Preemptive packet transmission
Disclosed herein is technology to reduce latency of frames through a network device supporting various priorities. In an implementation, a method comprises configuring one or more priorities with a preemptive right over other one or more of said plurality of priorities; receiving frames in a sequence, each of the frames having a frame priority comprising of one of said plurality of priorities; queuing the received frames in a predetermined order based on a frame arrival time and the frame priority; transmitting a current frame based on a current frame priority and current frame arrival time; stopping transmission of the current frame when a later frame in the sequence is received that has a later frame priority with preemptive right over the current frame priority; transmitting an invalid frame check sequence; transmitting the later frame; and restarting the transmission of the current frame after transmitting the later frame.
1. A method to reduce latency of frames transiting through a network device with a plurality of input and output ports supporting at least two frame priorities, the method comprising:
receiving a sequence of frames for transmission from one of the plurality of input ports for transmission at one of the output ports, wherein each of the frames is configured with an associated frame priority, wherein the associated frame priority of each of the frames specifies a preemptive right, a priority right or a no right over each of other frame priorities;
queuing each of the received frames in a predetermined order based on a frame arrival time and the associated frame priority;
selecting a first frame to transmit on the output port;
stopping transmission of the first frame in response to receiving a second frame with an associated frame priority specifying a preemptive right over the associated frame priority of the first frame;
transmitting an invalid frame check sequence within the first frame;
transmitting the second frame;
retransmitting the first frame after the transmission of the second frame is completed; and
deleting each of the received frames after transmitting the frame.
2. The method of claim 1 , wherein
retransmitting the first frame after transmitting the second frame
commences when there are no other frames queued transmission with an associated frame priority higher than the associated priority of the first frame.
3. The method of claim 1 , wherein transmitting the invalid frame check sequence comprises transmitting the invalid frame check sequence in response to detecting the second frame with an associated frame priority indicating the preemptive right.
4. The method of claim 1 , wherein, after stopping the transmission of the first frame, retaining the first frame in queue according to the predetermined order.
5. A network device comprising:
a network interface that receives frames in a first sequence, queues the frames according to a second sequence based on a configured frame priority and transmits frames in order of the second sequence, wherein each configured frame priority specifies a preemptive right, a priority right or a no right over each of other configured frame priorities;
a controller operatively coupled with the network interface to stop transmission of a first frame in the sequence in response to receiving a second frame in the sequence with a predetermined priority that has the preemptive right over the first frame priority, and said controller instructing the network interface to transmit an invalid frame check sequence within the first frame before transmitting the second frame prior to retransmitting the first frame when transmission of the second frame is completed, wherein the controller is further configured to instruct the network interface to delete each of the received frames after the frame is transmitted.
6. The network device of claim 5 , wherein the
controller starts the retransmission of the first frame after transmitting the second frame when there are no other frames queued for transmission configured with a frame priority that specifies a preemptive right over the frame priority associated with
the first frame.
7. The network device of claim 5 , wherein the controller instructs the network interface to transmit the invalid frame check sequence in response to detecting the second frame.
8. The network device of claim 5 , wherein the controller maintains the current frame in the queue until the current frame is completely retransmitted.
9. The network device of claim 8 , wherein the controller removes the current frame from the queue after it is completely retransmitted.