Smart aging retry buffer
A method and controller for sending data frames over a lossy bidirectional link between integrated circuit chips is disclosed. Upon transmission, frames are stored in a buffer. The detection of errors is indicated and triggers retransmission of the erroneously received frame, but acknowledgement of correctly received frames is not indicated. Instead, the sending controller assumes that frames were correctly received if no error indication is received after a period of time. The period of time is the maximum amount of time that would be taken for the sending controller to receive an error indication if the frame was received with an error. After said period of time, the sent frame is discarded from the buffer.
1. A method of sending a frame of data on a link, comprising:
storing the frame in a buffer coupled to a transmitter;
transmitting, by the transmitter, the frame over the link;
in response to receiving an input indicating that an error has occurred in the transmission of the frame, retransmitting the frame from the buffer;
monitoring a state of a receive channel of the link;
in response to not receiving the input upon or after a maximum round trip duration between a time of the transmission and a time the input would be received, discarding the frame from the buffer, wherein discarding the frame comprises:
scheduling a time before discarding the frame when the input can no longer be received for these frames based on the state of the receive channel.
2. The method of claim 1 , wherein the link is a bidirectional link and the input is received from the bidirectional link.
3. The method of claim 2 , further comprising:
performing error detection on a frame received from the bidirectional link; and
retransmitting at least the frame from the buffer if an error is detected in the received frame.
4. The method of claim 1 , where the duration of time corresponding to the state of the link is the maximum round trip duration.
5. The method of claim 1 , wherein the buffer stores fewer than a number of frames that could be sent in the maximum round trip duration.
6. The method of claim 1 wherein the link can be in a power saving state.
7. A controller for sending frames of data on a link, comprising:
a buffer, coupled to a transmitter, configured for storing one or more frames;
an input device configured to receive an indication of whether an error has occurred; and
wherein the transmitter is configured for transmitting a frame of the one or more frames and, responsive to the input device receiving the indication indicating that the error has occurred, configured for retransmitting the frame from the buffer, and, responsive to the input device not receiving the indication upon or after a maximum round trip duration between a time of the transmission and a time the input would be received, configured for discarding the frame from the buffer; and wherein the controller monitors a state of a receive channel of the link and schedules a time before discarding the frame when the input can no longer be received for these frames based on the state of the receive channel.
8. The controller of claim 7 , further comprising a receiver, and wherein the link is a bidirectional link coupled to the receiver.
9. The controller of claim 8 , further comprising:
an error detection unit that accepts a frame received from the bidirectional link and triggers a retransmit of the one or more frames from the buffer upon the indication that an error is detected in the received frame.
10. The controller of claim 8 , wherein a size of the buffer is less than a number of frames that could be sent in the maximum round trip duration.
11. The controller of claim 8 , wherein the link can be in a power saving state.