Time-sensitive network traffic scheduling method based on idle guard band

Abstract

The invention relates to a time-sensitive network traffic scheduling method based on an idle guard band, and belongs to the technical field of traffic transmission. A guard band mechanism in a time-sensitive network mainly provides service for a TT stream, so that the transmission delay of an AVB stream is large and even exceeds the deadline; and the transmission time of most TSN streams may be far less than the maximum transmission time unit, so that no traffic transmission in a certain period of time forms an idle guard band, resulting in waste of bandwidth. According to the method, AVB flow transmission is optimized by considering the AVB flow and the deadline of the AVB flow, the AVB flow is transmitted in the idle guard band period, the priority of the AVB flow is redefined according to the deadline of the AVB flow, and the guard band is filled with the AVB flow which is cut off at the earliest for transmission. The method not only ensures the transmission delay and stability of the TT flow, but also improves the transmission success rate of the AVB flow and the bandwidth utilization rate of the whole transmission link.

Description

Technical Field

[0001] The invention belongs to the technical field of traffic transmission, and relates to a time-sensitive network traffic scheduling method based on an idle protection band. Background Art

[0002] With the rapid development of key fields such as aerospace, automotive industry and industrial automation, these time-sensitive systems have generated massive amounts of network data, which has put forward more stringent requirements on the bandwidth and latency of communication networks. However, traditional Ethernet communication adopts a "best effort" data transmission mode. In this way, the data packets in the network lack priority distinction, making it difficult to ensure the high real-time and high reliability of data packet transmission in time-sensitive network systems. Based on traditional Ethernet, the IEEE802.1 working group has developed a time-sensitive network (TSN), which can ensure the transmission of time-sensitive traffic with high reliability and stability. In a time-sensitive network, there are three types of traffic with different real-time requirements: time-triggered (TT) traffic with the highest priority, which is transmitted in a periodic manner and has extremely strict requirements on latency and stability. Any delay in TT traffic transmission may cause unpredictable damage to the system; audio and video (AVB) traffic with medium priority, which has relatively loose real-time requirements on latency and stability, allowing transmission delays within a certain range, but the stable transmission of AVB traffic should still be ensured as much as possible; best effort (BE) traffic with the lowest priority, which is transmitted when network resources are idle and has relatively low requirements on transmission latency and stability.

[0003] In the traditional Ethernet transmission mode, the non-preemptive transmission mechanism is adopted, which means that once the data traffic starts to be transmitted, it cannot be interrupted and the next traffic can only be transmitted after the current traffic is transmitted. This mechanism may cause the TT traffic to suffer unexpected delays when the high-priority TT traffic arrives, if the AVB or BE traffic has not been transmitted, which will cause system failure. In order to ensure the deterministic transmission of TT traffic, the time-sensitive network technology introduces the IEEE802.1Qbv and IEEE 802.1Qbu protocols, which correspond to non-preemptive transmission and preemptive transmission respectively. In the non-preemptive transmission mode, the time-sensitive network uses the guard band mechanism to close the transmission gates of other queues in advance, and control the next frame to be processed to stop transmission before the TT traffic is transmitted, thereby ensuring the deterministic transmission of TT traffic. In the non-preemptive traffic transmission process, IEEE802.1Qbv recommends the use of fixed and variable guard bands, where the size of the variable guard band depends on the size of the queued frame to ensure that the non-TT traffic is transmitted before the TT traffic is transmitted. Although variable guard bands can save bandwidth and improve the schedulability of AVB traffic to a certain extent, it becomes difficult to achieve transmission when the amount of data is huge. This is because the non-preemptive mode requires accurate acquisition of detailed information on the AVB and BE traffic to be transmitted, such as traffic size, occurrence time, and priority, which will significantly increase the complexity of system design and the execution time of the scheduling algorithm. At the same time, due to factors such as scheduling methods and shaping mechanisms, the size of non-TT traffic is difficult to determine in advance. Therefore, in most cases, a fixed guard band mechanism is used to ensure the stability of TT stream transmission. Summary of the invention

[0004] Although the introduction of the guard band mechanism in the time-sensitive network ensures the deterministic transmission of TT flows, it also brings the following negative effects: (1) The guard band mechanism mainly provides services for TT flows, but fails to fully consider the transmission requirements of AVB flows, resulting in a large transmission delay of AVB flows, even exceeding the deadline. (2) In order to ensure the deterministic transmission of TT flows, the size of the guard band is usually set to the maximum transmission time unit of the time-sensitive network transmission flow. In actual applications, the transmission time of many TSN flows may be much smaller than the maximum transmission time unit, resulting in no traffic transmission for a certain period of time, forming an idle guard band, which further leads to bandwidth waste.

[0005] In view of this, the purpose of the present invention is to provide a time-sensitive network traffic scheduling method based on an idle protection band. The present invention provides a technical solution, comprising the following steps:

[0006] S1. Calculate the idle protection band. The specific process is as follows:

[0007] S11. Calculate the size of the idle protection band in GB size :

[0008] GB size =max{F TRT},F∈F TSN

[0009] Among them, F TSN represents time-sensitive network traffic, F TRT Represents the transmission time of all time-sensitive network traffic to be transmitted;

[0010] S12. Calculate the start time GB of the idle protection band start :

[0011]

[0012] in, Represents the periodic arrival time of time-triggered (TT) traffic;

[0013] S13. Calculate the bandwidth of the i-th idle guard band as follows:

[0014] If the end time of the last transmission flow of the i-th transmission cycle is Greater than or equal to the start time of the idle protection band but:

[0015]

[0016] like Less than but:

[0017]

[0018] Among them, among them, Indicates when the next transmission cycle of the i-th TT traffic arrives;

[0019] S2. Determine the AVB (Audio Video Bridging) traffic transmission constraints. The specific process is as follows:

[0020] S21. Determine that the current AVB traffic queue transmission gate is open;

[0021] S22. Determine the credit value of the current AVB traffic Greater than or equal to zero;

[0022] S23. AVB traffic queue to be transmitted during the idle guard band is not null;

[0023] S3. Determine the AVB traffic that should be transmitted currently. The specific process is as follows:

[0024] S31. AVB traffic that should be transmitted currently The deadline of the AVB traffic should be earlier than the deadline of all AVB traffic to be transmitted.

[0025]

[0026] in, represents the deadline of the i-th AVB traffic to be transmitted;

[0027] S32. AVB traffic that should be transmitted currently The arrival time of the AVB traffic should also be earlier than the arrival time of all AVB traffic to be transmitted.

[0028]

[0029] in, represents the arrival time of the i-th AVB traffic to be transmitted;

[0030] S4. Perform traffic transmission. The specific process is as follows:

[0031] S41. Calculate the AVB traffic set to be transmitted through the above S1 to S3

[0032]

[0033] S42. Transmit the AVB traffic in the idle protection band according to the sequence of the AVB traffic set to be transmitted, and ensure that the last AVB traffic to be transmitted The deadline is less than or equal to the idle protection band GB surplus The deadlines are as follows:

[0034]

[0035] The beneficial effects of the present invention are:

[0036] By comprehensively considering AVB traffic and its deadline, AVB traffic transmission is optimized. During the idle protection band, AVB streams are transmitted and their priorities are redefined according to the deadline of AVB traffic. The earliest AVB traffic that is cut off is filled into the protection band for transmission, ensuring that AVB traffic can be transmitted before the deadline as much as possible, thereby reducing the risk of data loss. This strategy improves the transmission success rate of AVB traffic and the bandwidth utilization of the entire transmission link while ensuring the transmission delay and stability of TT traffic.

[0037] Other advantages of the present invention. The objects and features will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objects and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0039] Figure 1 Transmitting schematics for time-sensitive network traffic;

[0040] Figure 2 This is a schematic diagram of the guard band mechanism for time-sensitive networks;

[0041] Figure 3 This is an idle guard band traffic transmission flow chart of the time-sensitive network traffic scheduling method based on the idle guard band proposed by the present invention. DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0043] The accompanying drawings are only used for illustrative purposes and are schematic diagrams rather than actual drawings, and should not be construed as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted. They may be enlarged or reduced, and do not represent the size of actual products. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0044] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back" and the like indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction. It is constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0045] The present invention mainly focuses on the transmission of TT traffic and AVB traffic in time-sensitive networks. m It is expressed as the following formula:

[0046] F m = {P m ,TD m ,AT m ,D m}

[0047] Among them, m represents the mth flow to be transmitted, P represents the transmission period of the current flow, TD represents the transmission duration of the current flow, AT represents the time when the current flow arrives at the transmission queue, and D represents the deadline of the current flow.

[0048] If the current network traffic is schedulable, the difference between the traffic sending time ST and the time AT when the traffic arrives at the transmission queue plus the traffic transmission duration TD must not exceed the traffic deadline D. Therefore, the traffic transmission constraint formula is expressed as follows:

[0049] ST-AT+TD≤D

[0050] See also Figure 1 , which is a schematic diagram of the time-sensitive network traffic transmission principle. In a time-sensitive network transmission system, a time-aware shaper is usually used to transmit traffic. The time-aware shaper is an enhanced function defined by IEEE 802.1Qbv for planned traffic transmission. Figure 1The forwarding process of time-sensitive network traffic is demonstrated: first, after the traffic enters the ingress port from the input 1 and input 2 ends of the input end, the forwarding route is determined by the switch engine and enters the priority filter; then, the priority filter will distribute the network traffic to the corresponding priority queue (Queue) according to the priority information carried by each time-sensitive network traffic; then the time-aware shaper controls the queue transmission gate (Gate) to open and close periodically according to the gate control list (GCL), and allocates corresponding transmission time slices to each transmission queue (Queue).

[0051] For the transmission of AVB streams, the time-sensitive network uses a credit-based shaper (CBS) to control the transmission of AVB traffic. Specifically, the transmission of AVB streams must meet the following conditions before the AVB traffic is transmitted:

[0052] 1. The transmission gate of the AVB queue is open;

[0053] 2. The credit value of the AVB stream is greater than or equal to zero at the beginning of the transmission;

[0054] 3. There is no traffic with a higher priority than AVB traffic to be transmitted in the current transmission time slice.

[0055] CBS controls the change of the credit value of AVB traffic according to the bandwidth. The main parameters of CBS include idle slope (IdleSlope) and send slope (SendSlope). The credit value change of the current traffic is controlled based on these two parameters. The relationship between the idle slope of AVB traffic and the send slope of AVB traffic is specifically expressed as the following formula:

[0056] IdleSlope AVB +SendSlope AVB ≤MTR

[0057] Among them, IdleSlope AVB Represents the idle slope of AVB traffic, SendSlope AVB It represents the sending slope of AVB traffic, and MTR represents the maximum traffic transmission rate. IdleSlope and SendSlope change continuously with the transmission of AVB traffic.

[0058] See also Figure 2 , which is the principle diagram of the guard band mechanism of time-sensitive network. Figure 2Taking the packet containing two transmission cycles as an example, each transmission cycle transmits traffic of different priority levels. Priority 4 represents the transmission time slice allocated to TT traffic; other priorities represent the transmission time slices allocated to other time-sensitive network traffic; the guard band (GB) is a bandwidth before the boundary of each TT flow transmission cycle. The guard band represents an idle transmission time slice, which is used to ensure that the current transmission cycle will not affect a cycle, thereby ensuring the deterministic transmission of the TT flow.

[0059] The time-sensitive network traffic scheduling method based on idle protection band proposed in the present invention mainly comprises the following steps:

[0060] S1. Calculate the idle guard band:

[0061] In order to ensure the deterministic transmission of TT streams, the size of the guard band is GB. size It is usually set to the maximum transmission time of all streams to be transmitted, which is specifically expressed as the following formula:

[0062] GB size =max{F TRT},F∈F TSN

[0063] where F TSN represents time-sensitive network traffic, F TRT Represents the transmission time of all time-sensitive network traffic to be transmitted. Because the transmission of TT is periodic, the start time of the idle protection band GB start It is expressed as the following formula:

[0064]

[0065] in represents the periodic arrival time of the TT flow, GB size Represents the size of the guard band.

[0066] If the idle guard band is used for AVB traffic transmission, there may still be unfinished traffic before the guard band starts. unfinished The start transmission time of this part of traffic is in GB start Therefore, it is necessary to wait until such traffic is transmitted before transmitting AVB traffic during the protection band. At the same time, the difference between the end time of the current period's protection band and the end time of the untransmitted traffic is recorded as the idle protection band, and the specific available bandwidth for AVB traffic transmission is obtained. If the end time of the last transmission traffic of the i-th transmission cycle is greater than or equal to the start time of the idle protection band, then the i-th idle protection band bandwidth It is expressed as the following formula:

[0067]

[0068] in represents the arrival time of the next transmission cycle of the i-th TT stream, Indicates the end time of the last flow in the i-th transmission period.

[0069] If the end time of the last transmission flow of the i-th transmission cycle is less than the start time of the idle guard band, the i-th idle guard band bandwidth It is expressed as the following formula:

[0070]

[0071] S2. Determine AVB traffic transmission constraints:

[0072] AVB traffic transmission selection is subject to CBS constraints and needs to meet the following two conditions at the same time:

[0073] 1. The current AVB queue transmission gate is open;

[0074] 2. The credit value of the current AVB traffic is greater than or equal to zero.

[0075] During the idle guard band setting, the AVB queue transmission gate must be kept open. The AVB traffic selection conditions during the idle guard band transmission are as follows:

[0076] 1. The currently selected AVB traffic credit value is non-negative and is expressed as follows:

[0077]

[0078] in It is calculated and constrained by the idle slope and the sending slope that control the change of the credit value of the current flow.

[0079] 2. During the idle guard band, there is AVB traffic to be transmitted, that is, the AVB queue is not empty, which is expressed as the following formula:

[0080]

[0081] in Represents an AVB traffic set.

[0082] S3. Determine the AVB traffic that should be transmitted currently:

[0083] The present invention aims to ensure that the success rate is maximized when transmitting AVB traffic and improve the bandwidth utilization of the overall transmission link. Therefore, the transmission must be completed as much as possible before the deadline of the AVB traffic. When determining the AVB traffic that should be transmitted currently, two key constraints must be followed:

[0084] 1. AVB traffic that should be transmitted The deadline of is the earliest among all AVB traffic to be transmitted, expressed as the following formula:

[0085]

[0086] in, Represents the deadline for the i-th AVB traffic to be transmitted.

[0087] 2. Under the above constraints, when the AVB traffic to be transmitted with the same deadline is screened out by the formula, it should be ensured that the AVB traffic to be transmitted has the earliest arrival time, which is expressed as the following formula:

[0088]

[0089] in Represents the arrival time of the i-th AVB traffic to be transmitted.

[0090] S4. Perform traffic transmission:

[0091] Through the above S1~S3, we can calculate a set of AVB traffic that should be transmitted Subsequently, during the idle guard band, the AVB traffic is transmitted according to the traffic set, which is expressed as follows:

[0092]

[0093] In the idle protection band, the AVB traffic is transmitted in the order of the AVB traffic set to be transmitted. At the same time, during the transmission of the traffic, the AVB traffic set to be transmitted is also continuously updated to ensure that the last AVB traffic to be transmitted is transmitted. The deadline is less than or equal to the idle protection band GB surplus , expressed as the following formula:

[0094]

[0095] According to S1 to S4 above, the AVB traffic of the current cycle is transmitted in the idle guard band. If new AVB traffic arrives at the head of the transmission queue during the idle guard band, S3 and S4 are repeated to continuously update the AVB traffic set to be transmitted to ensure that the AVB traffic can be transmitted before the deadline, until the idle guard band can no longer transmit AVB traffic.

[0096] The present invention aims to solve the adverse effect of the guard band mechanism introduced to ensure the deterministic transmission of TT traffic in a time-sensitive network on AVB traffic. To this end, a time-sensitive network traffic scheduling method based on idle guard band is proposed.

[0097] See also Figure 3 , the present invention proposes a flow chart of idle guard band traffic transmission based on the time-sensitive network traffic scheduling method of idle guard band. After the traffic enters the time-sensitive network transmission system, according to Figure 1 The gate control list shown in the figure opens and closes the transmission queue gate periodically. In a transmission cycle, when all traffic before the protection band is transmitted, the AVB traffic transmission queue gate will be opened to transmit the traffic in the current AVB queue. The specific steps are as follows:

[0098] Step 1. Determine the traffic transmission constraints. This is used to determine whether the current network traffic is schedulable. Ensure that the difference between the sending time and arrival time of the current traffic plus the sum of the transmission time of the current traffic is less than the deadline, indicating that the current traffic is in the effective transmission period.

[0099] Step 2. Calculate whether the current time has reached the start time of the idle guard band. If the end time of the last traffic transmitted before the guard band in the current transmission cycle is the start time of the idle guard band, the start time of the idle guard band is equal to the start time of the guard band. If the end time of the last traffic transmitted before the guard band in the current transmission cycle is after the guard band, the start time of the idle guard band is equal to the end time of the last traffic.

[0100] Step 3. Determine whether the idle guard band can transmit the minimum AVB traffic. Set the idle guard band size of the current transmission cycle and compare it with the minimum transmission time of the AVB traffic. If the idle guard band is smaller than the minimum transmission time of the AVB traffic, it means that the current idle guard band cannot transmit any AVB traffic and directly enters the next transmission cycle; if the idle guard band is larger than the minimum transmission time of the AVB traffic, it means that the current idle guard band can transmit at least one AVB traffic and enters step 4.

[0101] Step 4: Determine the AVB traffic transmission constraints, obtain the AVB traffic to be transmitted and the selected AVB traffic, and sort them, specifically:

[0102] When the current AVB queue transmission gate is open and the credit value of the current AVB traffic is greater than or equal to zero, if the credit value of the currently selected AVB traffic is non-negative and there is AVB traffic to be transmitted during the idle guard band, the AVB traffic to be transmitted is determined using the following method:

[0103] If it is determined that the deadline of the AVB stream selected for transmission is the earliest among all the AVB streams to be selected, and the arrival time of the AVB stream to be selected is the earliest, then the process goes to step 5.

[0104] Step 5. Transmit the first AVB traffic in the selected AVB traffic set, and repeatedly update the selected AVB traffic set. If the end time of the next traffic to be transmitted in the set exceeds the end time of the protection band, end the current transmission cycle and prepare for the next transmission cycle. Otherwise, repeat step 5.

[0105] The present invention aims to solve the problem of deterministic transmission of TT traffic in a time-sensitive network, especially the adverse effects that the guard band mechanism may have on AVB traffic. To this end, the present invention proposes a time-sensitive network traffic scheduling method based on an idle guard band. By reasonably utilizing the idle guard band in the network to effectively transmit the AVB traffic, it is ensured that the AVB traffic can successfully complete the transmission task before the specified deadline. In addition, the present invention also utilizes the idle bandwidth resources that were originally unused, thereby improving the bandwidth utilization of the entire transmission link, achieving optimal resource configuration and network performance improvement. During the idle guard band, the AVB stream is transmitted, and its priority is redefined according to the deadline of the AVB traffic. The earliest AVB traffic is filled into the guard band for transmission, ensuring that the AVB traffic can complete the transmission as much as possible before the deadline, thereby reducing the risk of data loss. Through this method, not only the deterministic transmission of TT traffic is guaranteed, but also the transmission requirements of AVB traffic are taken into account, and efficient coordination of different types of traffic in the time-sensitive network and optimal utilization of network resources are achieved.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A time-sensitive network traffic scheduling method based on idle protection band, characterized in that The following steps are involved: S1. Calculate the idle protection band. The specific process is as follows: S11. Calculate the size of the idle protection band in GB size : GB size =max{F TRT },F∈F TSN Among them, F TSN represents time-sensitive network traffic, F TRT Represents the transmission time of all time-sensitive network traffic to be transmitted; S12. Calculate the start time GB of the idle protection band start : in, Represents the periodic arrival time of time-triggered (TT) traffic; S13. Calculate the bandwidth of the i-th idle guard band as follows: If the end time of the last transmission flow of the i-th transmission cycle is Greater than or equal to the start time of the idle protection band but: like Less than but: Among them, among them, represents the arrival time of the next transmission cycle of the i-th TT flow; S2. Determine the AVB (Audio Video Bridging) traffic transmission constraints. The specific process is as follows: S21. Determine that the current AVB traffic queue transmission gate is open; S22. Determine the credit value of the current AVB traffic Greater than or equal to zero; S23. AVB traffic queue to be transmitted during the idle guard band is not null; S3. Determine the AVB traffic that should be transmitted currently. The specific process is as follows: S31. AVB traffic that should be transmitted currently The deadline of the AVB traffic should be earlier than the deadline of all AVB traffic to be transmitted. in, represents the deadline of the i-th AVB traffic to be transmitted; S32. AVB traffic that should be transmitted currently The arrival time of the AVB traffic should also be earlier than the arrival time of all AVB traffic to be transmitted. in, represents the arrival time of the i-th AVB traffic to be transmitted; S4. Perform traffic transmission. The specific process is as follows: S41. Calculate the AVB traffic set to be transmitted through the above S1 to S3 S42. Transmit the AVB traffic in the idle protection band according to the sequence of the AVB traffic set to be transmitted, and ensure that the last AVB traffic to be transmitted The deadline is less than or equal to the idle protection band GB surplus The deadlines are as follows:

2. The time-sensitive network traffic scheduling method based on idle protection band according to claim 1 is characterized in that: Before S1, a step of determining traffic transmission constraints is added to determine whether the current network traffic is schedulable, as follows: ST-AT+TD≤D Among them, ST represents the sending time of the current traffic, AT represents the time when the current traffic arrives at the transmission queue, TD represents the transmission duration of the current traffic, and D represents the deadline of the current traffic.

3. The time-sensitive network traffic scheduling method based on idle protection band according to claim 1 is characterized in that: Before S1, a step is added to determine that there is no constraint condition that the current transmission time slice does not have a to-be-transmitted traffic with a higher priority than the AVB traffic, so as to control the current traffic credit value, as follows: IdleSlope AVB +SendSlope AVB ≤MTR Among them, IdleSlope AVB Represents the idle slope of AVB traffic, SendSlope AVB It represents the sending slope of AVB traffic, and MTR represents the maximum traffic transmission rate.

4. The time-sensitive network traffic scheduling method based on idle guard band according to claim 1 is characterized in that: Repeating S3 and S4 to continuously update the AVB traffic set to be transmitted If the end time of a certain flow to be transmitted in the set exceeds the end time of the protection band, the current AVB flow transmission cycle is ended and preparations are made for the next transmission cycle.

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