US 6,614,781 · Granted 2003-09-02

The Patent That Let Phone Companies Send Calls Over the Internet

Before this patent, phone calls traveled on one network and internet data on another, completely separate. This invention merged them—letting phone companies route voice calls through packet-switched data networks while still connecting to old-school telephone systems. It's the backbone technology that made VoIP possible at scale.

Curated and verified by the IsItPatented Editorial team

The plain-English version

What it protects

The claim covers a system architecture for routing voice and data simultaneously through a packet-switched network in a way that coexists with legacy telephone systems (PSTN). What's protected here is the specific combination of soft switch sites (which handle call processing), gateway sites (which convert between voice and data formats), and the interconnection logic that lets calls flow between internet-based connections, traditional phone lines, and customer phone systems like a PBX.

Why it matters

This patent represents a foundational technology shift in telecommunications. By enabling voice to travel over data networks rather than dedicated circuit-switched lines, it paved the way for the wholesale restructuring of how calls are routed globally. Level 3 Communications, the assignee, became a major backbone carrier for voice and data services. The patent's value lies in its architectural completeness—it didn't just show how to send voice over IP, but how to do it while maintaining compatibility with the entire existing telephone infrastructure.

Real-world use

Every time you make a VoIP call through services like Skype or your cable company's phone service, you're using network logic that traces back to this architecture—converting your voice into packets, routing them through data networks, and reassembling them at the other end.

Original USPTO abstract

The present invention describes a system and method for communicating voice and data over a packet-switched network that is adapted to coexist and communicate with a legacy PSTN. The system permits packet switching of voice calls and data calls through a data network from and to any of a LEC, a customer facility or a direct IP connection on the data network. The system includes soft switch sites, gateway sites, a data network, a provisioning component, a network event component and a network management component. The system interfaces with customer facilities (e.g., a PBX), carrier facilities (e.g., a LEC) and legacy signaling networks (e.g., SS 7 ) to handle calls between any combination of on-network and off-network callers. The soft switch sites provide the core call processing for the voice network architecture. The soft switch sites manage the gateway sites in a preferred embodiment, using a protocol such as the Internet Protocol Device Control (IPDC) protocol to request the set-up and tear-down of calls. The gateway sites originate and terminate calls between calling parties and called parties through the data network. The gateway sites include network access devices to provide access to network resources. The data network connects one or more of the soft switch sites to one or more of the gateway sites. The provisioning and network event component collects call events recorded at the soft switch sites. The network management component includes a network operations center (NOC) for centralized network management.

Patent details

Publication number: US 6,614,781
Filing date: 1998-11-20
Grant date: 2003-09-02
Assignee: Level 3 Communications, Inc.
Inventor(s): ELLIOTT ISAAC K., HIGGINS STEVEN P., DUGAN ANDREW JOHN, PETERSON JON, HERNANDEZ ROBERT L., STEELE RICK D., BAKER BRUCE W., TERPSTRA RICH, MITCHELL JONATHAN S., WANG JIN-GEN, STEARNS HAROLD, ZIMMERER ERIC, WAIBEL RAY, OWEN KRAIG, LEWIS SHAWN M.
CPC class: H04L12/6418

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