Low-orbit constellation time-sensitive service span transmission method

Abstract

The invention discloses a low-orbit constellation time-sensitive service span transmission method, which comprises the following steps of: in a low-orbit constellation based on laser interconnection, acquiring IP addresses of satellites and a laser connection information table; performing adjacent satellite connection initialization and routing planning on each satellite node, performing thumbnail according to a traffic weight and a strong connectivity algorithm, and dividing the whole satellite constellation into a plurality of parallel subnets; fast arrangement is carried out according to VLAN labels marked on data packet frame headers by source nodes during flow transmission; the time-sensitive services with high priorities are output through two controllable doors which are periodically switched, opened and closed; and finally, replanning a route according to the flow, and realizing cross-long-distance connection of the time-sensitive service. According to the low-orbit constellation time-sensitive service span transmission method provided by the invention, the situation that the time-sensitive service transmission delay is too high and uncontrollable due to congestion occurring during traffic transmission under a parallel subnet structure is optimized, and the time-sensitive service transmission result meets the controllable, predictable and low-delay conditions.

Description

Technical Field

[0001] The present invention relates to a transmission scheduling method, and in particular to a span transmission method for time-sensitive services of a low-orbit constellation. Background Art

[0002] At present, the research on satellite networking is mainly based on the existing microwave communication transmission technology, mainly small-scale networking and satellite-to-ground communication. The link scheduling scheme is not applicable to the low-orbit giant constellation under the current intersatellite laser interconnection background. Nowadays, the number of satellites has increased sharply, the scale of networking has expanded, and laser communication schemes are expected to be adopted between satellites. In the context of tens of thousands of satellites, the number of routing hops increases and the delay increases after dense satellite networking, and the advantages of laser communication are exhausted. At present, traditional satellite networking schemes cannot give full play to the ultra-low latency advantages brought by tens of thousands of satellite networking and intersatellite laser communication. At the same time, with the increasing complexity of space communication tasks, the demand for time-sensitive services is increasing, which poses new challenges to information transmission. On the one hand, the internal system of the satellite is required to have high bandwidth, reliability and real-time performance; on the other hand, intersatellite communication formed by wireless links also needs to have low latency and high reliability. However, when business data is transmitted jointly through the wired link inside the satellite and the wireless link between satellites, it may cause node congestion and uncontrollable transmission delay, thus failing to guarantee the real-time transmission of time-sensitive services. Summary of the invention

[0003] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is that the existing time-sensitive service transmission method is not suitable for giant satellite constellations. In the context of tens of thousands of satellites, the number of routing hops increases and the delay increases after dense satellite networking, which cannot meet the requirements of low delay and controllable delay for time-sensitive services. Therefore, the present invention provides a method for span transmission of time-sensitive services in low-orbit constellations: based on a parallel subnet structure, it ensures that the inter-satellite transmission delay is controllable and meets the transmission delay requirements, and realizes controllable and predictable delay of the entire process through queuing processing and forwarding scheduling of service data packets inside the satellite.

[0004] To achieve the above object, the present invention provides a method for span transmission of time-sensitive services of a low-orbit constellation, comprising the following steps:

[0005] Obtain the IP address of each satellite and the laser connection information table; Based on the laser connection information table, each satellite node initializes the connection with the adjacent satellite and plans the route according to the traditional path algorithm. After screening the initial important links by the set threshold, the map is reduced according to the traffic weight and strong connectivity algorithm, and the entire satellite constellation is divided into several parallel subnets;

[0006] Traffic is routed in the constructed parallel subnets, and each packet includes basic information required for transmission and characteristics related to priority sorting;

[0007] Firstly, the VLAN tag added by the source node to the data packet frame header during traffic transmission is roughly classified, and then the weighted priority scheduling algorithm is used to quickly sort the priorities.

[0008] The periodic forwarding mechanism in the 802.1Qch protocol is used to output high-priority time-sensitive services through two controllable gates that are periodically switched on and off;

[0009] Finally, the route is re-planned according to the traffic volume to achieve long-distance connection and predictable transmission delay for time-sensitive services.

[0010] Furthermore, each satellite has a laser connection information table, which records the satellites to which each satellite is currently connected, the satellite IPs within the laser reachable range at the current moment, and their position logical addresses; wherein, the satellite IPs within the laser reachable range are the satellite IPs to which each satellite can adjust the laser for connection, and the position logical addresses are the current position information of all satellites to which each satellite can connect, and the laser connection information table is continuously updated as the satellite position changes.

[0011] Furthermore, the satellite logical addresses in the laser connection information table are used to find the satellites in front and behind each satellite in the same orbit and the left and right satellites in the adjacent orbit, so as to complete the connection initialization of each satellite, and the initial cost of each link is equal; based on the connection status of each link after initialization, the traditional Dijkstra algorithm is used to plan routes for various current communication requests, obtain the traffic status of each inter-satellite link, and calculate the cost of each link; select important links and create directed traffic based on important links.

[0012] Furthermore, traffic routing is performed based on multiple parallel subnets, and the traffic is simulated traffic that takes into account real-life communication needs and large-scale satellite constellation routing.

[0013] Furthermore, each satellite-scheduled data service has specific requirements for latency, bandwidth, jitter, and VLAN tags.

[0014] Furthermore, for these data packets with transmission requirement information, when performing cross-distance transmission between subnets, in order to meet the transmission requirements of time-sensitive services, the data packets in the node buffer queue need to be positioned according to their service priorities.

[0015] Further, according to the VLAN tag, the VLAN tag priority of all services stored in the sending port is determined, which is generally set to P i= 0-7. Sort these data packets by label priority first. The higher the priority, the earlier they are sent. For data packets with the same priority, a weighted priority algorithm is used to sort them for the second time. The basic principle is a linear weighted method, which evaluates the impact of the key parameters carried by the data packet on the transmission. Assume that at time t, the data packets in the cache queue of congested node i are S packets with different priorities. 1 ,S 2 ,…,S n , which has been arranged by label priority, assuming that S n , S n-1 , S n-2 The present invention considers several factors that have a greater impact on the transmission of time-sensitive service data packets: transmission delay constraint D, transmission bandwidth constraint B and transmission distance constraint J, e i is the influencing factor. The subdivision priority formula of the weighted priority ranking algorithm is:

[0016] P t =e 1 ·D+e 2 ·B+e 3 ·J.

[0017] Furthermore, two thresholds η are defined: 1 and η 2 , η 1 To send the threshold as quickly as possible, η 1 is the congestion retransmission threshold. After adjusting the position of the services in the cache queue, the low-priority services located after the congestion retransmission threshold are discarded, and a message is sent to notify the discarded low-priority service source node to reselect a route for it. The high-priority time-sensitive services located before the as soon as possible transmission threshold are ready for span transmission. For high-priority time-sensitive services, the periodic cyclic scheduling and forwarding mechanism is used to forward them.

[0018] Furthermore, the satellite physical layer responsible for the forwarding function also includes a TSN switch SW that can undertake the time-sensitive service transmission function. Utilizing the characteristics of SW, a gating scheduling based on the odd-even time period rotation and with a time protection period is performed for the transmission of time-sensitive services.

[0019] Furthermore, the timer module in the SW is used to control the opening and closing of the transmission gate of the forwarding port. 7 Queues and Q 6 The queue with the highest priority is used to transmit time-sensitive services. Assume that the timer is set to T 0 The time starts, and the Q in SW 7 The number queue is opened to transmit data and closed to write data. 6The queue is opened to write data and closed to transmit data. After a period of time d, the timer module reaches the threshold T 0 +d, this time flips the status of the two queues, Q 7 The queue is opened to write data and closed to send data. 6 The number queue is closed for writing data and opened for transmitting data. Considering that in some cases, TSN data packets may be transmitted after the secondary priority services, the secondary priority data packets are too large, which will lead to the failure to meet the transmission delay requirements of time-sensitive services and even cause congestion of time-sensitive services. In view of this situation, the present invention extends the time period d before the time period of time-sensitive services to be transmitted. offset (usually the transmission time of a standard Ethernet frame), no secondary priority services can be transmitted during this time period. Therefore, the time point when the transmission gate is opened and closed becomes T 0 +d+d offset .

[0020] Furthermore, after introducing the parallel subnet structure, weighted priority arrangement algorithm and odd-even gated cyclic queuing forwarding mechanism, the present invention realizes the controllable delay of long-distance transmission between time-sensitive service subnets. First, when the time-sensitive service data packet and the secondary priority data packet arrive at the transmission port of the subnet transmission satellite, the time overhead of arranging these data packets is D S The delay of periodic queuing forwarding at the transmission port is D in the worst case. Q =2d+d offset , jitter is 0 to 2d+d offset When the transmission is performed over a long distance via a parallel subnet, the transmission delay D can be calculated using the laser transmission information table. T Therefore, we can conclude that the controllable delay of span transmission is:

[0021] D Total =D S +D Q +D T .

[0022] Furthermore, the parallel subnet structure performs end-to-end cross-distance transmission to meet business transmission requirements.

[0023] Technical Effects

[0024] Today, ultra-large-scale constellations are being networked and expanded, and laser communication solutions are expected to be used between satellites. After dense satellite networking, the number of routing hops increases, the latency increases, and the advantages of laser communication are exhausted. The multiple parallel subnet structure makes up for the ultra-low latency advantage that traditional satellite networking solutions cannot maintain. It can be applied to the cross-distance transmission scenarios of time-sensitive services, and by optimizing the hardware and forwarding mechanism of the satellites in the parallel subnets, the combination of the two can ensure that the latency meets the requirements and meets the controllable and predictable conditions.

[0025] A method for span transmission of time-sensitive services of a low-orbit constellation of the present invention optimizes the situation in which the time-sensitive service transmission delay is too high and uncontrollable due to congestion when transmitting traffic under a parallel subnet structure, through a parallel subnet structure, simulated real-time traffic service routing, a weighted priority algorithm for rapid service segmentation, a periodic gated forwarding mechanism, and span laser transmission between subnets. The result of the time-sensitive service transmission satisfies the controllable, predictable and low-delay conditions.

[0026] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a method for span transmission of time-sensitive services of a low-orbit constellation according to a preferred embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of parallel subnet structure division in a method for span transmission of time-sensitive services of a low-orbit constellation according to a preferred embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of arranging services by a weighted priority algorithm in a method for span transmission of time-sensitive services of a low-orbit constellation according to a preferred embodiment of the present invention;

[0030] Figure 4 It is a schematic diagram of a gated scheduling based on a rotation of odd and even time periods and having a time protection period in a method for span transmission of time-sensitive services of a low-orbit constellation according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the example diagrams in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] like Figure 1 As shown, an embodiment of the present invention provides a method for span transmission of time-sensitive services of a low-orbit constellation, comprising the following steps:

[0033] Step 100, each satellite has a laser connection information table, which records the satellites that each satellite is currently connected to, the satellite IPs within the laser reachable range at the current moment, and their position logical addresses; wherein, the satellite IPs within the laser reachable range are the satellite IPs to which each satellite can adjust the laser for connection, and the position logical addresses are the current position information of all satellites that each satellite can connect to, and the laser connection information table is continuously updated as the satellite position changes. The satellite logical address in the laser connection information table is used to find the satellites in front and behind each satellite and the satellites in the adjacent orbit, so as to complete the connection initialization of each satellite, and the initial cost of each link is equal; based on the connection status of each link after initialization, the traditional Dijkstra algorithm is used to plan the routes for the current communication requests, obtain the traffic status of each intersatellite link, calculate the cost of each link, define DFN[U] as the sequence number (timestamp) of the deep search of node U, LOW[U] is the minimum sequence number that can be found by U or U subtree, and the algorithm starts the depth-first search in the order of node input. The derivation conditions are: ① Every time a new node X is found, DFN[X] = LOW[X]; ② When node Y is connected to node Z, if Z is not in the stack when the time is DFN[Y], LOW[Y] = min(LOW[Y], LOW[Z]); ③ When node Y and node Z are not in the stack, LOW[Y] = min(LOW[Y], DFN[Z]); select important links and create directed traffic based on important links.

[0034] Step 200, set the link cost threshold, compare the cost of each link with the threshold, if it is greater than the threshold, it is judged as an important link, add all important links to the directed graph, and small traffic services do not need to be included in the directed graph; use the strong connectivity algorithm for the traffic directed graph created by the important links, calculate the strongly connected components of the directed graph, any pair of satellite nodes in the strongly connected components of the entire star network can be connected, and plan each obtained strongly connected component as a parallel subnet, and shrink the subnet into a node of the directed graph by shrinking the graph. In this way, route replanning is carried out, and the original routing method is used for the services in each subnet, and the cost of each link in the subnet is calculated; for cross-subnet services, long-distance links are used, and the satellite nodes in the two subnets are connected across long distances.

[0035] Step 300, each satellite-scheduled data service has specific requirements for latency, bandwidth, jitter, and VLAN tags. For these data packets with transmission requirement information, when performing cross-subnet transmission, in order to meet the transmission requirements of time-sensitive services, the data packets in the node buffer queue need to be adjusted according to their service priority. According to the VLAN tag, the VLAN tag priority of all services stored in the sending port is determined, which is generally set to 0-7.

[0036] Step 400, these data packets are sorted according to the label priority. The higher the priority, the earlier they are sent. For data packets with the same priority, a weighted priority algorithm is used to sort them for the second time. The basic principle is a linear weighted method, which evaluates the priority of the key parameters carried by the data packets on the transmission. Assume that at time t, the data packets in the cache queue of congested node i are S with different priorities. 1 ,S 2 ,…,S n , which has been arranged by label priority, assuming that S n , S n-1 , S n-2 The present invention considers several factors that have a greater impact on the transmission of time-sensitive service data packets: transmission delay constraint D, transmission bandwidth constraint B and transmission distance constraint J, e i is the influencing factor. The subdivision priority formula of the weighted priority ranking algorithm is:

[0037] P t =e 1 ·D+e 2 ·B+e 3 ·J.

[0038] Define two thresholds η 1 and η 2 , η 1 To send the threshold as quickly as possible, η 2 It is the congestion retransmission threshold. Generally, the threshold priority standard is:

[0039] η 1 =4; η 1 =2.

[0040] After adjusting the position of the services in the cache queue, the low-priority services located after the congestion retransmission threshold are discarded, and a message is sent to notify the discarded low-priority service source node to re-select a route for it. The high-priority time-sensitive services located before the as soon as possible transmission threshold are ready for span transmission. For high-priority time-sensitive services, the periodic cyclic scheduling and forwarding mechanism is used to forward them.

[0041] Step 500, the satellite physical layer responsible for the forwarding function also includes a TSN switch SW capable of assuming the function of transmitting time-sensitive services. The characteristics of SW are used to perform gated scheduling based on odd-even time periods and with time protection periods for the transmission of time-sensitive services. The timer module in SW is used to control the opening and closing of the transmission gate of the forwarding port. The present invention uses the R of the SW forwarding port to 7 Queues and Q 6 The queue with the highest priority is used to transmit time-sensitive services. Assume that the timer is set to T0 The time starts, and the Q in SW 7 The number queue is opened to transmit data and closed to write data. 6 The queue is opened to write data and closed to transmit data. After a period of time d, the timer module reaches the threshold T 0 +d, this time flips the status of the two queues, Q 7 The queue is opened to write data and closed to send data. 6 The number queue is closed for writing data and opened for transmitting data. Considering that in some cases, TSN data packets may be transmitted after the secondary priority services, the secondary priority data packets are too large, which will lead to the failure to meet the transmission delay requirements of time-sensitive services and even cause congestion of time-sensitive services. In view of this situation, the present invention extends the time period d before the time period of time-sensitive services to be transmitted. 0ffset (usually the transmission time of a standard Ethernet frame), no secondary priority services can be transmitted during this time period. Therefore, the time formula for the transmission gate opening and closing is:

[0042] T c =T 0 +d+d offset .

[0043] After introducing the parallel subnet structure, weighted priority arrangement algorithm and odd-even gated cyclic queuing forwarding mechanism, the present invention realizes the controllable delay of long-distance transmission between time-sensitive service subnets. First, when the time-sensitive service data packets and the secondary priority data packets arrive at the transmission port of the subnet transmission satellite, the time cost of arranging these data packets is D S The delay of periodic queuing forwarding at the transmission port is D in the worst case. Q =2d+d offset , jitter is 0 to 2d+d offset When the transmission is performed over a long distance via a parallel subnet, the transmission delay D can be calculated using the laser transmission information table. T Therefore, we can derive the controllable delay formula for span transmission as:

[0044] D Total =D S +D Q +D T .

[0045] Step 600, re-planning routing according to traffic to achieve cross-distance transmission of time-sensitive services.

[0046] The method of the present invention will be described below with reference to specific embodiments.

[0047] According to step 100 and step 200, it is assumed that there are currently communication requests between 12 satellites, and 14 satellites are numbered AL. According to step 100, each satellite has a laser connection information table. For example, for satellite A, it is assumed that the laser of satellite A can connect to satellite BK, but cannot connect to satellite LN. The current satellite connected to satellite A is satellite B, and the satellite IP and position logical address within the reach of the laser at the current moment record satellite BK. The connection information table will be continuously updated with the movement of the satellite. At the same time, a simple satellite network based on a laser link has completed the initialization, and the result is as follows: Figure 2 (a) As shown. After re-planning the route and constructing the subnet according to the strong connectivity algorithm, the satellite network structure is as follows Figure 2 (b) as shown.

[0048] According to step 300, assuming that many data packets are transmitted from satellite B to satellite M, in order to meet the transmission requirements of time-sensitive services, it is necessary to use satellite B and satellite I to transmit data across the network through parallel subnets. Each satellite-scheduled data service has specific requirements for latency, bandwidth, jitter, and VLAN tags. For these data packets with transmission requirement information, when performing cross-subnet transmission, in order to meet the transmission requirements of time-sensitive services, the data packets in the node buffer queue need to be adjusted according to their service priority.

[0049] According to step 400, these data packets are first sorted according to the label priority, and the higher the priority, the earlier it is sent. For data packets with the same priority, a weighted priority algorithm is used to sort the data packets with the same priority for the second time. Its basic principle is a linear weighted method, which evaluates the priority of the key parameters carried by the data packet on the transmission. Define two thresholds η 1 and η 2 , η 1 To send the threshold as quickly as possible, η 1 is the congestion retransmission threshold. After the position of the services in the cache queue is adjusted, the low-priority services behind the congestion retransmission threshold are discarded, and a message is sent to notify the discarded low-priority service source node to re-select a route for it. The high-priority time-sensitive services before the as soon as possible transmission threshold are ready for span transmission. For high-priority time-sensitive services, periodic cyclic scheduling and forwarding mechanism is used to forward them. The priority-based service scheduling and forwarding process is as follows: Figure 3 shown.

[0050] According to step 500, the characteristics of SW are used to perform gating scheduling based on odd-even time period rotation and with time protection period for the transmission of time-sensitive services. The timer module in SW is used to open and close the transmission gate of the forwarding port. The present invention adopts the R of the SW forwarding port 7 Queue and R6 The queue with the highest priority is used to transmit time-sensitive services. Assume that the timer is set to T 0 The time starts counting, and the R in SW 7 The queue is opened to transmit data and closed to write data. 6 The queue is opened to write data and closed to transmit data. After a period of time d, the timer module reaches the threshold T 0 +d, this time flips the status of the two queues, Q 7 The queue is opened to write data and closed to send data. 6 The number queue is closed for writing data and opened for transmitting data. Considering that in some cases, TSN data packets may be transmitted after the secondary priority services, the secondary priority data packets are too large, which will lead to the failure to meet the transmission delay requirements of time-sensitive services and even cause congestion of time-sensitive services. In view of this situation, the present invention extends the time period d before the time period of time-sensitive services to be transmitted. offset (usually the transmission time of a standard Ethernet frame), no secondary priority services can be transmitted during this time period. Therefore, the time point when the transmission gate is opened and closed becomes T 0 +d+d offset The switching process and timeline of gate scheduling are as follows: Figure 4 shown.

[0051] According to step 600, satellite B is selected to connect to satellite I in subnet ⑦ across a distance, and then satellite I is routed to satellite M, thereby realizing inter-satellite cross-distance connection, reducing the multi-hop delay of data from subnet ③ to subnet ⑤ and then to subnet ⑦, and ensuring efficient inter-regional transmission.

[0052] Finally, the total delay of all the "send-forward-receive" processes from the subnet output and input ports is calculated. First, the time complexity of the linear weighted priority algorithm in the present invention is n log n. S It is about several hundred microseconds, which is determined by the number of packets in the buffer. Secondly, calculate the delay in the gated scheduling. Take the worst case as the maximum delay plus the maximum jitter. Assuming that the time slot of a gated switching is 200us and the transmission time of a standard Ethernet frame is 12.44us, then the delay D of this transmission process is Q Finally, based on the transmission delay of the parallel subnet structure, assuming that there are 1500 satellites in a constellation, in the worst case, the transmission delay D T The maximum is 80ms. Therefore, according to D Total =D S +D Q +D TIt can be concluded that the total delay is 81.824ms, which not only achieves controllable delay but also meets the low delay requirements of general time-sensitive services.

[0053] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for span transmission of time-sensitive services of a low-orbit constellation, characterized in that: The following steps are involved: Obtain each satellite IP address and laser connection information table; According to the laser connection information table, each satellite node initializes the connection with adjacent satellites and plans the route according to the traditional path algorithm. After screening the initial important links by the set threshold, it shrinks the map according to the traffic weight and strong connectivity algorithm, and divides the entire satellite constellation into several parallel subnets. Traffic is routed in the constructed parallel subnets, and each packet includes basic information required for transmission and characteristics related to priority sorting; Firstly, the VLAN tag added by the source node to the data packet frame header during traffic transmission is roughly classified, and then the weighted priority scheduling algorithm is used to quickly sort the priorities. The periodic forwarding mechanism in the 802.1Qch protocol is used to output high-priority time-sensitive services through two controllable gates that are periodically opened and closed; Finally, the route is re-planned according to the traffic volume to achieve long-distance connection and predictable transmission delay for time-sensitive services.

2. A method for transmitting time-sensitive services over a low-orbit constellation span as claimed in claim 1, characterized in that: Each satellite has a laser connection information table, which records the satellites to which each satellite is currently connected, the satellite IPs within the laser reachable range at the current moment, and their position logical addresses; wherein, the satellite IPs within the laser reachable range are the satellite IPs to which each satellite can adjust its laser for connection, and the position logical addresses are the current position information of all satellites to which each satellite can connect, and the laser connection information table is continuously updated as the satellite position changes.

3. A method for transmitting time-sensitive services across low-orbit constellation distances as claimed in claim 2, characterized in that: The satellite logical addresses in the laser connection information table are used to find the satellites in front and behind each satellite in the same orbit and the left and right satellites in the adjacent orbit, so as to complete the connection initialization of each satellite, and the initial cost of each link is equal; based on the connection status of each link after initialization, the traditional Dijkstra algorithm is used to plan routes for various current communication requests, obtain the traffic status of each inter-satellite link, and calculate the cost of each link; select important links and create directed traffic based on important links.

4. The method for transmitting time-sensitive services of a low-orbit constellation across a distance as claimed in claim 3, characterized in that: Traffic routing is performed in the constructed multiple parallel subnets, and the traffic is simulated traffic for real-life communication needs and large-scale satellite constellation routing.

5. A method for transmitting time-sensitive services across low-orbit constellation distances as claimed in claim 4, characterized in that: Each satellite-scheduled data service has specific requirements for latency, bandwidth, jitter, and VLAN tags.

6. A method for transmitting time-sensitive services across low-orbit constellation distances as claimed in claim 5, characterized in that: For data packets with transmission requirement information, when performing cross-distance transmission between subnets, the positions of the data packets in the node buffer queue need to be adjusted according to their service priorities.

7. A method for transmitting time-sensitive services over a low-orbit constellation span as claimed in claim 6, characterized in that: First, according to the VLAN tag, determine the VLAN tag priority of all services stored in the sending port, which is generally set to 0-7; sort the data packets according to the tag priority first, and the higher the priority, the earlier they are sent; for data packets with the same priority, use the weighted priority algorithm to sort them for the second time; assume that the data packets in the cache queue of congested node i at time t are S1, S2, ..., S n , which has been arranged by label priority, assuming that S n , S n-1 , S n-2 The label priority of the time-sensitive service data packet is the same; the factors affecting the transmission of the time-sensitive service data packet include the transmission delay constraint D, the transmission bandwidth constraint B and the transmission distance constraint J, e i is the impact factor, where the formula of the weighted priority ranking algorithm is: S nt =e1·D+e2·B+e3·J。 8. A method for transmitting time-sensitive services over a low-orbit constellation span as claimed in claim 7, characterized in that: Two thresholds η1 and η2 are defined, η1 is the threshold for sending as soon as possible, and η2 is the congestion retransmission threshold. After adjusting the position of the services in the cache queue, the low-priority services located after the congestion retransmission threshold are discarded, and a message is sent to notify the discarded low-priority service source node to reselect a route for it, and the high-priority time-sensitive services located before the threshold for sending as soon as possible are prepared for span transmission; for high-priority time-sensitive services, a periodic cyclic scheduling and forwarding mechanism is used to schedule their forwarding.

9. A method for transmitting time-sensitive services over a low-orbit constellation span as claimed in claim 8, characterized in that: The satellite physical layer responsible for the forwarding function also includes a TSN switch SW that can undertake the transmission function of time-sensitive services. Utilizing the characteristics of SW, gating scheduling based on odd-even time periods and with time protection periods is performed for the transmission of time-sensitive services.

10. A method for transmitting time-sensitive services over a low-orbit constellation span as claimed in claim 9, characterized in that: The timer module in SW is used to regulate the opening and closing of the transmission gate of the forwarding port. Specifically, the Q7 queue and Q6 queue of the SW forwarding port are used to transmit the time-sensitive service with the highest priority. Assume that the timer starts at time T0, at this time, the Q7 queue in SW turns on the transmission data and turns off the writing data, and the Q6 queue turns on the writing data and turns off the transmission data. After a period of time d, the timer module reaches the threshold T0+d, at which time the states of the two queues are flipped, the Q7 queue turns on the writing data and turns off the sending data, and the Q6 queue turns off the writing data and turns on the transmission data. Extend the time before the transmission of time-sensitive services by a short period of time offset , which is generally the transmission time of a standard Ethernet frame. No secondary priority services can be transmitted during this time period. At this time, the time point when the transmission gate is opened and closed becomes T0+d+d offset .

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