A Time-Sensitive Network Traffic Scheduling Method Based on Idle Guard Band

Abstract

This invention relates to a traffic scheduling method for time-sensitive networks (TSNs) based on an idle guard band, belonging to the field of traffic transmission technology. Because the guard band mechanism in TSNs primarily serves TT (Time-to-Traffic) flows, AVB (Asynchronous Passive Flow) flows experience significant transmission delays, sometimes exceeding their cutoff times. Furthermore, the transmission time of most TSN flows may be much shorter than the maximum transmission time unit, resulting in idle guard bands during certain periods of traffic transmission, leading to bandwidth waste. This invention optimizes AVB traffic transmission by considering AVB flow and its cutoff times. AVB flow is transmitted during the idle guard band, and its priority is redefined based on its cutoff time. The earliest-cutting AVB flow is then added to the guard band for transmission. This method ensures both the transmission delay and stability of TT flows while improving the transmission success rate of AVB flows and the overall bandwidth utilization of the transmission link.

Description

Technical Field

[0001] This invention belongs to the field of traffic transmission technology and relates to a time-sensitive network traffic scheduling method based on idle guard band. Background Technology

[0002] Against the backdrop of rapid development in key sectors such as aerospace, automotive, and industrial automation, these time-sensitive systems generate massive amounts of network data, placing increasingly stringent demands on the bandwidth and latency of communication networks. However, traditional Ethernet communication employs a "best-effort" data transmission model, which lacks prioritization of data packets, making it difficult to ensure high real-time performance and reliability in time-sensitive network systems. Building upon traditional Ethernet, the IEEE 802.1 working group developed Time-Sensitive Networking (TSN), a network that ensures high reliability and stability for the transmission of time-sensitive traffic. In time-sensitive networks, there are three types of traffic with different real-time requirements: Time-Triggered (TT) traffic, which has the highest priority, is transmitted periodically and has extremely strict requirements for latency and stability. Any delay in the transmission of TT traffic may cause unpredictable damage to the system; Audio-Video Bridging (AVB) traffic, which has relatively relaxed real-time requirements for latency and stability, allowing for transmission delays within a certain range, but still should ensure stable transmission of AVB traffic as much as possible; and Best-Effort (BE) traffic, which has the lowest priority, is transmitted when network resources are idle and has relatively low requirements for transmission latency and stability.

[0003] In traditional Ethernet transmission, a non-preemptive transmission mechanism means that once data traffic begins, it cannot be interrupted; the next traffic can only be transmitted after the current traffic has finished. This mechanism can lead to unexpected delays in high-priority TT traffic if AVB or BE traffic has not yet completed, potentially causing system failures. To ensure deterministic transmission of TT traffic, Time-Sensitive Networking (TSN) technology introduces the IEEE 802.1Qbv and IEEE 802.1Qbu protocols, corresponding to non-preemptive and preemptive transmission, respectively. In non-preemptive transmission mode, TSN uses a guard band mechanism to preemptively close the transmission gates of other queues, controlling the next frame to be processed to stop transmission before the TT traffic, thus ensuring deterministic transmission of TT traffic. During non-preemptive traffic transmission, IEEE 802.1Qbv recommends using fixed and variable guard bands, where the size of the variable guard band depends on the size of the queued frames to ensure that non-TT traffic completes transmission before the TT traffic. While variable guard bands can save bandwidth and improve the schedulability of AVB traffic to some extent, achieving transmission becomes difficult with large data volumes. This is because non-preemptive mode requires accurate acquisition of detailed information about the AVB and BE traffic to be transmitted, such as traffic size, occurrence time, and priority. This significantly increases the complexity of system design and the execution time of the scheduling algorithm. Furthermore, 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 Time-Sensitive Networking (TSN) ensures deterministic transmission of TT streams, it also brings the following negative impacts: (1) The guard band mechanism mainly serves TT streams but fails to fully consider the transmission needs of AVB streams, resulting in large transmission delays for AVB streams, even exceeding the deadline. (2) In order to ensure deterministic transmission of TT streams, the size of the guard band is usually set to the maximum transmission time unit of the time-sensitive network transmission stream. In practical applications, the transmission time of many TSN streams may be much smaller than the maximum transmission time unit, resulting in no traffic transmission during a certain period, forming an idle guard band, which further leads to a waste of bandwidth.

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

[0006] S1. Calculate the empty protection zone, the specific process is as follows:

[0007] S11. Calculate the size of the free guardrail (GB) size :

[0008] GB size =max{F TRT}, F∈F TSN

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

[0010] S12. Calculate the start time of the idle guard band (GB) start :

[0011]

[0012] in, This 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 traffic in 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, This indicates when the next transmission cycle of the i-th TT traffic arrives;

[0019] S2. Determine the audio / video bridging (AVB) 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. Queues of AVB traffic awaiting transmission during the idle guard band. Not empty;

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

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

[0025]

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

[0027] S32. AVB traffic to be transmitted currently The arrival time 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 set of AVB traffic to be transmitted using the aforementioned S1 to S3.

[0032]

[0033] S42. Transmit AVB traffic in the idle guard band according to the order of the AVB traffic sets to be transmitted, and 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 The deadline is as follows:

[0034]

[0035] The beneficial effects of this invention are as follows:

[0036] AVB traffic transmission is optimized by comprehensively considering AVB traffic and its deadlines. During the idle guard band, AVB streams are transmitted, and their priorities are redefined based on their deadlines. The earliest-delaying AVB traffic is placed in the guard band for transmission, ensuring that AVB traffic can be transmitted before its deadline as much as possible, thus reducing the risk of data loss. This strategy improves the success rate of AVB traffic transmission and the bandwidth utilization of the entire transmission link while ensuring TT traffic transmission latency and stability.

[0037] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0038] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0039] Figure 1 This is a diagram illustrating the principle of Time-Sensitive Network Traffic Transmission (TST).

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

[0041] Figure 3 This is a flowchart of the idle guard band traffic transmission process in the time-sensitive network traffic scheduling method based on the idle guard band proposed in this invention. Detailed Implementation

[0042] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed 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 are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

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

[0044] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, the terms describing positional relationships in the drawings are for illustrative purposes only and should not be construed as limiting the present invention. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0045] This invention primarily focuses on the transmission of TT and AVB traffic in time-sensitive networks. All traffic attributes F in the network... m This can be expressed as the following formula:

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

[0047] Where m represents the mth traffic to be transmitted, P represents the transmission period of the current traffic, TD represents the transmission duration of the current traffic, AT represents the time when the current traffic arrives in the transmission queue, and D represents the deadline of the current traffic.

[0048] If the current network traffic is schedulable, the difference between the traffic transmission time ST and the traffic arrival time AT in 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] Please see Figure 1 This is a schematic diagram of time-sensitive network traffic transmission. In time-sensitive network transmission systems, time-aware shapers are typically used to transmit traffic. Time-aware shapers are an enhancement feature defined by IEEE 802.1Qbv for planning traffic transmission. Figure 1The process of forwarding time-sensitive network traffic is demonstrated as follows: First, traffic enters the ingress port from input 1 and input 2, and then the forwarding route is determined by the switch engine before entering the priority filter. Next, the priority filter allocates network traffic to the corresponding priority queue based on the priority information carried by each time-sensitive network traffic. Then, the time-aware shaper controls the queue transmission gates to open and close periodically according to the Gate Control List (GCL), allocating a corresponding transmission time slice to each transmission queue.

[0051] For AVB stream transmission, Time-Sensitive Networking (TSN) uses a Credit Based Shaper (CBS) to control AVB traffic transmission. Specifically, AVB stream transmission will only proceed if the following conditions are met:

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

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

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

[0055] CBS controls the credit rating of AVB traffic based on bandwidth. The main parameters of CBS include IdleSlope and SendSlope, which are used to control the credit rating of current traffic. The relationship between the IdleSlope and SendSlope of AVB traffic is expressed by the following formula:

[0056] IdleSlope AVB +SendSlope AVB ≤MTR

[0057] Among them, IdleSlope AVB SendSlope represents the idle slope of AVB traffic. AVB IdleSlope represents the sending slope of AVB traffic, and MTR represents the maximum traffic transmission rate. Furthermore, IdleSlope and SendSlope continuously change as AVB traffic is transmitted.

[0058] Please see Figure 2 This is a schematic diagram illustrating the guard band mechanism principle of Time-Sensitive Networks (TSNs). Figure 2Taking a packet containing two transmission cycles as an example, each transmission cycle transmits traffic with 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 located before the boundary of each TT flow transmission cycle. The guard band represents an idle transmission time slice 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 guard band proposed in this invention mainly includes the following steps:

[0060] S1. Calculate the empty protection zone:

[0061] To ensure deterministic transmission of the TT stream, the guard band size is GB. size It is typically set to the maximum transmission time for all streams to be transmitted, specifically expressed by the following formula:

[0062] GB size =max{F TRT}, F∈F TSN

[0063] Where F TSN F represents time-sensitive network traffic. TRT This represents the transmission time of all pending time-sensitive network traffic. Because TT transmission is periodic, the start time of the idle guard band is GB. start This can be expressed as the following formula:

[0064]

[0065] in GB represents the periodic arrival time of the TT stream. size This indicates the size of the protective strip.

[0066] If the idle guard band is used for AVB traffic transmission, there may still be untransmitted traffic F before the guard band begins. unfinished The start time of this portion of traffic is in GB. start Previously, it was necessary to wait for this type of traffic to complete before transmitting AVB traffic during the guard band. Simultaneously, the difference between the end time of the current period's guard band and the end time of the uncompleted traffic was recorded as the idle guard band, yielding the specific available bandwidth for AVB traffic transmission. If the end time of the last transmitted traffic in the i-th transmission period is greater than or equal to the start time of the idle guard band, then the bandwidth of the i-th idle guard band is... This can be expressed as the following formula:

[0067]

[0068] in This represents the arrival time of the next transmission cycle of the i-th TT stream. This represents the end time of the last traffic in the i-th transmission cycle.

[0069] If the end time of the last transmission traffic in the i-th transmission cycle is less than the start time of the idle guard band, then the bandwidth of the i-th idle guard band is... This can be expressed as the following formula:

[0070]

[0071] S2. Determine AVB traffic transmission constraints:

[0072] AVB traffic transmission selection is constrained by CBS and requires the following two conditions to be met simultaneously:

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

[0074] 2. The current AVB traffic has a credit value greater than or equal to zero.

[0075] During the idle guard band setup, it is essential to ensure that the AVB queue transmission gate is open. The specific AVB traffic selection criteria during idle guard band transmission are as follows:

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

[0077]

[0078] in The idle slope and sending slope are calculated and constrained by the credit value changes that control the current traffic.

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

[0080]

[0081] in This represents the AVB traffic set.

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

[0083] This invention aims to maximize the success rate of AVB traffic transmission and improve the overall bandwidth utilization of the transmission link; therefore, transmission must be completed as early as possible before the AVB traffic deadline. Two key constraints must be followed when determining the AVB traffic to be transmitted:

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

[0085]

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

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

[0088]

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

[0090] S4. Perform traffic transmission:

[0091] Using the aforementioned S1 to S3, we can calculate a set of AVB traffic that should be transmitted. Subsequently, during the idle guard band, AVB traffic is transmitted based on this traffic set, as expressed by the following formula:

[0092]

[0093] During the idle guard band, AVB traffic is transmitted in the order of the AVB traffic sets to be transmitted. Simultaneously, the AVB traffic sets to be transmitted are continuously updated during transmission 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 It can be expressed as the following formula:

[0094]

[0095] According to S1 to S4 above, AVB traffic for the current period is transmitted within 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 set of AVB traffic to be transmitted, ensuring that AVB traffic can be transmitted before the deadline, until the idle guard band can no longer transmit AVB traffic.

[0096] This invention aims to address the adverse effects of the guard band mechanism, introduced to ensure deterministic TT (Time-Sensitive Broadband) traffic in Time-Sensitive Networks (TSNs), on AVB (Automatic Traffic Flow). To this end, a TSN traffic scheduling method based on idle guard bands is proposed.

[0097] Please see Figure 3 This invention proposes a time-sensitive network traffic scheduling method based on the idle guard band, including a flowchart of the idle guard band traffic transmission process. After traffic enters the time-sensitive network transmission system, it is based on... Figure 1 The gating list shown periodically opens and closes the transmission queue gates. Within a transmission cycle, after all traffic before the guard band has been transmitted, the AVB traffic transmission queue gate will be opened to transmit the traffic currently in the AVB queue. The specific steps are as follows:

[0098] Step 1. Determine traffic transmission constraints. This step is used to determine whether current network traffic is schedulable. It ensures that the difference between the current traffic's send time and arrival time, along with the sum of the current traffic's transmission time, is less than the deadline. This indicates that the current traffic is within a valid 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, then 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, then the start time of the idle guard band is equal to the end time of the last traffic.

[0100] Step 3. Determine if the idle guard band can transmit the minimum AVB traffic. Set the size of the idle guard band for the current transmission cycle and compare it with the minimum transmission time of the AVB traffic. If the idle guard band is less than the minimum transmission time of the AVB traffic, it means that the current idle guard band cannot transmit any AVB traffic, and directly proceed to the next transmission cycle; if the idle guard band is greater 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 proceed to Step 4.

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

[0102] If the current AVB queue transmission gate is open and the credit value of the current AVB traffic is greater than or equal to zero, and 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, then the determination of the AVB traffic to be transmitted begins, using the following method:

[0103] If the deadline of the selected AVB stream is the earliest among all candidate AVB streams, and the arrival time of the candidate AVB stream is the earliest, then proceed 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 guard band end time, end the current transmission cycle and prepare for the next transmission cycle; otherwise, repeat step 5.

[0105] This invention aims to solve the deterministic transmission problem of TT traffic in Time-Sensitive Networks (TSNs), particularly addressing the potential adverse effects of guard band mechanisms on AVB traffic. To this end, this invention proposes a TSN traffic scheduling method based on idle guard bands. By rationally utilizing idle guard bands in the network for efficient transmission of AVB traffic, it ensures that AVB traffic can successfully complete its transmission task before the specified deadline. Furthermore, this invention utilizes previously unused idle bandwidth resources, thereby improving the bandwidth utilization of the entire transmission link, achieving optimized resource allocation and improved network performance. During the idle guard band, AVB streams are transmitted, and their priorities are redefined according to their deadlines. The earliest-delaying AVB traffic is filled into the guard band for transmission, ensuring that AVB traffic can complete its transmission as early as possible before the deadline, thus reducing the risk of data loss. This method not only guarantees the deterministic transmission of TT traffic but also accommodates the transmission needs of AVB traffic, achieving efficient coordination of different types of traffic and optimized utilization of network resources in TSNs.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A time-sensitive network traffic scheduling method based on idle guard band, characterized in that... Includes the following steps: S1. Calculate the empty protection zone, the specific process is as follows: S11. Calculate the size of the free guardrail (GB) size : GB size =max{F TRT },F∈F TSN Among them, F TSN F represents time-sensitive network traffic. TRT Represents the transmission time of all time-sensitive network traffic awaiting transmission; S12. Calculate the start time of the idle guard band (GB) start : in, This 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 traffic in 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, This indicates the arrival time of the next transmission cycle for the i-th TT traffic; S2. Determine the audio-video bridging (AVB) 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. Queues of AVB traffic awaiting transmission during the idle guard band. Not empty; S3. Determine the AVB traffic that should be transmitted now. The specific process is as follows: S31. Current AVB traffic to be transmitted The deadline should be earlier than the deadline of all pending AVB traffic. in, Represents the deadline for the i-th AVB traffic to be transmitted; S32. AVB traffic to be transmitted currently The arrival time 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 set of AVB traffic to be transmitted using the aforementioned S1 to S3. S42. Transmit AVB traffic in the idle guard band according to the order of the AVB traffic sets to be transmitted, and 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 The deadline is as follows:

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

3. The time-sensitive network traffic scheduling method based on idle guard band according to claim 1, characterized in that: Before step S1, a step is added to determine that there is no traffic to be transmitted with a higher priority than AVB traffic in the current transmission time slice. This step is used to control the current traffic credit value, as follows: IdleSlope AVB +SendSlope AVB ≤MTR Among them, IdleSlope AVB SendSlope represents the idle slope of AVB traffic. AVB The transmit slope represents the AVB traffic, and MTR represents the maximum data transfer rate.

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

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