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

• US 20020064137A1
• Filed: 11/30/2000
• Published: 05/30/2002
• Est. Priority Date: 11/16/2000
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Garakani, Mehryar Khalili, Wildfeuer, Herbert M., Melhorn, Nathan R., Prewarski, Marcus
• Granted Patent: US 7,113,501 B2
• Time in Patent Office: Days
• US Class Current: 370/278
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 5/1438 Negotiation of transmission parameters prior to communication modified according to link quality H04L1/0001

Abstract

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.

Claims

1. A method of synchronizing two de/compression modems in a voice frame network, each of the modems each being connected with a corresponding gateway to form a corresponding segment, the method comprising:

terminating the physical layer at either end by 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 said not-ready message-sending and sending a ready message to a corresponding modem, whereby synchronized data transmissions between the modems commences.

2. The method of claim 1, wherein the not-ready message is a receiver-not-ready (RNR) message compliant with the ITU-T V.42 protocol and wherein the ready message is a receiver ready (RR) message compliant with the ITU-T V.42 protocol.

3. The method of claim 1 which, after said signaling and upon occurrence of a destructive break condition in either of the segments, further comprises:

relaying the occurrence of the destructive break condition from a segment where it is detected to the other segment.

4. The method of claim 1 which, after said signaling and upon receipt at either gateway from a corresponding modem of an initiate data transfer command, further comprises:

relaying the initiate data transfer command from a segment where it is detected to the other segment.

5. The method of claim 4 wherein the initiate data transfer command is a Set Asynchronous Balanced Mode Extended (SABME) message compliant with the ITU-T V.42 protocol.

6. The method of claim 5 wherein the synchronized data transmissions between the modems utilizes a reliable transport.

7. Apparatus for synchronizing compression and decompression between two endpoint modems linked over a voice frame network, the apparatus comprising:

a negotiation mechanism for bringing up physical and data link layers on a segment associated with a first one of the two endpoint modems and an associated gateway as answerer and for bringing up physical and data link layers on another segment associated with a second one of the two endpoint modems and associated gateway as originator;

a signaling mechanism associated with each gateway responsive to said negotiation mechanism for signaling the other gateway and for awaiting a signal therefrom;

a command mechanism for sending a receiver ready command to the two endpoint modems; and

a commencement mechanism responsive to said command mechanism for commencing data transmission/reception between the two endpoint modems characterized by synchronized data compression and decompression.

8. The apparatus of claim 7 which further comprises:

a detection mechanism for detecting a destructive break condition or receipt of an initiate data transfer command;

a relaying mechanism associated with each gateway responsive to said detection mechanism upon either such detection for relaying the destructive break condition to the other gateway upon detection of the same and for relaying the receipt of the initiate data transfer command upon detection of the same; and

a data discard mechanism responsive to said relaying mechanism for discarding data until a modem initialization responsive to the condition and/or the command receipt is completed.

9. The apparatus of claim 8, wherein the receiver ready command is a receiver ready (RR) message compliant with the ITU-T V.42 protocol.

10. The apparatus of claim 8 in which upon receipt at either gateway from a corresponding modem of an initiate data transfer command, said relaying mechanism associated with each gateway responsive to such receipt further relays the initiate data transfer command from a segment where it is detected to the other segment.

11. The apparatus of claim 10, wherein the initiate data transfer command is a Set Asynchronous Balanced Mode Extended (SABME) message compliant with the ITU-T V.42 protocol.

12. The apparatus of claim 8, wherein said negotiating mechanism during said negotiations of the physical and data link layers sends from either gateway to an associated modem in response to any poll command therefrom a not-ready message.

13. The apparatus of claim 12, wherein the not-ready message is a receiver-not-ready (RNR) message compliant with the ITU-T V.42 protocol.

15. The computer-readable medium in accordance with claim 15, which computer-readable medium further comprises:

instructions for relaying an occurrence of a destructive break condition from a segment where it is detected to the other segment.

16. The computer-readable medium in accordance with claim 15, which computer-readable medium further comprises:

instructions for relaying an initiate data transfer command from a segment where it is detected to the other segment.

18. The apparatus of claim 17 which further comprises:

means for relaying a destructive break condition detected at either gateway to the other gateway.

19. The apparatus of claim 18 which further comprises:

means for relaying an initiate data transfer command received at either gateway to the other gateway.

20. The apparatus of claim 19, wherein the not-ready message is a receiver-not-ready (RNR) message compliant with the ITU-T V.42 protocol, wherein the ready message is a receiver ready (RR) message compliant with the ITU-T V.42 protocol and wherein the initiate data transfer command is a Set Asynchronous Balanced Mode Extended (SABME) message compliant with the ITU-T V.42 protocol.

14. A computer-readable medium containing a program for synchronizing two de/compression modems in a voice frame network wherein the modems each are connected with a corresponding gateway to form a corresponding segment, the program comprising:

instructions for terminating the physical layer at either end by the corresponding gateways;

instructions for negotiating at either gateway a physical layer and error-correcting data link layer with the corresponding modem;

instructions for sending from either gateway to an associated modem in response to any poll command therefrom a not-ready message;

instructions for signaling the other gateway when physical layer and error-correcting data link layer negotiations have been completed; and

instructions for halting the not-ready message-sending and for sending a ready message to a corresponding modem when each gateway has signaled the other that negotiations have been completed.

17. Apparatus for synchronizing compression and decompression between two endpoint modems linked over a voice frame network, each of the modems being connected with a corresponding gateway to form a corresponding segment, the apparatus comprising:

means for terminating the physical layer at either end by the corresponding gateways;

means for negotiating at either gateway a physical layer and error-correcting data link layer with the corresponding modem;

means for sending from either gateway to an associated modem in response to any poll command therefrom a not-ready message;

means for signaling the other gateway when physical layer and error-correcting data link layer negotiations have been completed; and

means active when each gateway has signaled the other that negotiations have been completed for halting the not-ready message-sending and for sending a ready message to a corresponding modem, whereby data transmissions between the modems commences that is characterized by synchronized data compression and decompression.