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Limited automatic repeat request protocol for frame-based communication channels

  • US 6,335,933 B1
  • Filed: 05/21/1999
  • Issued: 01/01/2002
  • Est. Priority Date: 05/21/1999
  • Status: Expired due to Fees
First Claim
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1. In a frame-switched network apparatus, a method of sending frames from a sender to a receiver over a possibly unreliable channel, the method comprising the steps of:

  • forming a frame at the sender, wherein the frame contains data to be transmitted to the receiver;

    including a frame identifier in the frame selected from a set of frame identifiers;

    retaining a copy of the frame at the sender;

    sending the frame from the sender to the receiver over the channel, independent of a presence of the receiver on the possibly unreliable channel;

    upon receipt of a frame at the receiver, identifying a frame identifier for the received frame;

    detecting, from the frame identifier, if a prior frame was missed;

    if a missed prior frame is detected in the step of detecting, sending a negative acknowledgment (nack) at least two times from the receiver to the sender, the nack including an indication of the missed prior frame;

    if a nack is received at the sender, determining the frame identifier of the missed prior frame and resending the missed prior frame if a copy of the missed prior frame is still retained at the sender;

    delaying a second nack from the receiver for a response period, wherein the response period is related to the time delay expected between sending the first nack and expected receipt of a retransmitted frame and is a dynamically determined time determined from measured frame travel times;

    . retransmitting the missed prior frame once for each nack received; and

    releasing, independent of an acknowledgment of a successful receipt of the transmitted frame by the receiver, the retained copy of the transmitted frame when a storage constraint is reached.

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