PDF of this tutorialThe vision for a next-generation switching platform is a distributed architecture in which media gateway/bearer transport platform, signaling, call control, and application elements are divided into separate logical network components (see Figure 3), communicating with one another through the use of intraswitch protocols such as Megaco, media gateway control protocol (MGCP), and SCTP/M3UA. This distributed model allows service providers to scale their network to support hundreds of thousands of subscriber ports per node. In this concept, voice traffic is directed between the traditional voice network and the new packet-based networks by the media gateway. The call control is handled by a softswitch, and the features and services are handled by an application platform. In reality, the softswitch (or call control platform) may support some of the more popular services without requiring a separate application platform. An example of this type of service is 7/10 digit routing, which would be handled directly by the call control platform. Other examples of where the application platform may not be involved are caller name delivery, local number portability (LNP), and E-800 service. These services are already implemented in the PSTN using service control points (SCPs). In these cases, the call control platform will send intelligent network (IN)/transactional capabilities application part (TCAP) queries over the signaling system 7 (SS7) network to existing SCPs.
Figure 3. Elements of a Next-Generation Switching Platform
Some vendors enable one or more of these logical network elements to be deployed on the same physical platform. There are some inherent advantages to this "integrated" model especially with platforms that support up to 100,000 subscriber ports (DS–0s) per bearer platform/media gateway, and allow efficient execution of the softswitch and signaling gateway software. Benefits also include cost savings and deployment and operation simplicity. In the "integrated" model, the need for intraswitch protocols such as Megaco and MGCP are not required; however interswitch protocols such as RTP/UDP/IP (for MG to MG) and BICC (for SG to SG) are always required for interoperability with the other ends. See Figure 4 for relevant inter-switch protocols.
Figure 4. Interoperability: Call Control, Signaling, and Bearer Platforms
