INTEGRATED VOICE AND DATA COMMUNICATIONS OVER A LOCAL AREA NETWORK

摘要

A local area network (32) adapted for packet switching of standard Ethernet packets employs a communication switching module (44) to control flow of both delay-sensitive voice digital voice signals from digital telephones (36, 38, 40, 42) and non-delay-sensitive user data from PC's (14, 16) and devices (18, 20) over 10 Base-T (or 100 Base-TX) LAN segments (34). UTE adapters (46, 48, 50) at user stations are connected to both voice and data devices. Initialization procedures utilize standard Ethernet packets to set up a permanent virtual circuit between the UTE adapters and module (44). The permanent virtual circuit carries signaling and control information entered from the digital telephone keyboards. The UTE adapters and the communications switching module both incorporate a segmentation and re-assembly (SAR) means (66). The SAR means on the transmitting end of the LAN segment segments synchronous digital voice and asynchronous data and encapsulates the segments into master Ethernet packets of fixed length, and transmits the master Ethernet packets at a constant fixed rate. The SAR means on the receiving end of the LAN segment extracts the segments and reassembles the segments into synchronous voice and asynchronous data packets. Formats for master Ethernet packets (70) suitable for 10 Base-T LAN and master Ethernet packets (72) for 100 Base-TX are disclosed. Synchronous processing of voice data is accomplished internally in communication switching module (44) by time domain multiplexing over a high speed full-duplex TDM highway (64). Asynchronous processing of user data packets is accomplished internally in module (44) by high speed packet interface (62). A master oscillator in module (44) synchronizes the connected devices on the LAN through fixed rate transmission of master Ethernet packets, which serve to synchronize local clocks in the UTE adapters.