CN102201988A

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

Info

Publication number: CN102201988A
Application number: CN2011101232500A
Authority: CN
Inventors: 李杜娟; 张建东; 史国庆; 吴勇; 时洋洋
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2011-05-12
Filing date: 2011-05-12
Publication date: 2011-09-28

Abstract

The invention discloses a scheduling method of an avionics full duplex switched Ethernet (AFDX) exchanger. The method comprises the following steps of: encapsulating a message to be sent into a message of a standard Ethernet format and filtering; sending the filtered message to an output buffer area of the AFDX exchanger according to a route configuration table and establishing a virtual output queue (VQQ); calculating the urgency degree of each VQQ message and setting an initial priority; and sequentially sending messages according to priorities. By adopting the scheduling method, the delay time of high-priority messages is reduced effectively, and the service quality of an AFDX network is enhanced.

Description

A kind of avionic full-duplex switched-type Ethernet switch dispatching method

Technical field

The present invention relates to a kind of Ethernet switch dispatching method.

Background technology

Avionic full-duplex switched-type Ethernet (AFDX) is to develop on the basis of commercial Ethernet and come, it has increased " deterministic network " on the basis of traditional ethernet real-time guarantees that the reliability mechanisms of mechanism, two Redundancy Managements satisfies modern avionic demand, becomes the avionics system bus of a new generation.

For aircraft network, each Network Transmission request must obtain service, and must guarantee the end-to-end time delay of each transmission, this just relate between each system of aviation electronics message rationally, scheduling problem efficiently.In the message transmitting procedure between the AFDX end system, it at first is a transmission definition suitable unidirectional virtual link (VL) of message, message is passed through the UDP head successively, the IP head, the Ethernet frame head is encapsulated into the ethernet frame format of standard, regular by flow, scheduling strategy, it is become satisfy the frame that this VL requires, message frame is sent to the output port of source end system, be sent to the switching network of the two remainings of AFDX then, after the AFDX switch receives the message frame that will transmit, at first by the filtration in the switch and control module to from the message frame of each end system in integrality, frame length, filter aspects such as flow budget and acceptable destination address, abandons undesirable frame.To satisfactory frame, enter the function of exchange module of switch, search the destination address (virtual link identifier) of message frame according to allocation list, the message frame that this buffer area is waited for is dispatched then, determine the sequencing of message frame output, frame is forwarded to suitable physical port, message frame is by the switch output port, output to destination interface, the message frame that the destination system docking is received carries out integrity detection reprocessing message frame.This is a transmission course that message frame is complete.

Research to AFDX network scheduling algorithm at present mainly concentrates on peer-to-peer system VL scheduling aspect, and the quality of AFDX switch is an important indicator that influences the AFDX network performance.During the function of exchange resume module message frame of AFDX switch, the forward delay that the different dispatching algorithms that switch adopts can make message frame is difference to some extent.The polling dispatching algorithm is mainly adopted in the scheduling of present switch, this method can make the service that obtains of message equalization, but often have the higher message of some urgency in the avionics system and need obtain service immediately, the isotropism of polling algorithm just can not satisfy the dispatching requirement to emergency message.

Summary of the invention

In order to overcome the deficiency that prior art can not satisfy the emergency message dispatching requirement, the invention provides a kind of avionic full-duplex switched-type Ethernet switch dispatching method, according to the different deadlines of each message frame, preferential less emergency message deadline that sends, make emergency message can when needs transmit, obtain service immediately, reduce time of delay.According to sending different deadlines of message frame message, can guarantee that not only each message obtained service before the deadline of itself, and be well positioned to meet the higher message requirement of urgency, can effectively reduce the propagation delay time of the higher message of urgency in the AFDX network, improve the service quality of whole avionics network Message Processing.

The technical solution adopted for the present invention to solve the technical problems is after message enters the buffer queue of switch input, according to the deadline of message frame, give different priority to message, to deadline message frame the earliest give the highest priority, make its service that obtains as far as possible early, reduce its transmission delay time in network.Specifically may further comprise 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, calculates 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, new information is provided with initial priority, 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.

The invention has the beneficial effects as follows: in the transmission of messages of AFDX network, by the AFDX switch being adopted dynamically the earliest the deadline of dispatching algorithm (EDF) at first, make switch preferentially send the higher message of urgency, effectively reduce the time of delay of high-priority message, improved the service quality of AFDX network.

The present invention is further described below in conjunction with drawings and Examples.

Description of drawings

Fig. 1 is the implementing procedure figure of EDF dispatching algorithm in the AFDX switch.

Embodiment

Message is transmitted in two end systems by virtual link.Consider that an end system A (source end system) need to send message E to end system B (destination system), ID number of supposing VL is that 10 virtual link transmits this message.

Step 1, the packaged message frame of end system A also regularly are scheduling to the requirement of satisfying VLID10 with it, and it is first-class to be transmitted that message E is sent to VLID10.

Step 2, message E are sent to the AFDX switching network, suppose that message E is satisfactory frame.

Step 3, message E enter switch rx buffering district, according to allocation list, determine the output buffer of message.

Step 4, determine that message E is input to the VQQ of output.

Counter among step 5, this VQQ calculates the deadline of message E, and gives message E initial priority.

Suppose to have in this VQQ formation this moment 4 message to send waiting in line, deadline (d _i(t)-t) be respectively:

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

Step 6, two kinds of situations:

1: what suppose newly to advance message E is 0.01ms by the time.

The priority of 5 message among VQQ this moment just is set to so: (priority 1 is the highest)

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

Then the initial E priority of the message of newly advancing in formation this moment is the highest, illustrates that the message E urgency in formation this moment is the highest, then transmits message E to corresponding output port.Finish the transmission of message E in switch.

2: what suppose newly to advance message E is 0.05ms by the time.

The priority of 5 message among VQQ this moment just is set to so:

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

Message C priority in step 7, VQQ formation this moment is the highest, obtains transmission at first, and the message of its excess-three in new information E and the formation continues to wait for, after a timeslice (being assumed to be 0.01ms) priority of message dynamically update into:

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

This moment, message B priority was the highest, transmission at first.After a timeslice, upgrade priority once more then, until the priority update of message E when the highest, output message E again.

Step 8, if be not updated to when the highest in message E priority, have new information F to enter this VQQ formation again, then repeating step five.

Claims

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;

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.