Network Convergence

The evolution and convergence towards a common core in­frastructure is sometimes called the New Generation Net­work (NGN) architecture, see figure 10.

This network evolution is supported by techniques for separation of control and switching such as the media gate­way control protocol H.248. Call session control functions and protocol collections such as H.323 enable call setup including coded and compressed voice calls and choice of coding standard to be used. The Session Initiation Protocol (SIP) has a similar but more limited scope for the setup of communication sessions between two parties and selection of coding standard using the Session Description Protocol (SDP).

The IP Multimedia Subsystems (IMS) defined by the European Telecommunications Standards Institute (ETSI) and the 3rd Generation Partnership Project (3GPP) allow video and other media forms to be exchanged and charged on a session by session basis from peer to peer in a way similar to classic phone calls.

So-called “softswitches” or media gateway controllers in­clude call session control functions for handling of voice calls and other session oriented services. They are also re­sponsible for that sessions can be connected via a physical switch or media gateway (MGW) and handle the signaling between network nodes and other networks. The call ses­sion control function establishes a call or session, and fur-

Figure 10. Converged network ar­chitecture with decoupling of access, transport, control and service func­tions.

ther manages its reserved connection path resources end to end, for example through an ATM or IP backbone net­work and for media stream processing. The MGM provide physical switching and interfaces to access nodes and other networks.

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