CN102201988A - Scheduling method of avionics full duplex switched Ethernet (AFDX) exchanger - Google Patents

Abstract

The invention discloses a scheduling method for an avionics full-duplex switched Ethernet switch. The message to be sent is encapsulated into a standard Ethernet frame format and filtered, and the filtered message is sent to the output of the AFDX switch according to the routing configuration table. Buffer and establish a virtual output queue VQQ, calculate the urgency of each message in VQQ and set the initial priority, and send information in the order of priority. The invention effectively reduces the delay time of high-priority messages and improves the service quality of the AFDX network.

Description

A scheduling method for an avionics full-duplex switched Ethernet switch

technical field

The invention relates to a scheduling method for an Ethernet switch.

Background technique

Avionics full-duplex switched Ethernet (AFDX) is evolved on the basis of commercial Ethernet. It adds a "deterministic network" real-time guarantee mechanism and dual redundancy management to traditional Ethernet. The reliability mechanism to meet the needs of modern avionics has become a new generation of avionics system bus.

For the aircraft network, each network transmission request must be served, and the end-to-end delay of each transmission must be guaranteed, which involves the reasonable and efficient scheduling of messages between avionics systems. In the process of message transmission between AFDX end systems, a suitable one-way virtual link (VL) is first defined for message transmission, and the message is encapsulated into a standard Ethernet frame format through UDP header, IP header, and Ethernet frame header in turn , through traffic regulation and scheduling strategies, make it a frame that meets the requirements of the VL, the message frame is sent to the output port of the source end system, and then sent to the AFDX dual-redundancy switching network, and the AFDX switch receives the message to be transmitted After framing, the filtering and control module in the switch first filters the message frames from each end system in terms of integrity, frame length, traffic budget, and acceptable destination addresses, and discards frames that do not meet the requirements. To the frames that meet the requirements, enter the switching function module of the switch, search the destination address (virtual link identifier) of the message frame according to the configuration table, then schedule the message frames waiting in the buffer area, and determine the sequence of message frame output, The frame is forwarded to the appropriate physical port, the message frame is output to the destination port through the output port of the switch, and the destination end system performs integrity detection on the received message frame and then processes the message frame. This is a complete transmission process of a message frame.

At present, the research on the AFDX network scheduling algorithm mainly focuses on the VL scheduling of the peer system, and the quality of the AFDX switch is an important indicator that affects the performance of the AFDX network. When the switching function module of the AFDX switch processes message frames, different scheduling algorithms adopted by the switch will cause differences in the forwarding delay of message frames. The current scheduling of switches mainly adopts round-robin scheduling algorithm, which can make messages evenly served. However, in avionics systems, there are often some messages with high urgency that need to be served immediately, and the equality of round-robin algorithm cannot be achieved. Satisfy scheduling needs for urgent messages.

Contents of the invention

In order to overcome the deficiency that the existing technology cannot meet the emergency message dispatching requirements, the present invention provides an avionics full-duplex switched Ethernet switch dispatching method, according to the different deadlines of each message frame, priority is given to sending emergency messages with smaller deadlines , so that urgent messages can be served immediately when they need to be transmitted, reducing delay time. Sending messages according to different deadlines of message frames can not only ensure that each message is served before its own deadline, but also meet the requirements of messages with higher urgency, and effectively reduce the number of messages with higher urgency in AFDX The transmission delay in the network improves the service quality of the entire avionics network for message processing.

The technical solution adopted by the present invention to solve the technical problem is that after the message enters the buffer queue at the input end of the switch, different priorities are given to the message according to the deadline of the message frame, and the highest priority is given to the message frame with the earliest deadline. Make it get served as early as possible, and reduce the delay time of its transmission in the network. Specifically include the following steps:

Step 1. The source end system encapsulates the message to be sent into a standard Ethernet frame format, and sends it to the VL for transmission.

Step 2: After transmitting the message obtained in step 1 to the switching network of AFDX, the AFDX switchboard filters the incoming message, discards it if it does not meet the requirements of the AFDX frame, and proceeds to the next step if it meets the requirements.

Step 3: Send the received message to the output buffer of the AFDX switch according to the routing configuration table.

Step 4: Create a virtual output queue (VQQ) for the message to be sent, queue up and wait for forwarding.

Step five, calculate the urgency of each message in the VQQ, and set the initial priority for the message according to the deadline when the message enters the VQQ, specifically including the following steps:

1: In each VQQ, set a counter to calculate the deadline d _i (t)-t of each message entering the VQQ, where d _i (t) is the task time limit of the message, which is determined by the source system that sends the message , t is the current time.

2: Compare the cut-off time of each message in the current queue, and set the initial priority for new messages. The message with a shorter cut-off time has a higher initial priority.

Step 6. If the message currently entering the VQQ has the shortest deadline, that is, the initial priority is the highest, forward the message to the physical port to complete the forwarding of the message. If the cut-off time of the message currently entering the VQQ is not the shortest, that is, the initial priority is low, then enter the next step.

Step 7. The message continues to wait in the VQQ, and after every specified time period, the priority of all the messages in the VQQ is increased by one, and the message with the highest priority is selected to be sent each time.

Step 8. Whenever there is a new message from VQQ, go to step 5.

The beneficial effects of the present invention are: in the message transmission of the AFDX network, by adopting the dynamic earliest deadline first scheduling algorithm (EDF) for the AFDX switch, the switch can send messages with higher urgency first, effectively reducing the number of high-priority messages. The delay time of the message improves the service quality of the AFDX network.

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is the flow chart of the implementation of the EDF scheduling algorithm in the AFDX switch.

Detailed ways

Messages are transported between the two end systems over virtual links. Considering that an end system A (source end system) needs to send a message E to end system B (destination end system), it is assumed that the virtual link whose ID number is 10 of the VL transmits the message.

Step 1. End system A encapsulates the message frame and schedules it to meet the requirements of VLID10, and sends message E to VLID10 for transmission.

Step 2: The message E is sent to the AFDX switching network, assuming that the message E is a frame meeting the requirements.

Step 3: The message E enters the Rx buffer of the switch, and the output buffer of the message is determined according to the configuration table.

Step 4: Determine the VQQ from input to output of message E.

Step 5: The counter in the VQQ calculates the deadline of the message E, and gives the message E an initial priority.

Assume that there are 4 messages waiting to be sent in the VQQ queue at this time, and the deadlines (d _i (t)-t) are:

information Deadline (ms) A 0.07 B 0.03 C 0.02 D 0.04

Step six, two situations:

1: Assume that the deadline for incoming message E is 0.01ms.

Then the priorities of the five messages in VQQ are set to: (Priority 1 is the highest)

information Deadline (ms) priority A 0.07 5 B 0.03 3 C 0.02 2 D 0.04 4 E 0.01 1

At this time, the new message E in the queue has the highest initial priority, indicating that the message E in the queue has the highest urgency at this time, and the message E is forwarded to the corresponding output port. Complete the transmission of message E in the switch.

2: Assume that the deadline for incoming message E is 0.05ms.

Then the priorities of the five messages in VQQ are set to:

information Deadline (ms) priority A 0.07 5 B 0.03 2 C 0.02 1 D 0.04 3 E 0.05 4

Step 7. At this time, the message C in the VQQ queue has the highest priority and is transmitted first, while the new message E and the other three messages in the queue continue to wait, and the priority of the message after a time slice (assumed to be 0.01ms) The dynamic update is:

information Deadline (ms) priority A 0.06 4 B 0.02 1 D 0.03 2 E 0.04 3

At this time, message B has the highest priority and is transmitted first. Then after a time slice, the priority is updated again until the priority of message E is updated to the highest, and then message E is output.

Step 8. If a new message F enters the VQQ queue when the priority of the message E is not updated to the highest, repeat step 5.

Claims (1)

1. an avionic full-duplex switched-type Ethernet switch dispatching method is characterized in that comprising the steps:

The message that step 1, source end system will send is packaged into the ethernet frame format of standard, and it is first-class to be transmitted to send to VL;

Step 2, transmission of messages that step 1 is obtained are behind the switching network of AFDX, and the AFDX switch filters the message that arrives, if not satisfying the requirement of AFDX frame does not then abandon, meets the demands and continues next step;

Step 3, according to the routing configuration table, the message that receives is sent to the output buffer of AFDX switch;

Step 4, set up a virtual output queue VQQ, wait in line to transmit for the message that will send;

Step 5, calculate the pressing degree of the message among each bar VQQ, and the deadline when entering VQQ message be provided with initial priority, specifically may further comprise the steps according to message:

1) in each VQQ, a counter is set, calculate d deadline of each message that enters VQQ _i(t)-and t, d _i(t) be the task time limit of this message, by the source end system decision that sends message, t is the current time;

2) size deadline of each message in the current queue relatively is provided with initial priority to new information, and deadline, more little message initial priority was high more;

Step 6, the shortest deadline if work as the message that advances into VQQ, promptly initial priority is the highest, then transmits the physical port that this message arrives, and finishes the forwarding to message; If when the message that advance into VQQ be not deadline the shortest be that initial priority is lower, then enter next step;

Step 7, message continue wait in VQQ, and after the time period of an appointment, all message priorities among the VQQ are added one, select the highest message of priority to send at every turn;

Step 8, when VQQ has new information to arrive, enter step 5.

Images