Convergence Switching
Switching is a series of functions that establish and control media paths between multiple network elements to transmit content. The Public Switching Telephone Network's (PSTN's) main focus has been to deliver voice calls using circuit-switching technology across digital switches with inter-machine trunks between them, carrying digitized voice using Time Division Multiplexing (TDM) channels.

Some of the switching services include:

• Toll Free Dialing
• E911
• CLASS services (such as Caller ID, Call Forwarding, Call Waiting)
• VPN
• Centrex
• Number Portability and many others.

Capabilities of the PSTN have proliferated with the adoption of SS7 signaling and the Intelligent Network (SCP, STP etc.) architecture evolving around it.

Savvy carriers seek to leverage their installed backbones to deliver high-quality, cost-effective voice, data and video services. With a converged switching architecture, carriers can exploit the unique capabilities of IP to fashion profitable Next Generation voice/data/video alternatives. Convergence switching is the means for carriers to marry the reliability and scope of their PSTN investments to the cost and operational efficiencies of their Next Generation Network.

In time, carriers will gradually augment or replace their switched-circuit networks with an IP-based infrastructure that leverages general purpose computing platforms, standards-based open interfaces, and signaling protocols, such as Session Initiation Protocol (SIP) and Signaling Transport (SIGTRAN). The migration from circuit to packet-based networks, relative to the network signaling required for switching, opens the door to new possibilities. Carriers and equipment providers along with Signaling require a Call Agent (MGC/SG) to act as a bridge between the Legacy and Next Generation Networks, converting signaling from ISUP/TCAP (SS7), to SIP/H323, and vice versa.

The Dilemma
The solution to this dilemma is the converged switching architecture—the merger of IP switching technology with SS7 intelligence. .

Convergence switching solutions should include full-featured SS7 support and standard telephony interfaces and fully interoperate with the existing PSTN infrastructure to enable all of the voice features to which users are accustomed. Solutions that are based on IP can deliver Next Generation features/services, while distributed SS7 processing ensures that signaling scales as rapidly and economically as port count.

A convergence switch that supports the consolidation of SS7 links from multiple IP endpoints, offers efficient and centralized operations and billing management.
In summary, a converged switching architecture removes the remaining barriers to the cost-effective convergence of voice, data and video by delivering the following:

• telephony-grade reliability
• full SS7 signaling integration
• full IP (SIP/H323) signaling integration
• call control using MGCP/MEGACO
• scalability of both port count and SS7 signaling power
• an open architecture for rapid, simplified service deployment

A converged architecture can leverage existing investments in infrastructure, like traditional circuit-switching equipment and Intelligent Network, while supporting IP enabled features and services. The architecture can unify the series of multiple overlay networks that is necessary to communicate today.