Simplified recovery of damaged frames in a communication link

• US 5,938,786 A
• Filed: 11/30/1995
• Issued: 08/17/1999
• Est. Priority Date: 11/30/1995
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gregg, Thomas Anthony
• Primary Examiner(s): Grant, William
• Assistant Examiner(s): Marc, McDieunel, Marc, McDieunel
• Application Number:
  US08/565,598
• Time in Patent Office: 1,356 Days
• Field of Search: 371/32, 395/200.1, 395/200.13, 395/825, 361/45
• US Class Current: 714/748
• CPC Class Codes: H04L 1/1835 Buffer management
• CPC Class Codes: H04L 1/1851 using multiple timers
• CPC Class Codes: H04L 1/1874 Buffer management
• CPC Class Codes: H04L 1/1883 using multiple timers

Abstract

An apparatus and method is provided for asynchronously transmitting data across fiber optical cables in a serial manner. Frames are provided as a mechanism to transmit associated data over a serial link and to tie the data being transmitted to a particular buffer set. Each outstanding request for each buffer set is individually timed to detect lost frames, and each buffer set maintains a state that keeps track of the progress and sequence of received frames. When transmission errors occur in the frames, the errors may affect only the information field in which case there is enough information in the header to identify the frame. If a frame is damaged, any outstanding operations for the affected buffer set are cleared, and any commands are brought to a logical ending point. The computer system which originates the frames is then notified of the specific nature of the error, and which information is supplied to help the originating computer system efficiently conclude the recovery procedure.

Claims

1. A method for direct transmission of frames between an originator at a first location and a recipient at a second location, said frames having at least a link-control field, said method for transmitting comprising the steps of:

transmitting from said first location a message command frame having an information field specifying a command;

receiving said transmitted message command frame at said second location;

discarding said received message command frame upon the determination that an error is present in said information field of said message command frame and replying to said first location by transmitting thereto a frame indicating an error status in the received message command frame; and

notifying said originator of the resulting message error status.

2. The method of claim 1 wherein said message command frame includes an indication (A-bit) in said link-control field that a data frame is to be sent and wherein there is further included the following steps:

after said transmitting step, transmitting from said first location a data frame having an information field containing data for transmission to said second location;

receiving said data frame at said second location, the transmission of said data frame having been indicated by said previously transmitted A-bit; and

discarding said data frame upon detection that an error had been present in the information field of said message command frame.

3. A method for direct transmission of frames between an originator at a first location and a recipient at a second location, said frames having at least a link-control field, said method for transmitting comprising the steps of:

transmitting from said first location a message command frame having an information field specifying a command;

receiving said transmitted message command frame at said second location;

after said step of transmitting said message command frame, transmitting from said first location a data frame having an information field containing data for transmission to said second location, said message command frame having included an indication (A-bit) in said link-control field that said data frame was to be sent;

receiving said data frame at said second location, the transmission of said data frame having been indicated by said A-bit in said message command frame;

discarding said data frame upon detecting that an error is present in said link-control field of said message command frame;

discarding said received message command frame upon the determination that an error is present in said link-control field of said message command frame and replying to said first location by transmitting thereto a frame indicating an error in the received message command frame; and

notifying said originator of the resulting message status.

4. A method for direct transmission of frames between an originator at a first location and a recipient at a second location, said frames having at least a link-control field, said method for transmitting comprising the steps of:

transmitting from said first location a message command frame having an information field specifying a command and also having a link=control field having an indication (A-bit) that a data frame is to be sent;

receiving said transmitted message command frame at said second location;

starting a message processor at said second location;

after said step of transmitting said message command frame, transmitting from said first location at least one data frame having an information field containing data for transmission to said second location, said message command frame having included an indication (A-bit) in said link-control field that said data frame was to be sent;

receiving said at least one data frame at said second location, the transmission of said data frame having been indicated by said A-bit in said message command frame;

determining whether an error has occurred in said information field of said at least one data frame;

providing a quiesce indication to said message processor upon the condition that an error has occurred in said information field of said at least one data frame;

discarding said at least one received data frame upon the determination that an error is present in said information field of said at least one data frame and replying to said first location by transmitting thereto a frame indicating that an error has occurred in said at least one received data frame; and

notifying said originator of the resulting message status.

5. A method for direct transmission of frames between an originator at a first location and a recipient at a second location, said frames having at least a link-control field, said method for transmitting comprising the steps of:

transmitting from said first location a message command frame having an information field specifying a command;

receiving said transmitted message command frame at said second location;

starting a message processor at said second location;

transmitting from said second location to said first location a message response frame;

discarding said message response frame upon detection that an error is present in the information field of said message response frame; and

notifying said originator of resulting message response.

6. The method of claim 5 further including the steps of:

transmitting from said recipient to said originator, a data frame after said message processor is started, and

receiving at said first location an error-free data frame.

7. A method for direct transmission of frames between an originator at a first location and a recipient at a second location, said frames having at least a link-control field, said method for transmitting comprising the steps of:

transmitting from said first location a message command frame having an information field specifying a command;

receiving said transmitted message command frame at said second location;

starting a message processor at said second location;

transmitting from said recipient to said originator a data frame after said message processor is started;

receiving said data frame at said first location;

discarding said data frame upon detection of an error therein;

transmitting a message response frame from said second location to said first location; and

receiving said message response frame at said first location notifying said originator of resulting message status.

8. The method of claim 7 in which said discarding step occurs as a result of an error is the information field of said data frame.

9. The method of claim 7 in which said discarding step occurs as a result of an error in the link-control field of said data frame and in which said message response frame includes an indication in the link-control field of said message response frame that a data frame had been previously sent from said second location.

10. A method for direct transmission of frames between an originator at a first location and a recipient at a second location, said frames having at least a link-control field, said method for transmitting comprising the steps of:

transmitting from said first location a message command frame having an information field specifying a command;

receiving said transmitted message command frame at said second location;

starting a message processor at said second location;

transmitting a data frame from said second location to said first location, said data frame containing a link-control field which includes an indication (A-bit) that more data is to be sent;

receiving said transmitted data frame said second location at said first location;

discarding said data frame upon determination that an error is present in an information field of said data frame;

transmitting to said second location a frame directing said message processor to quiesce;

transmitting from said second location a frame indicating that said message processor was quiesced; and

notifying said originator of the resulting message response.