Link layer protocol and apparatus for data communication

• US 5,007,051 A
• Filed: 03/03/1989
• Issued: 04/09/1991
• Est. Priority Date: 09/30/1987
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Dolkas, Gregory D., Martin, William R.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Marcelo, Melvin
• Application Number:
  US07/319,897
• Time in Patent Office: 767 Days
• Field of Search: 370/60, 370/85, 370/94, 370/99, 370/85.1, 370/94.1, 370/110.1, 371/32, 371/33
• US Class Current: 370/235
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/225 Determination of shaping rate, e.g. using a moving window
• CPC Class Codes: H04L 47/30 in combination with information about buffer occupancy at either end or at transit nodes
• CPC Class Codes: H04L 69/324 in the data link layer [OSI layer 2], e.g. HDLC
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A method and device for controlling the transmission across a data link is disclosed. Link Layer protocol formatting in a variation on a "sliding window" protocol is implemented. In data communication equipment, a protocol controller device is described, coupling a first input/output means, for coupling to a local data terminal equipment, to a second input/output means, for coupling said local data terminal equipment to a communication link, comprising: first porting means for transferring information in to and out from said first input/output means; second porting means for transferring said information to and from said second input/output means; switching means coupled to said first porting means for controlling an input/output information transfer path through said porting means; information holding means, coupled to said first porting means and to said second porting means, for pipelining said information through said device; and controlling means, coupled to said holding means and said second porting means, for protocol formatting of said information. The present invention includes a method for controlling data transmission using an open systems interconnection model, comprising: providing link layer sliding window protocol formatting of information to be transmitted such that said protocol provides transmission error control; and providing link layer sliding window protocol formatting of information to be transmitted such that said protocol provides transmission flow control and fully decoded control information.

Claims

1. A method for controlling data transmission using an open systems interconnection model, comprising:

providing link layer sliding window protocol formatting of information to be transmitted such that said protocol provides transmission flow control.

2. A method as in claim 1 wherein

information is transmitted from a transmitter to a receiver and is transferred from the receiver to a host, and,

the link layer sliding window protocol includes control frames sent from the receiver to the transmitter, the control frames including a first state variable indicating a first frame of information to be next transferred from the receiver to the host and the control frames including a second state variable indicating a second frame of information to be next transmitted from the transmitter to the receiver.

3. A method for controlling data transmission comprising:

providing a transparent indicator within control information in a control frame from a transmitting node network controller to a receiving node network controller which is substantially compatible with the transmitting node network controller, the transparent indicator being transmitted independent of the flow of data and the transmission of the transparent indicator providing a reliable signalling capability from the transmitting node network controller to the receiving node network controller;

wherein upon receipt of the transparent indicator, data transmission state variables within the receiving node network controller are not altered.

4. The method as set forth in claim 3 additionally comprising:

providing, from the receiving node network controller to the transmitting node network controller, a reply indicator which will acknowledge the receipt of said transparent indicator;

wherein upon receipt of the reply indicator, data transmission state variables within the transmitting node network controller are not altered.

5. A method for controlling data transmission using an open systems interconnection model, comprising:

providing link layer sliding window protocol formatting of information to be transmitted such that said protocol provides transmission flow control by providing state variable information which identifies a next receiving node substantially compatible link layer protocol controller buffer to be emptied.

6. The method as set forth in claim 5, wherein providing state variable information includes:

providing a state variable in said state variable information which prevents a transmitting node link layer protocol controller from over-running a receiving node substantially compatible link layer protocol controller input buffer by indicating the receiving node input buffer status to the transmitting node; and

incrementing said state variable when the receiving node input buffer has been emptied into the receiving node data terminal equipment.

7. The method as set forth in claim 6, wherein providing state variable information further includes:

providing sliding window error control if there is continuous bidirectional information traffic on the link by said receiving node complementary link layer protocol controller incrementing said state variable to implicitly acknowledge correct receipt of information frames by said receiving node.

8. In data communication equipment, a protocol controller device coupling a first input/output means, for coupling said device to a local data terminal equipment, to a second input/output means, for coupling said device and, therefore, said local data terminal equipment to a communication link, comprising:

first porting means for transferring information in to and out from said first input/output means;

second porting means for transferring said information to and from said second input/output means;

switching means coupled to said first porting means for controlling an input/output information transfer path through said first porting means;

information holding means, coupled to said first porting means and to said second porting means, for pipelining said information through said device;

controlling means (121,

     123) coupled to said holding means and said second porting means, for protocol formatting of said information, and;

at least one control means for controlling access to said controlling means and transferring said information to and from said controlling means from said first input/out means; and

at least one device porting means for coupling said holding means to said first input/output means.

9. The device as set forth in claim 8, wherein said second porting means comprises:

transmit porting means for transferring said information to said second input/output means; and

receive porting means for transferring said information from said second input/output means.

10. The device as set forth in claim 9, wherein said switching means, control porting means and device porting means further comprises:

first programmable means, coupled to said first input/output means and said information holding means, and programmed for providing said controlling functions; and

first synchronizer means, coupling said first programmable means to said transmit porting means, for synchronizing said first input/output means clock domain and said second input/output means clock domain; and

second synchronizer means, coupling said first programmable means to said receive porting means, for synchronizing said second porting means input clock domain to said first input/output means clock domain.

11. The device set forth in claim 10, wherein said transmit porting means further comprises:

second programmable means, coupling said information holding means to said second input/output means.

12. The device as set forth in claim 11, wherein said receive porting means further comprises:

third programmable means, coupling said information holding means to said second input/output means.