Limited automatic repeat request protocol for frame-based communication channels
First Claim
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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Accused Products
Abstract
In a frame-switched network, a sender sends frames to a receiver over a possibly unreliable channel. Sent frames include frame identifiers that can be used for a limited automatic repeat request. Upon receipt of a frame, the receiver determines, from the frame identifier, if frames prior to the received frame were lost in transit. If the receiver determines that it missed a prior frame, the receiver sends the sender a negative acknowledgment (nack) for the missed prior frame or frames. Otherwise, if the receiver receives a frame correctly, it does not acknowledge the frame. The frame identifiers can be a set of sequential integers with frames transmitted in sequential frame order. In some embodiments, when a receiver receives a frame out of order, the receiver buffers the out of order frame in a receiver buffer for a receive buffer period until preceding frames are received or a receive buffer period expires. The sender can send a reminder frame to the receiver to allow the receiver to detect a missed prior frame missing from an end of a frame sequence. The channel between the sender and the receiver can be a bidirectional channel over a telephone wire, a cable, a radio frequency link or a power wire. Multiple logical channels might be set up between a given sender-receiver pair, to allow for traffic of varying priorities.
116 Citations
3 Claims
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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:
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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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2. 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:
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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) from the receiver to the sender, the nack including an indication of the missed prior frame the indication of the missed prior frame including a frame identifier of a first missed frame and a number of sequential missed frames following the first missed 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; 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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3. 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:
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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 for a buffer period and tracking the buffer period for each frame;
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) 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; 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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Specification