公开(公告)号：DE3069762D1

公开(公告)日：1985-01-17

申请号：DE3069762

申请日：1980-08-26

Applicant: IBM

Inventor： DONNAN ROBERT ANDERSON

IPC: G06F11/14 ,  H04L1/16 ,  H04L1/18 ,  H04L29/06

Abstract: A method and a system for the retransmission of incorrectly received frames in a transmission system in which information is transmitted in the form of sequentially numbered frames. Each information frame includes a so-called send sequence number, N(S), a bit, R, indicating if this information frame has previously been retransmitted, and an information field containing the information to be transmitted. At the transmitting station, a variable, V(T), whose value indicates the order in which a frame is retransmitted relative to the sequence of frames transmitted for the first time, is associated with each retransmitted frame. At the receiving station, the incoming information frames are checked for errors and the N(S) of frames found to be incorrect is noted. The receiving station then sends to the transmitting station a so-called Checkpoint (CP) message containing a so-called receive sequence number, N(R), which indicates the send sequence number, N(S), of the most recently received, non-retransmitted, error-free information frame, and, if at least one incorrect frame has been received, at least one identifier, N(X), which indicates the N(S) of the incorrect frame whose retransmission is requested. Upon receipt of the Checkpoint message, the transmitting station retransmits requested information frames that have not been previously retransmitted; it also retransmits previously retransmitted frames, only if the V(T) values associated therewith are less than the receive sequence number, N(R), contained in the CP message; and it updates the V(T) value associated with each frame thus retransmitted. In a preferred embodiment of the invention, the Checkpoint messages are transmitted on a periodic basis. Each of these contains an X bit whose value indicates whether the values between N(R) and the highest N(X) are also to be considered as N(X) values.

公开(公告)号：DE2301727A1

公开(公告)日：1973-08-23

申请号：DE2301727

申请日：1973-01-13

Applicant: IBM

Inventor： BOUDREAU PAUL EMIL ,  DIXON ROY CONRAD ,  DONNAN ROBERT ANDERSON ,  MOSS EUAL AARON

IPC: H04L5/22 ,  G06F13/00 ,  G06F13/42 ,  H04L12/433 ,  G06F3/04

Abstract: A serial loop data communications system having store and forward capability at each terminal interface on the loop and in which data signal entities, each of which includes a plurality of data bits, addressed to subsequent terminals on the loop are stored in successive locations in a serial storage device when received if a terminal associated with the interface is transmitting. At the termination of data transmission by the associated terminal, the previously stored data signal entities are forwarded from the data entity storage position occupied by the oldest received entity and subsequently received entities are advanced to successive entity storage positions until data signal entities for subsequent terminals on the loop are no longer received, at which time advancement of the data signal entities is terminated and the data signal entities then remaining in storage, are forwarded from the successive entity storage locations in the serial storage in the order of receipt.

公开(公告)号：DE2447255A1

公开(公告)日：1975-06-12

申请号：DE2447255

申请日：1974-10-03

Applicant: IBM

Inventor： BOUDREAU PAUL EMILE ,  BRODD WYNENE DONALD ,  DONNAN ROBERT ANDERSON

IPC: H03M13/00 ,  G06F11/10 ,  H03M7/40 ,  H03M13/03 ,  H04L1/00 ,  H04L1/10

Abstract: In the transmission of variable length frames of digital information separated by one or more flag sequences, a block check is generated and appended to the information bits at the transmitter. The block check is generated by Exclusive OR'ing a predetermined non-zero number to the high order information bits and generating (n-k) check digits according to a cyclic error detecting code. The (n-k) check digits are Exclusive OR'd with an (n-k) bit non-zero number to produce the block check. At the receiver, the first mentioned non-zero number is added to the high order information bits and an (n-k) digit number is generated according to the same cyclic error detecting code used at the transmitter. This number is checked to see if it conforms to a predetermined number indicating error-free transmission. Utilizing the above approach, transmission errors in or near the flag sequence are detected, as well as those which may occur in the information field.

公开(公告)号：DE1034661B

公开(公告)日：1958-07-24

申请号：DEI0012595

申请日：1956-12-20

Applicant: IBM DEUTSCHLAND

Inventor： TOEPPEN THURSTON HOMER ,  DONNAN ROBERT ANDERSON

IPC: B41J19/02 ,  B41J19/42 ,  B41J19/62