Cisco Technology, Inc.

Occam Networks

Marcus Prewarski

Mehryar Khalili Garakani

Nathan Richmond Melhorn

Herbert Michael Wildfeuer

Mark Rumer

William Sloan

The present invention is a two-pass method and apparatus for achieving maximal data compression for a voice frame modem relay channel between two endpoint modems. The method includes transitioning the channel from a voice mode to a modem relay mode of operation; negotiating maximal compression parameters for either of two endpoint segments; communicating the same from one segment to the other; and then negotiating maximal end-to-end data compression parameters based upon the negotiated endpoint segment compression parameters. The end-to-end negotiation preferably involves re-negotiating one of the endpoint segments. The apparatus includes a dual first-pass negotiation mechanism for independently determining the maximal data compression capability of each segment; an end-to-end data compression capability determination mechanism for determining the maximal end-to-end data compression capability based upon the independently determined capability of each segment; and a second-pass negotiation mechanism for establishing the determined maximal end-to-end data compression capability for the channel.

Two-pass method and apparatus for achieving maximal data compression for a modem relay mode of operation in a voice frame network

Method and apparatus for synchronizing two de/compression modems, e.g. V.42bis modems, in a voice frame network, the modems each being connected with a corresponding gateway to form a corresponding segment, are described. The method includes terminating the physical layer at either end of the corresponding gateways; negotiating at either gateway a physical layer and error-correcting data link layer with the corresponding modem; sending from either gateway to an associated modem in response to any poll command therefrom a not-ready message; signaling the other gateway when physical layer and error-correcting data link layer negotiations have been completed; and when each gateway has signaled the other that negotiations have been completed, halting the not-ready message-sending and sending instead a ready message to a corresponding modem, whereby synchronized compressed and decompressed data transmissions between the modems commences on a reliable transport. Preferably, thereafter, and upon occurrence of a destructive break condition or receipt at either gateway from a corresponding modem of an initiate data transfer command, such condition or receipt is relayed from a segment where it is detected to the other segment, thereby maintaining synchronization between the modems. Preferably, the messages and commands are compliant with the ITU-T V.42 protocol.

Synchronization of V42bis de/compression for V34/V42 modem relay method and apparatus

A local time of a broadband loop carrier terminal is synchronized to a network time received from a source external to the broadband loop carrier terminal by comparing the local time to the network time to generate an error offset, and adjusting the local time based on the error offset. The network time may be received in response to a Network Time Protocol (NTP) poll transmitted by the broadband loop carrier terminal. In some cases, the poll is transmitted over a communication medium using an asynchronous packet protocol, such as Ethernet or TCP/IP. In one embodiment, the local time is based on the output of a local oscillator (e.g., a voltage controlled oscillator), the frequency of which may be adjusted using control logic which uses a filtered version of the error offset along with a factory calibration and/or temperature compensation to produce a control voltage to control the oscillator frequency.

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Santa Barbara, CA, United States of America

Marcus Prewarski