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CN-122027578-A - Point brake type flow control method

CN122027578ACN 122027578 ACN122027578 ACN 122027578ACN-122027578-A

Abstract

The invention provides a point brake type flow control method, which comprises a point brake type flow control method based on a port level and a priority queue, wherein the fine control on a lossless queue is realized by comparing the depth of a total buffer queue at the current moment and judging whether to execute point brake according to the relation between the total in-transit data and the buffer space which are about to be reached in the pre-estimated 2T time of stored flight information. Under the condition that the bandwidth and the equipment distance are kept unchanged, the point brake type flow control method provided by the invention has the advantages that the occupied cache space is relatively smaller than that of the traditional PFC, and the occupation of half of the cache space can be nearly reduced under the condition that the point brake frequency is high. Therefore, under the condition that the size of the buffer memory space and the bandwidth are fixed, the point brake type flow control method can support a long-distance lossless scene with a longer distance than the traditional PFC.

Inventors

  • PAN WENTAO
  • WANG BIN

Assignees

  • 南京邮电大学

Dates

Publication Date
20260512
Application Date
20260210

Claims (5)

  1. 1. The port-level-based point brake type flow control method is characterized by comprising the following steps of: s1, judging whether the time of the spot brake is reached, and executing subsequent judgment only at the time point when the spot brake can be sent; S2, inquiring the total cache queue depth B of the port at the current moment, and predicting the total amount A of in-transit data to be achieved in 2T abs time according to stored flight information, wherein T abs is one-way forwarding time delay between two end devices; s3, respectively comparing the total buffer queue depth B with a preset threshold value threshold and the total data amount in transit A+the relation between the total buffer queue depth B and BDP, wherein BDP=B abs *2T abs ,B abs is port bandwidth; S4, when B is more than or equal to threshold and A+B is more than BDP, executing point brake, wherein the point brake time is t, and when t time passes, restoring flow transmission and re-executing S1, and realizing fine control on the lossless queue in a cyclic reciprocation mode.
  2. 2. The point brake type flow control method based on the priority queue is characterized by comprising the following steps: s1, judging whether the time of the spot brake is reached, and executing subsequent judgment only at the time point when the spot brake can be sent; S2, inquiring the total buffer queue depth B of the priority queue at the current moment, and predicting the total amount A of in-transit data to be achieved in 2T abs time according to stored flight information, wherein T abs is one-way forwarding time delay between two end devices; S3, inquiring the current total cache queue depth C of the whole port associated with the priority queue at the current moment, and predicting the total amount D of in-transit data to be reached in 2T abs time according to stored flight information; S4, respectively comparing the total buffer queue depth B with a preset threshold value threshold and the total data amount in transit A+the relation between the total buffer queue depth B and BDP, wherein BDP=B abs *2T abs ,B abs is port bandwidth; s5, judging a port level point brake result according to the associated integral port, and judging the port level point brake when C+D > beta is BDP, otherwise judging the point brake result of the priority queue, wherein when beta is minimum to be 1, allowing overdriving; S6, when B is more than or equal to threshold and A+B is more than BDP, executing point brake, wherein the point brake time is t, and when t time passes, restoring flow transmission and re-executing S1, and realizing fine control on the lossless queue in a cyclic reciprocating manner.
  3. 3. The method according to any one of claims 1 or 2, wherein the preset threshold is set to 0 to achieve minimum buffering.
  4. 4. The method according to any one of claims 1 or 2, wherein the point-brake time T is a minimum value to achieve that the buffer queue depth B and the upcoming traffic a within 2T abs time remain always around one BDP.
  5. 5. The method for controlling the flow according to any one of claims 1 and 2, wherein the simultaneous judgment of the point brake results of the plurality of groups of ports is realized by means of a serial pipeline.

Description

Point brake type flow control method Technical Field The invention relates to the technical field of communication, in particular to a point brake type flow control method based on port level and priority queue. Background Priority-based flow control adds a priority concept to the traditional flow control technology, can distinguish flows with different priority services, and can realize the requirement of guaranteeing high-priority service flows, is a point-to-point protocol, divides one Ethernet link into a plurality of virtual channels (8 at most), and distributes different priorities (0-7 levels) for each channel. When the network is congested, the system pauses the traffic of the current priority (pg) through a back pressure signal, other priorities can continue to transmit, and the total amount of low-priority transmission data is reduced to ensure that the key service has no packet loss. Conventional Priority Flow Control (PFC) controls the upstream device to stop sending traffic as shown in fig. 1, B pfc represents the interface bandwidth, and T pfc represents the unidirectional forwarding delay between device a and device B. And when the lossless queue buffer occupation of the equipment A is smaller than the back pressure frame triggering threshold, the equipment B continuously transmits the flow to the equipment A, and the lossless queue buffer occupation of the equipment A is gradually increased. And when the lossless queue buffer occupancy of the device A exceeds the back pressure frame triggering threshold, the device A sends the PFC back pressure frame to the device B to inform the device B to stop sending the traffic. During the time T pfc when the PFC backpressure frame does not reach device B, device B is still sending traffic to device a, and the lossless queue buffer occupancy of device a continues to increase. And the device B receives the PFC back-pressure frame sent by the device A and stops sending the traffic to the device A. When the device B stops sending traffic to the device a, the message sent by the device B before stopping the traffic is still sent to the device a, and the time T pfc needs to elapse before the message reaches the device a, and the lossless queue cache occupancy of the device a continues to increase in the time T pfc. The device A stops receiving the traffic sent by the device B, the lossless queue buffer occupancy of the device A reaches the maximum, and the device A starts to gradually decrease. In this process, in order to ensure that no packet loss occurs in the lossless queue, the buffer space of the lossless queue of the device a needs to continuously absorb the traffic B pfc*2Tpfc received in 2T pfc after exceeding the back pressure frame trigger threshold. The conventional process of retransmitting traffic after the upstream device is stopped under priority traffic control (PFC) is shown in fig. 2, when the lossless queue buffer occupancy of the device a is smaller than the back pressure frame stop threshold, the device a transmits a PFC back pressure frame to the device B to notify the device B that the device B starts transmitting traffic, after T pfc time, the device B receives the PFC back pressure frame transmitted by the device a and starts transmitting traffic to the device a, and the traffic transmitted by the device B to the device a needs to pass T pfc time before reaching the device a. Similarly, to ensure that the lossless queue does not lack throughput, the buffer space occupation of the lossless queue of the device a needs to be always greater than 0 in a period of 2T pfc after the back pressure frame stop threshold, so that the back pressure frame stop threshold is at least B pfc*2Tpfc. According to the analysis of the traditional priority flow control mechanism, the buffer space occupation needs at least 2*B pfc*2Tpfc, and if an optimized flow control method can be provided to reduce the buffer space occupation, a longer-distance lossless scene can be supported. Disclosure of Invention In order to solve the problems, the invention provides a point brake type flow control method which has the characteristics of short period, high frequency and continuous small amount of control flow transmission and suspension, so that the point brake type flow control is relatively less than the traditional PFC (power factor correction) which can occupy a buffer space under the condition that the bandwidth and the equipment distance are kept unchanged, and the occupation of the buffer space can be nearly reduced by half under the condition that the point brake frequency is high. The technical scheme provided by the invention is as follows: in a first aspect, a method for controlling a point brake type flow based on a port level includes the steps of: s1, judging whether the time of the spot brake is reached, and executing subsequent judgment only at the time point when the spot brake can be sent; S2, inquiring the total cache queue depth B of the port at