A lossless flow control method for deterministic networks

Abstract

The application discloses a lossless flow control method suitable for a deterministic network, which comprises that a switch sends a flow control frame to an upper network node to control data transmission of a best effort flow queue of the upper network node. The upper network node receives the flow control frame sent by the switch, and preferentially sends high-priority flow queue data according to an integration strategy of the deterministic network and sends best effort flow queue data according to a strict priority strategy. Meanwhile, the switch preferentially sends high-priority flow queue data according to the integration strategy of the deterministic network and sends best effort flow queue data according to the strict priority strategy according to the received flow control frame of a lower network switch. The switch switches different input devices according to waiting time, so that different input devices can be ensured to be sent.

Description

Technical Field

[0001] This invention belongs to the field of lossless flow control technology, and specifically relates to a lossless flow control method suitable for deterministic networks. Background Technology

[0002] The IEEE 802.3 standard defines ordinary Ethernet, which defines media access control methods for the physical layer and data link layer for wired Ethernet, and implements a best-effort transmission policy to transmit Ethernet traffic.

[0003] Time-Triggered Ethernet (TTE) defines time-triggered traffic, rate-limited traffic, and best-effort traffic. Time-triggered traffic has strict end-to-end latency and jitter, while rate-limited traffic has an end-to-end latency cap. Both of these types of traffic can guarantee quality of service. However, best-effort traffic has no quality of service requirements. Therefore, when the data bandwidth exceeds the network transmission bandwidth, best-effort traffic may experience packet loss.

[0004] Time-Sensitive Networking (TSN) provides Time-Awareness Shaper (TAS), Credit-Based Shaper (CBS), Asynchronous Traffic Shaper (ATS), and Cyclic Queuing and Forwarding (CQF) Shaper. TAS offers strict end-to-end latency control and low jitter, while traffic shaped by CBS, ATS, and CQF guarantees an end-to-end latency cap. TSN networks are compatible with Ethernet as defined by the IEEE 802.3 standard, but lack a corresponding shaping mechanism for best-effort traffic, thus failing to guarantee quality of service for best-effort traffic, which is also susceptible to packet loss.

[0005] In safety-critical domains, although best-effort traffic in deterministic networks has a lower priority, it still needs to be guaranteed to be delivered without packet loss to meet the application requirements of safety-critical systems. Therefore, flow control mechanisms are needed for best-effort traffic to ensure that packet loss does not occur during transmission. Summary of the Invention

[0006] To ensure that best-effort traffic transmission in deterministic networks does not suffer packet loss, this invention proposes a lossless flow control method suitable for deterministic networks. This method can provide packet-free transmission services for deterministic networks.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A lossless flow control method applicable to deterministic networks, the method comprising:

[0009] Step 1: After the network is powered on, starting from the source node, l c+1 When the best-effort traffic queue buffer on the output port of the network switch is empty, it sends traffic to the l c Level network nodes send flow control frames to inform l c The current network node can send the best possible transmission traffic;

[0010] Step Two: c Level network node receives l c+1 The system receives flow control frames from the primary switch and then sends high-priority traffic according to the deterministic network scheduling policy, while transmitting best-effort traffic queue data packets according to the strict priority scheduling policy.

[0011] Step 3: l c+1 Level switches transmit high-priority traffic and best-effort traffic according to the integration strategy of deterministic networks. c+1 The level switch received l c+2 When a flow control frame is received from a high-level switch, the best-effort traffic queue data packets are sent according to a strict priority policy until the best-effort traffic queue is empty.

[0012] Step 4: Other switches in the deterministic network control and transmit high-priority traffic and best-effort traffic in accordance with steps 1 to 3.

[0013] Furthermore, in step one, when the queue buffer for all BE traffic transmissions on the output port is empty, the deterministic network switch sends a flow control frame (TCF) to the input device on the input port, informing the input device that BE traffic can be transmitted at present; the type of the flow control frame (TCF) is event-triggered bandwidth-limited traffic, and its priority is higher than that of BE traffic.

[0014] Furthermore, in step one, after the network is powered on, on the BE traffic transmission path, starting from the l0 level source node, when the l1 level network switch has an empty BE traffic queue buffer on its output port, it sends a TCF to the source node to inform the source node that it can currently send BE traffic; when the l2 level network switch has an empty BE traffic queue buffer on its output port, it sends a TCF to the l1 level network switch to inform the l1 level network switch that it can currently send BE traffic; and so on, until the last level network switch.

[0015] Furthermore, in step one, the network switch compares the buffer depth of its own BE traffic queue with the buffer depth of the BE traffic queue of the connected input devices, and selects different numbers of input devices to send flow control frames (TCF).

[0016] If the BE traffic buffer depth of the network switch output port is BD Sq =n, and the BE flow buffer depth of the input device output port is BD. ND If m = n, then k input devices are selected each time to send flow control frames, where k = n / m, and k is a positive integer;

[0017] The network switch first sends a flow control frame (TCF) to the 1 to k input port devices. Then, when the BE flow queue buffer of the network switch output port is empty, it sends a flow control frame (TCF) to the k+1 to 2k input devices, and so on, until the last input device is notified.

[0018] Furthermore, if the network switch waits for a time interval longer than (δ+FL / BW) and the input device still does not send any BE traffic data packet to the network switch, the network switch determines that the current input device has completed the transmission of all BE traffic and will send a flow control frame (TCF) to the input device in the next round. δ is the time synchronization precision of the deterministic network, FL is the maximum transmission frame length of the specified network, and BW is the port transmission bandwidth of the specified network.

[0019] Furthermore, in step two, l c Level network node receives l c+1 The flow control frame (TCF) sent by the primary switch first transmits high-priority traffic, and then schedules the BE traffic queue data packets according to a strict priority policy; the flow control frame (TCF) only affects the transmission of BE traffic queues, and does not affect the normal transmission of high-priority traffic.

[0020] Furthermore, in step two, the BE traffic queue transmits data in order of priority;

[0021] Furthermore, in step two, l c If a new data packet continues to be received in the queue currently transmitting BE traffic during the transmission of BE traffic, the BE node will save the new data packet in the queue and will not schedule its transmission again.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) The method of the present invention fully considers the connection characteristics of deterministic networks and is applicable to switching networks with various topologies such as star and ring.

[0024] (2) The method of the present invention takes into account the transmission characteristics of deterministic networks. The flow control method provided can be compatible with the existing scheduling mechanism of deterministic networks, avoid the conflict between lossless flow control and the existing scheduling mechanism, and improve the reliability of deterministic network operation.

[0025] (3) The method of the present invention takes into account the strict requirements of deterministic networks in security-critical fields, and the proposed lossless flow control method can provide a service guarantee of no packet loss for best-effort transmission traffic.

[0026] (4) The lossless flow control method provided by the present invention can be flexibly configured according to design requirements. It can not only guarantee the minimum bandwidth of low-priority best-effort flow transmission, but also guarantee the real-time performance of high-priority best-effort flow transmission.

[0027] (5) The method provided by the present invention can be used in conjunction with existing scheduling methods for deterministic networks, or it can be used independently as a scheduling mechanism in deterministic networks. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the physical topology of a deterministic network illustrated in the embodiments;

[0029] Figure 2 It is a queuing mechanism within deterministic network nodes;

[0030] Figure 3 This is a schematic diagram of data transmission in the lossless flow control method proposed in this invention;

[0031] Figure 4 This is a schematic flowchart of the lossless flow control method proposed in this invention. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0033] In this invention, end systems (ES) and switches in a deterministic network are connected via bidirectional communication links. The end system acts as both a source node and a destination node according to the "end-to-end" role of the communication task; network devices containing forwarding and multiplexing functions are called "switches." End systems and switching devices are collectively referred to as "nodes." For example, Figure 1 The diagram shows an example topology of the physical connections of a deterministic network.

[0034] In this invention, the physical topology of the deterministic network includes multiple end systems and switches, denoted as a set ND = {ES1, ES2, ES3, ..., ES...} p ,...,ES P S1, S2, S3, ..., Sq ,…,S Q}, ES1 indicates that it belongs to the first end system in ND, ES2 indicates that it belongs to the second end system in ND, ES3 indicates that it belongs to the third end system in ND, ES P This indicates that it belongs to the last end system in ND, and the subscript p represents the identifier of the end system in ND. For ease of explanation, ES p It also indicates belonging to any end system in the ND; S1 indicates belonging to the first switch in the ND, S2 indicates belonging to the second switch in the ND, S3 indicates belonging to the third switch in the ND, S... Q This indicates the last switch in the ND (Distributed Network), and the subscript 'q' represents the identifier of the switch in the ND. For ease of explanation, S... q It also means that it belongs to any switch in the ND.

[0035] In this invention, within a deterministic network, the output ports of end systems and switches have multiple output queues with different priorities, such as... Figure 2 As shown, there are a maximum of 8 priority queues, with priority decreasing from 0 to 7. The priority queue depth for each output port of the network node is uniformly BD. ND The subscript ND indicates the priority queue depth of the output port belonging to the network node ND.

[0036] For example: This indicates the priority queue depth of the output port in switch S1.

[0037] In this invention, the time synchronization accuracy δ of a deterministic network refers to the maximum difference between any two synchronization clocks within a time synchronization period.

[0038] In this invention, FL refers to the maximum transmission frame length of a deterministic network, and BW refers to the port transmission bandwidth of a deterministic network.

[0039] In this invention, the deterministic network end system and switch integrate the transmission of high-priority traffic (time-triggered traffic, time-aware traffic, time-sensitive traffic, bandwidth-constrained traffic, etc.) and low-priority traffic (best-effort traffic, BE) according to the SAE AS6802 standard protocol and the IEEE 802.1Qbv standard protocol. Best-effort traffic has a lower priority and can be allocated to one or more priority queues according to application needs.

[0040] In this invention, when designing and planning a deterministic network, it is necessary to ensure the minimum transmission bandwidth for each priority queue, so that the lowest priority best-effort transmission traffic can have a chance to be transmitted.

[0041] In this invention, when the queue buffers for all BE traffic transmissions on the output port are empty, the deterministic network switch sends a Traffic Control Frame (TCF) to the input device on the input port, informing the input device that BE traffic can currently be transmitted. The TCF is of type event-triggered bandwidth-limited traffic, and its priority is higher than that of BE traffic.

[0042] In this invention, the 6th and 7th queues on the output port of the deterministic network node are BE traffic queues, and the remaining queues are high-priority traffic queues.

[0043] In this invention, based on the distance to the source node ES p The hop count (Hops) is used to classify the network nodes along the BE traffic transmission path into network layers: Level = {l0, l1, l2, ..., l...}. c , ..., l C The division of the network switch into its final level is as follows: In this invention, the source node is designated as the starting node of the BE traffic transmission path, and is denoted as level l0. The network switch belonging to the last level of the BE traffic transmission path is denoted as level l. C For ease of explanation, l c It also refers to any switch on the BE traffic transmission path.

[0044] This invention proposes a lossless flow control method suitable for deterministic networks. The method includes a switch sending flow control frames to the next-level network node to control the data transmission of the best-efforts transmission queue. Upon receiving the flow control frame from the switch, the next-level network node prioritizes sending high-priority traffic queue data according to the deterministic network integration strategy and sends best-efforts transmission traffic queue data according to a strict priority strategy. Simultaneously, the switch, based on the received flow control frames from the next-level network switch, prioritizes sending high-priority traffic queue data according to the deterministic network integration strategy and sends best-efforts transmission traffic queue data according to a strict priority strategy. The switch switches different input devices based on waiting time to ensure that different input devices can receive transmission. During transmission, the network node strives to transmit newly received data packets and will not schedule further transmission of newly received data packets, ensuring that all best-efforts transmission traffic queue data packets have a chance to be sent.

[0045] This invention proposes a lossless flow control method suitable for deterministic networks, which can be used in conjunction with existing deterministic network scheduling methods, or can be applied independently as a lossless flow control method in deterministic networks.

[0046] See Figure 4 As shown, a lossless flow control method suitable for deterministic networks includes the following steps:

[0047] Step 1: After the network is powered on, starting from the source node, it makes every effort to transmit traffic along the transmission path. c+1 When the best-effort traffic queue buffer on the output port of the network switch is empty, it sends traffic to the l c Level network nodes send flow control frames to inform l c The current network node can send the best possible transmission traffic;

[0048] Step Two: c Level network node receives l c+1 The system receives flow control frames from the primary switch and then sends high-priority traffic according to the deterministic network scheduling policy, while transmitting best-effort traffic queue data packets according to the strict priority scheduling policy.

[0049] Step 3: l c+1 The level switch sends high-priority traffic according to the deterministic network scheduling policy and transmits best-effort traffic queue packets according to the strict priority scheduling policy. c+1 The level switch received l c+2 When a flow control frame is received from a high-level switch, the best-effort traffic queue data packets are sent according to a strict priority policy until the best-effort traffic queue is empty.

[0050] Step 4: Other switches in the deterministic network control and transmit high-priority traffic and best-effort traffic in accordance with steps 1 to 3;

[0051] In this invention, steps one through four are used to schedule and transmit all nodes of the deterministic network to transmit traffic with all-out effort, which can achieve packet loss-free transmission of traffic with all-out effort.

[0052] Step 1: After the network is powered on, starting from the source node, it makes every effort to transmit traffic along the transmission path. c+1 When the best-effort traffic queue buffer on the output port of the network switch is empty, it sends traffic to the l c Level network nodes send flow control frames to inform l c The current network node can send the best possible transmission traffic;

[0053] In this invention, after the network is powered on, on the BE traffic transmission path, starting from the level 10 source node, the level 11 network switch sends a TCF to the source node to inform the source node that it can currently send BE traffic when the BE traffic queue buffer of its output port is empty; the level 12 network switch sends a TCF to the level 11 network switch to inform the level 11 network switch that it can currently send BE traffic when the BE traffic queue buffer of its output port is empty; and so on, until the last level network switch.

[0054] In this invention, the network switch selects a different number of input devices to send TCF based on a comparison between its own BE traffic queue buffer depth and the BE traffic queue buffer depth of the connected input devices. Specifically, if the BE traffic buffer depth of the network switch output port is... The BE flow buffer depth of the input device output port is BD. ND =m, then each time k input devices (k=n / m, where k is a positive integer) are selected to send flow control frames. That is, the network switch first sends TCF to the 1 to k input port devices, and then when the BE flow queue buffer of the network switch output port is empty, it sends TCF to the k+1 to 2k input devices, and so on, until the last input device is notified.

[0055] In this invention, if the switch waits for a time interval longer than (δ+FL / BW) and the input device still does not send any BE traffic data packet to the switch, the switch determines that the current input device has completed the transmission of all BE traffic and will send a TCF to the input device in the next round to inform the input device that it can send BE traffic now.

[0056] For example, see as Figure 1 , Figure 3 As shown, at time t1, when its own BE traffic queue buffer is empty, switch S1 sends a TCF to end system ES1, informing end system ES1 that it can currently send BE traffic. At time t3, switch S1 has waited for a time interval longer than δ+FL / BW without receiving a BE traffic data packet from end system ES1, and its BE traffic queue buffer is currently empty. Therefore, switch S1 sends a TCF to end system ES2, informing end system ES2 that it can currently send BE traffic.

[0057] Step Two: c Level network node receives l c+1 The system receives flow control frames from the primary switch and then sends high-priority traffic according to the deterministic network scheduling policy, while transmitting best-effort traffic queue data packets according to the strict priority scheduling policy.

[0058] In this invention, l c Level network node receives l c+1 The TCF (Transmission Control Message) sent by the primary switch is then processed according to the SAE AS6802 standard protocol or the IEEE 802.1Qbv standard protocol. High-priority traffic (time-triggered traffic, time-aware traffic, time-sensitive traffic, bandwidth-constrained traffic, etc.) is transmitted first, and then the BE (Blocking Entity) traffic queue data packets are scheduled according to a strict priority policy. The TCF only affects the transmission of BE traffic queues and does not affect the normal transmission of high-priority traffic.

[0059] In this invention, l c If a new data packet continues to be received in the queue currently transmitting BE traffic during the transmission of BE traffic, the BE node will save the new data packet in the queue.

[0060] In this invention, BE traffic queues are transmitted in order of priority. This ensures that low-priority queues have a chance to be transmitted in each transmission, preventing them from becoming "starved" due to lack of transmission opportunities.

[0061] Specifically, when end system ES1 receives the TCF sent by switch S1, it transmits data packets in queues 0 to 5 according to the SAE AS6802 standard protocol or the IEEE 802.1Qbv standard protocol, and then transmits BE traffic data packets in queues 6 to 7 according to a strict priority policy.

[0062] For example, see as Figure 1 , Figure 3 As shown, at time t2, after receiving the TCF from switch S1, end system ES1 sends high-priority traffic data packets 101, 102, and 103 according to the deterministic network scheduling policy, and then sends BE traffic queue data packets 106 and 107 according to the strict priority policy. At time t3, after receiving the TCF from switch S1, end system ES2 sends BE traffic queue data packets 206 and 207 according to the strict priority policy. During the period from time t3 to time t4, end system ES2 sends high-priority traffic data packets 201, 203, and 204 according to the deterministic network scheduling policy, unaffected by the TCF.

[0063] Step 3: l c+1 Level switches transmit high-priority traffic and best-effort traffic according to the integration strategy of deterministic networks. c+1 The level switch received l c+2 When a flow control frame is received from a high-level switch, the best-effort traffic queue data packets are sent according to a strict priority policy until the best-effort traffic queue is empty.

[0064] In this invention, the network switch first transmits high-priority traffic (time-triggered traffic, time-aware traffic, time-sensitive traffic, bandwidth-constrained traffic, etc.) according to the SAE AS6802 standard protocol or the IEEE 802.1Qbv standard protocol, and then schedules BE traffic queue data packets according to a strict priority strategy. Flow control frames only affect the transmission of BE traffic queues and do not affect the normal transmission of high-priority traffic.

[0065] In this invention, the switch sends flow control frames to control the transmission of BE traffic of the upstream network node, while the end systems (source node and destination node) do not send flow control frames.

[0066] In this invention, l c+1 If a new data packet continues to be received in the queue of the current BE traffic transmission during the transmission of BE traffic by a network switch, the new data packet will be stored in the queue and will not be scheduled for transmission in the next round of data transmission.

[0067] In this invention, if l c+1 A network switch of level 1 waits for a time interval longer than (δ+FL / BW), l c The network nodes at the level still have not sent to l c+1 If a level switch sends arbitrary BE traffic data packets, then l c+1 The level switch identifies the current l c The first-level network node has completed the transmission of all BE traffic and will send the TCF to the next round of nodes. c Level network node, inform l c The current network node can send BE traffic.

[0068] In this invention, l C+1 A level network switch is the last-level switch on the data transmission path, then l C+1 The primary switch will not receive flow control frames from the end system, therefore it transmits high-priority traffic according to the deterministic network integration strategy and schedules BE traffic queue packets according to the strict priority strategy.

[0069] Specifically, for example, see Figure 1 , Figure 3 As shown, since the end system ES3 connected to switch S1 is the destination of the data transmission path, switch S1 prioritizes sending high-priority traffic data packets 101, 102, 103, 201, 203 and 204 according to the deterministic network integration strategy, and sends best-effort traffic queue data packets 106 and 107 according to strict priority.

[0070] Step 4: Other switches in the deterministic network control and transmit high-priority traffic and best-effort traffic in accordance with steps 1 to 3;

[0071] The lossless flow control method for deterministic networks shown in this embodiment can be used in conjunction with existing flow scheduling and control methods for deterministic networks, or it can be applied independently as a flow control method to deterministic networks.

[0072] It is understood that those skilled in the art can make equivalent substitutions or modifications to the technical solution and inventive concept of the present invention, and all such substitutions or modifications should fall within the protection scope of the appended claims.

Claims

1. A lossless flow control method suitable for deterministic networks, characterized in that, The method includes: Step 1: After the network is powered on, starting from the source node, l c+1 When the best-effort traffic queue buffer on the output port of the network switch is empty, it sends traffic to the l c Level network nodes send flow control frames to inform l c The current network node can send the best possible transmission traffic; Step Two: c Level network node receives l c+1 The system receives flow control frames from the primary switch and then sends high-priority traffic according to the deterministic network scheduling policy, while transmitting best-effort traffic queue data packets according to the strict priority scheduling policy. Step 3: l c+1 Level switches transmit high-priority traffic and best-effort traffic according to the integration strategy of deterministic networks. c+1 The level switch received l c+2 When a flow control frame is received from a high-level switch, the best-effort traffic queue data packets are sent according to a strict priority policy until the best-effort traffic queue is empty. Step 4: Other switches in the deterministic network control and transmit high-priority traffic and best-effort traffic in accordance with steps 1 to 3.

2. The lossless flow control method for deterministic networks according to claim 1, characterized in that, In step one, when the queue buffer for all BE traffic transmissions on the output port is empty, the deterministic network switch sends a flow control frame (TCF) to the input device on the input port, informing the input device that BE traffic can be transmitted at this time. The type of the flow control frame (TCF) is event-triggered bandwidth-limited traffic, and its priority is higher than that of BE traffic.

3. The lossless flow control method for deterministic networks according to claim 1, characterized in that, In step one, after the network is powered on, on the BE traffic transmission path, starting from the l0 level source node, the l1 level network switch sends a TCF to the source node when the BE traffic queue buffer on the output port is empty, informing the source node that BE traffic can be sent at this time; the l2 level network switch sends a TCF to the l1 level network switch when the BE traffic queue buffer on the output port is empty, informing the l1 level network switch that BE traffic can be sent at this time; and so on, until the last level network switch.

4. The lossless flow control method for deterministic networks according to claim 1, characterized in that, In step one, the network switch compares the buffer depth of its own BE traffic queue with the buffer depth of the BE traffic queue of the connected input devices, and selects different numbers of input devices to send flow control frames (TCF). If the BE traffic buffer depth of the network switch output port is The BE flow buffer depth of the input device output port is BD. ND If m = n, then k input devices are selected each time to send flow control frames, where k = n / m, and k is a positive integer; The network switch first sends a flow control frame (TCF) to the 1 to k input port devices. Then, when the BE flow queue buffer of the network switch output port is empty, it sends a flow control frame (TCF) to the k+1 to 2k input devices, and so on, until the last input device is notified.

5. The lossless flow control method for deterministic networks according to claim 1, characterized in that, If the network switch waits for a time interval longer than (δ+FL / BW) and the input device still has not sent any BE traffic data packet to the network switch, the network switch determines that the current input device has completed the transmission of all BE traffic and will send a flow control frame (TCF) to the input device in the next round. δ is the time synchronization precision of the deterministic network, FL is the maximum transmission frame length of the determinate network, and BW is the port transmission bandwidth of the determinate network.

6. The lossless flow control method for deterministic networks according to claim 1, characterized in that, In step two, l c Level network node receives l c+1 The flow control frame (TCF) sent by the primary switch first transmits high-priority traffic, and then schedules the BE traffic queue data packets according to a strict priority policy; the flow control frame (TCF) only affects the transmission of BE traffic queues, and does not affect the normal transmission of high-priority traffic.

7. A lossless flow control method for deterministic networks according to claim 6, characterized in that, In step two, the BE traffic queue transmits traffic in order of priority.

8. A lossless flow control method for deterministic networks according to claim 7, characterized in that, In step two, l c If a new data packet continues to be received in the queue currently transmitting BE traffic during the transmission of BE traffic, the BE node will save the new data packet in the queue and will not schedule its transmission again.

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