Packet-switched data communications system

• US 4,058,672 A
• Filed: 11/10/1976
• Issued: 11/15/1977
• Est. Priority Date: 11/10/1976
• Status: Expired due to Term

• Current Assignee: ITT Corporation (ITT, Inc.)
• Original Assignee: International Telephone and Telegraph Corporation
• Inventors: Umarji, Sudhindra R., Crager, William C., Louit, Gerard J., Griffin, Robert H.
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US05/740,681
• Time in Patent Office: 370 Days
• Field of Search: 358/256, 358/257, 178/2 R, 178/3, 178/4.1 R, 178/4.1 B, 179/3
• US Class Current: 370/394
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 12/56 Packet switching systems

Abstract

A packet-switched digital data communication system operable in a store-and-forward mode is provided for enabling substantially simultaneous full-duplex communication between a plurality of telecommunications terminals, facsimile transceivers or other data input sources over a communications network with a plurality of other terminals, facsimile transceivers or other data sources having access to the communications network and with which such communication is desired. The disclosed packetizing of data and transmission thereof in a store-and-forward mode with dynamic routing provides a highly efficient utilization of the transmission facilities, substantially error-free data transmission and a handshake capability between a wide variety of dissimilar and otherwise incompatible terminal devices such as facsimile transceivers having differing protocols, modulation techniques and other speed and code characteristics. Large blocks of data and other message information from data terminals are subdivided into data packets prior to transmission, converted into a systemwide compatible protocol, compressed, transmitted independently, time multiplexed with other packetized data from other terminals on the communications network, stored and forwarded on a priority basis and in accordance with network availability at one or more switching nodes in the network, reassembled from the received packets at a destination processor into the original data messages for coupling to the message destination terminals such that the received message is decompressed and reconverted into a format compatible with the destination terminal characteristics to enable information interchange therebetween.

Claims

1. A packet-switched data communications system comprising:

means for receiving message information from one or more message sources;

means for subdividing said message information from each of said message sources into a plurality of data packets, each of said packets including at least a portion of said message information;

means for independently transmitting said data packets over said communications system including a network of a plurality of switching nodes for selectively storing and forwarding said packets over said network in accordance with information contained by said packets; and

processing means for storing said data packets for reassembly of said packets into said message information.

2. A packet-switched data communication system in accordance with claim 1, further comprising:

means for coupling said reassembled message information to one or more message destinations.

3. A packet-switched data communications system in accordance with claim 1, wherein said data packets include at least a header portion and an information field portion, said header portion including data utilized in the storing and forwarding of said packets and said information field portion including data of variable bit length corresponding to a subdivided portion of said message.

4. A packet-switched data communications system in accordance with claim 3, wherein said header portion further includes data utilized by said processing means for reassembling said packets in such sequence that the original message information is recreated by said reassembled packets.

5. A packet-switched data communications system in accordance with claim 4, further comprising:

means for compressing said received message information into a reduced number of data bits and for coupling said compressed data to said subdividing means; and

means for decompressing said reassembled packets into said original message.

6. A packet-switched data communications system operable in store-and-forward mode for providing bidirectional communication between a plurality of source and destination data terminals at a plurality of locations over a communications network comprising:

first data processing means having coupled thereto input data from one or more of said source data terminals for subdividing said input data from each of said terminals into a plurality of packets, and having means for coupling said packets onto said communications network, said first data processing means including a first store-and-forward packet-switching means associated with said communications network for storing and independently routing said packets on said network;

second data processing means coupled to said network for reassembling said packets into said input data, said second data processing means including a second store-and-forward packet-switching means associated with said communications network for coupling said reassembled input data to one or more of said destination data terminals.

7. A packet-switched data communications system in accordance with claim 6, wherein said store-and-forward packet-switching means includes means for time division multiplexing said packets for retransmission on said communications network.

8. A packet-switched data communications system in accordance with claim 7, wherein said first and second data processing means each further include:

means for digitizing said input data from said source terminals into a protocol compatible with the operating characteristics of said destination terminals.

9. A packet-switched data communications system in accordance with claim 7, wherein said first and second data processing means each further include:

data compression means for reducing the quantity of said input data prior to the subdivision thereof into said packets; and

data expansion means for reproducing said input data after said compressed data packets are reassembled and prior to the coupling of said reassembled data to said destination terminals.

10. A packet-switched data communications system in accordance with claim 7, wherein said first and second data processing means each further include:

means for providing within each packet at least a header and an information field of a predetermined number of bytes, such that said packets are routed on said communications network in accordance with data included within said header and wherein the aggregate of said information fields of said packets, upon reassembly, corresponds to said input data.

11. A packet-switched data communications system in accordance with claim 10, wherein each of said packets further includes an error code portion appended to said information field portion of said packet.

12. A packet-switched data communications system in accordance with claim 10, wherein said store-and-forward packet switching means includes means for altering the header portion of said packet, such that the path of said packets along said network is variable by said store-and-forward switching means.

13. A packet-switched data communications system in accordance with claim 12, further including means for sequentially routing one or more of said packets to a plurality of destinations.

14. A packet-switched data communications system in accordance with claim 8, wherein said first and second data processing means each further include means for generating a voice signal at selected terminals.

15. A packet-switched communication system for transmitting digital data messages between a plurality of data terminal devices having differing operating characteristics, comprising:

first processing means for receiving data from one or more source terminal devices, each of said source terminal devices having a particular set of operating characteristics, said first processing means including;

means for converting each of said digital data messages into a digital data bit stream;

means for subdividing said digital data bit stream into a plurality of data packets, each of said packets including a portion of the message from which said packets were subdivided;

means for temporarily storing said packets; and

means for transmitting said stored packets onto a communications network;

second processing means including;

means for receiving said packets from said communications network;

means for reassembling said packets into said digital data bit stream; and

means for coupling the bit stream derived from the packets associated with each of said messages from said source terminal devices to one or more destination terminal devices such that said messages are reproduced by said destination terminal devices.

16. A packet-switched communications system in accordance with claim 15, further comprising:

at least one intermediate switching node, said switching node including;

means for receiving packets originating from one or more of said processing means;

means for temporarily storing said received packets on a priority basis; and

means for retransmitting said stored packets onto said communications network.

17. A packet-switched communications system in accordance with claim 16, further comprising:

concentrator means having a plurality of parallel inputs and at least one serial output comprising;

means for coupling the packets derived from a plurality of said first processing means to said plurality of inputs;

storage means coupled to said plurality of inputs for temporarily storing said packets;

means coupled to said storage means for serially coupling selected ones of said stored packets to said output; and

means for coupling said packets from said output onto said communications network for transmission.

18. A packet-switched communications system in accordance with claim 17, wherein said concentrator means further includes:

means for serially receiving data packets from at least one of said switching nodes;

means for coupling said packets to said storage means;

means for retrieving said stored packets from said storage means; and

means coupled to said packet retrieving means for forwarding said packets to a plurality of said second processing means.

19. A packet-switched communications system in accordance with claim 16, wherein said means for subdividing said digital data bit stream into said data packets includes protocol generation means for providing within each of said data packets a header portion and an information field portion, said header portion including at least data identifying the destination for which said packet is intended and the order of reassembly of said packet in the message from which said packet was subdivided.

20. A packet-switched communications system in accordance with claim 19, wherein each of said switching nodes further includes adaptive routing means for changing the network path over which at least some of said packets are transmitted to their intended destination and including:

means for changing at least some of the data contained in said header portion of said packets.

21. A packet-switched communications system in accordance with claim 19, wherein each of said switching nodes further includes means for routing at least some of said packets sequentially to a plurality of destinations such that at least one of said messages are transmitted to said plurality of destinations.

22. A packet-switched communications system in accordance with claim 19, wherein said means for subdividing said digital data bit stream into a plurality of data packets further includes means for appending to the information field portion of each of said packets a plurality of code bits for error correction.

23. A packet-switched communications system in accordance with claim 15, wherein said first processing means further includes:

data compression means for reducing the number of data bits in said data bit stream prior to the subdivision thereof by said subdividing means into said packets; and

wherein said second processing means further includes;

data expansion means for decompressing said compressed data contained by said packets after reassembly thereof into said data bit stream and before coupling of said data bit stream to said destination terminal device.

24. A packet-switched communications system in accordance with claim 19, wherein said protocol generation means includes:

means for imparting a system-wide compatible link, message and packet protocol to said packets such that destination terminal devices having a different protocol than said source terminal devices are adapted to reproduce said bit stream coupled thereto from said second processing means.

25. A packet-switched communications system in accordance with claim 16, further comprising:

means controlled by said first and second processing means for generating audible voice prompting at selected terminal devices in response to stored data; and

means for accessing said stored data.

26. A method for the transmission of message information from a data source terminal to a data destination terminal over a communications network, comprising the steps of:

A. coupling data representative of said message information from said data source terminal to a first processor;

B. converting said coupled data at said first processor into digital data having a predetermined protocol;

C. packetizing said digital data into a plurality of packets, each of which packets includes at least a portion of said message information, a header indicative of the destination of said packet, and information for use in later reassembly of said packets into said message information;

D. temporarily storing said packets; and

E. dynamically routing said packets onto said communications network for transmission to a second processor associated with said data destination terminal.

27. A method in accordance with the method of claim 26, wherein said temporarily stored packets are stored on a priority basis.

28. A method in accordance with the method of claim 26, wherein said temporarily stored packets are stored for predetermined time durations.

29. A method in accordance with claim 26, including the further steps of:

F. reassembling said packets at said second processing means in proper sequence into said digital data representative of said message information accordance with said predetermined protocol; and

G. coupling said message information to said second terminal for reproducion thereby in accordance with the operating characteristics of said data destination terminal.

30. A method in accordance with claim 29, including the further step of:

H. receiving said dynamically routed packets on said communications network at one or more intermediate switching nodes whereat said packets are temporarily stored and forwarded in accordance with line availability and system priority either to said second processing means or to another intermediate switching node for storing and forwarding to said second processing means.

31. A method in accordance with claim 30, including the further step of:

I. compressing said digital data at said first processor prior to said packetizing step; and

J. decompressing said reassembled packets at said second processor prior to said converting of said digital data representative of said message information.