For years industry pundits have been promising that enterprises would one day be able to use a single pipe to the carrier cloud for all of their business traffic, including VoIP. Until then, they had to make do with VoIP trunking between their premises systems.
Although this helped lower toll costs between office locations, these VoIP islands had no IP connectivity to the outside world. Consequently, enterprises still had to maintain separate circuits to the public network.
Today, the single-pipe vision is becoming a reality due to the wide acceptance and implementation of the Session Initiation Protocol (SIP).
SIP trunks are used for call control and routing, enabling enterprises to create a single, pure IP connection to carrier clouds. This is achieved through the use of 'proxies' at each end of the trunk whereby an enterprise SIP proxy peers with a carrier SIP proxy.
Voice is simply layered on top of the network as another IP application, traversing routers, switches, and border elements. SIP sets up and tears down voice calls over this logical trunk. Calls are handed off to a PSTN gateway for the last mile if they are bound for traditional phone connections.
For enterprises, SIP networking means reducing the monthly recurring cost of separate PSTN and data circuits to the premises. This also eliminates unnecessary TDM T1 interfaces on the IP PBX, since hundreds of VoIP calls can be supported through a single T1 interface.
Today, enterprises can leverage SIP for maximum cost savings and network efficiency.
