A softswitch is a component used in the core network of a telecom network operator to provide call control and signalling as well as processing of media streams.
A softswitch can be used to control calls and process media on circuit switched Time-Division Multiplex (TDM) network infrastructure, packet switched Internet Protocol (IP) infrastructure, or a combination of the two. Many network operators use a softswitch with both TDM and IP capability as an essential transitional element as they go through the process of IP network transformation.
A softswitch (short for software switch) uses software on standard hardware to control phone calls, whereas older switching equipment uses dedicated, purpose-built switching hardware. In TDM network infrastructure, dedicated hardware is still required for physical TDM connections. However, in an all-IP network infrastructure using only VoIP calls, a softswitch can be virtualized entirely and run on any general-purpose hardware with Ethernet connections as part of an NFV deployment.
A softswitch combines two elements: a call agent or call feature server for call control, routing and signalling, and a media gateway or access gateway for processing media streams. These two elements can be co-located on a single piece of hardware, or located on separate hardware where one call agent or call feature server can control one or more gateways.
The softswitch concept only applies to Next Generation Network (NGN) architecture or older networks. This does not apply in the IP Multimedia Subsystem (IMS) architecture, where the concept of a softswitch doesn't exist. In an IMS network, a Media Gateway Control Function (MGCF) or Access Gateway Control Function (AGCF) controls the gateways and the two components are not conceptually aggregated into one.