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    METHOD AND SYSTEM FOR RETRANSMITTING INCORRECTLY RECEIVED NUMBERED FRAMES IN A DATA TRANSMISSION SYSTEM
    4.
    发明专利
    METHOD AND SYSTEM FOR RETRANSMITTING INCORRECTLY RECEIVED NUMBERED FRAMES IN A DATA TRANSMISSION SYSTEM 未知

    公开(公告)号：CA1155521A

    公开(公告)日：1983-10-18

    申请号：CA381273

    申请日：1981-07-07

    Applicant: IBM

    Inventor： DONNAN ROBERT A

    IPC: G06F11/14 ,  H04L1/16 ,  H04L1/18 ,  H04L29/06 ,  H04L1/00

    Abstract: METHOD AND SYSTEM FOR RETRANSMITTING INCORRECTLY RECEIVED NUMBERED FRAMES IN A DATA TRANSMISSION SYSTEM 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 is representative of the order in which a frame is re-transmitted 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), representative of the send sequence number, N(S), of the most recently received, non-retransmitted, errorfree information frame, and, if at least one incorrect frame has been received, at least one identifier, N(X), representative of 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.

    ERROR CONTROL SYSTEM
    5.
    发明专利
    ERROR CONTROL SYSTEM 未知

    公开(公告)号：CA1017867A

    公开(公告)日：1977-09-20

    申请号：CA212863

    申请日：1974-11-01

    Applicant: IBM

    Inventor： BOUDREAU PAUL E ,  BRODD WAYNE D ,  DONNAN ROBERT A

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

    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.

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