCTP)

4. Message Transfer Part 2 Peer-to-Peer Adaptation (M2PA)

5. M2UA

6. M2PA and M2UA Comparison

7. Message Transfer Part 3 User Adaptation (M3UA)

8. SUA

9. SUA and M3UA Comparison

10. Conclusion

Self-Test

Glossary

PDF of this tutorial

Definition
Signaling Transport (SIGTRAN) is a new set of standards defined by the International Engineering Task Force (IETF). This set of protocols has been defined in order to provide the architectural model of signaling transport over IP networks. As such, only the signaling solutions are defined in this tutorial; transport of bearer traffic is not covered.

Overview
The communication industry is going through a period of explosive change that is both enabling and driving the convergence of services. Data is becoming more significant as a proportion of traffic compared to voice. Operators are seeking ways to consolidate voice and data traffic, platforms, and services in order to reduce the operational, maintenance, and initial cost of the network. With a number of technological solutions to choose from, Internet protocol (IP) is now considered the most promising media on which to build the new integrated services. 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) 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, including short message services (SMS), 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 in comparison to a legacy time division multiplex (TDM)–based network include:

• Ease of deployment—When using signaling gateways (such as access service group [ASG]), there is no need to disrupt the existing SS7 network, and future enhancements are transparent.
• Less costly equipment—There is no need for further expensive investments in the legacy signaling elements.
• Better efficiency—SIGTRAN over an IP network doesn't require the physical E1/T1 over synchronous digital hierarchy (SDH) rings. Using new technologies like IP over SDH and IP over fiber, for instance, can achieve much higher throughput.
• Higher bandwidth—SIGTRAN information over IP does not constrain to link capacity as it does in the SS7 network. The IP network is much more flexible than the TDM-based legacy network.
• Enhanced services—Implementing a core IP network facilitates a variety of new solutions and value-added services (VAS).

Figure 1. Sample Implementation for Signaling Transport over IP

Figure 1 depicts the diversity of solutions achieved by using signaling transport protocols. Using SIGTRAN protocols such as an MTP3 user application (M3UA) and a signaling connection control part user application (SUA), the application vendor (i.e Short Message service center [SMSC], IP—home location register [IP-HLR], and so on) only has to develop the application layer and does not have to deal with the complex SS7 interfaces. By making the network introduction complexity and integration problem much shorter, the time for marketing these new applications will be much faster. SS7 over IP also solves the throughput limitation that was inherited from the SS7 standards, thus allowing high-end machines like SMSC, HLR, and so on to be able to support heavy SS7 traffic needs.

By using signaling gateways, both legacy and new equipment can seamlessly continue to operate over high bandwidth, scalable and available IP–based core network, instead of burdening the TDM–based legacy SS7 network.