CN111092712B

CN111092712B - Preemptive scheduling method for time-triggered Ethernet

Info

Publication number: CN111092712B
Application number: CN201911192136.6A
Authority: CN
Inventors: 孔维刚; 张志平; 刘智武; 逯计划; 周耿; 王晨博
Original assignee: Xian Aeronautics Computing Technique Research Institute of AVIC
Current assignee: Xian Aeronautics Computing Technique Research Institute of AVIC
Priority date: 2019-11-28
Filing date: 2019-11-28
Publication date: 2022-04-05
Anticipated expiration: 2039-11-28
Also published as: CN111092712A

Abstract

The invention belongs to the technical field of network communication, and particularly relates to a preemptive scheduling method for time-triggered Ethernet, which solves the risk problem that interrupted ET messages may pass through frame verification at a receiving end. The invention can reduce the transmission jitter of TT message, ensure the reliable transmission of ET message, and enlarge the application range of the preemptive dispatching method of time-triggered Ethernet by adopting the method of constructing invalid frame check sequence.

Description

Preemptive scheduling method for time-triggered Ethernet

Technical Field

The invention belongs to the technical field of network communication, and relates to a preemptive scheduling method for time-triggered Ethernet.

Background

Time triggered ethernet may implement a hybrid communication of time triggered TT messages, event triggered ET messages (rate limited RC messages or, as far as possible, BE messages) on a unified network architecture.

Considering contention of TT message and ET message data traffic on network link resources, the scheduling policy directly affects the system performance of the time triggered Ethernet. The following scheduling methods are currently included: a priority scheduling method, a reserved time period scheduling method and a preemptive scheduling method. The priority scheduling method enables TT messages to have large jitter, and system performance is affected. The reserved time period scheduling method may cause a problem of bandwidth waste or complex implementation. The preemptive scheduling method has the advantages of small TT message jitter and high network bandwidth utilization rate, but has the risk problem that a receiver only receives fragment data of an ET message and frame check is possible, and the use range is limited.

Disclosure of Invention

The invention provides a preemptive scheduling method for time-triggered Ethernet, which can reduce the transmission jitter of TT messages and solve the risk problem that interrupted ET messages may pass through frame verification at a receiving end by adopting a method of constructing an invalid frame verification sequence.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a preemptive scheduling method for time-triggered Ethernet comprises the following steps:

step 1, sending TT messages at predefined sending moments of a TT message sending schedule, wherein the predefined sending moments are called preemption moments, and if no ET message is sent, the TT messages are normally sent; otherwise, executing step 2;

step 2, judging the length of an ET message segment sent out before the preemption time, and if the length of the ET message segment sent out before the preemption time is less than 64 bytes, executing step 3; if the length of the ET message fragment sent before the preemption moment is more than or equal to 64 bytes and is less than (frame length-1) bytes of the ET message, executing the step 4; if the length of the ET message fragment sent before the preemption moment is equal to the (frame length-1) byte of the ET message, executing the step 6;

step 3, interrupting the ET message being sent, and sending a TT message at the preemption moment;

step 4, before the preemption moment, forming FCS1 by 4 bytes of data sent by the ET message at last, judging whether FCS1 is equal to the check value of the frame content between the 1 st byte and the 5 th byte before the preemption moment of the sent ET message segment, if so, executing step 5, and if not, sending TT message at the preemption moment;

step 5, sending out a 1-byte construction data after the preemption moment, and sending the preempted TT message after sending out the 1-byte construction data; the 1-byte construction data construction process comprises the following steps: 1-byte construction data is placed after 3-byte data sent out at the end of an ET message segment, and a 4-byte data FCS2 is reconstructed, so that FCS2 is not equal to a check value of frame contents between the 1 st byte of the sent-out ET message segment and the 4 th reciprocal byte before the preemption moment;

and 6, reserving 1 byte data time after the preemption moment, and sending the preempted TT message after completely sending out the last byte data of the ET message.

Further, in step 1, the ET message includes an RC message or a BE message.

Compared with the prior art, the technical scheme of the invention has the beneficial effects that:

the method can solve the risk problem that the interrupted ET message segment can pass through the frame verification at the receiving end in the preemptive scheduling method of the time-triggered Ethernet, ensure the reliable transmission of the ET message and enlarge the application range of the preemptive scheduling method of the time-triggered Ethernet.

Drawings

FIG. 1 is a scenario 1 in which a TT message preempts an ET message in the method of the present invention;

FIG. 2 is a scenario 2 of the TT message preempting the ET message in the method of the present invention;

fig. 3 is a TT message preemption ET message scenario 3 in the method of the present invention.

Detailed Description

Embodiments of the present invention are further described below with reference to the accompanying drawings.

In the process of time-triggered Ethernet scheduling, the preemptive scheduling method is used, so that the advantages of reducing TT message transmission jitter and increasing the network bandwidth utilization rate are achieved, but the risk problem that ET message (RC message or BE message) segments interrupted by TT messages may pass through frame check and check of a receiving party exists, and the application range of the preemptive scheduling method is limited. The invention provides a preemptive scheduling method for time-triggered Ethernet, which can reduce the transmission jitter of TT messages by adopting a method for constructing an invalid frame check sequence, solve the risk problem that interrupted ET messages can pass through frame check at a receiving end and ensure the reliable transmission of the ET messages.

According to the time triggered Ethernet standard, the frame structures of TT message and ET message adopt the common Ethernet frame structure, and are distinguished by the Ethernet frame type field. When a TT message is transmitted at a transmission time (called a preemption time) predefined by the TT message transmission schedule, there are four cases:

1) no ET message is in transmission; 2) the length of the sent ET message segment is less than 64 bytes; 3) the length of the sent ET message segment is greater than or equal to 64 bytes and smaller than (frame length-1) bytes of the ET message; 4) the length of the transmitted ET message segment is equal to (frame length-1) bytes of the ET message.

Aiming at the four situations, a scheduling method is respectively designed:

1) normally sending TT information at the preemption moment;

2) interrupting the ET message being sent, and sending a TT message at the preemption moment;

3) judging whether an FCS1 formed by 4 bytes of data sent by the ET message before the preemption time is equal to a check value of frame contents between the 1 st byte of an sent ET message fragment and the 5 th reciprocal byte before the preemption time, if so, sending a 1-byte construction data after the preemption time, wherein the principle of the 1-byte construction data is as follows: after the last 3 bytes of data sent out by the ET message segment, a 4-byte data FCS2 is reconstructed, so that FCS2 is not equal to the check value of the frame content between the 1 st byte and the 4 th byte before the preemption moment of the sent out ET message segment; after the 1 byte construction data is sent, sending the occupied TT message;

4) and reserving 1 byte data time after the preemption moment, and sending the preempted TT message after completely sending out the last byte data of the ET message.

Based on the above description, the present invention provides a preemptive scheduling method for time-triggered ethernet, which comprises the following detailed steps:

step 1, when TT information is sent at the sending time (called as preemption time) predefined by a TT information sending schedule, if no ET information is in sending, the TT information is normally sent; otherwise, executing step 2;

step 2, judging the length of an ET message segment sent out before the preemption time, and if the length of the ET message segment sent out before the preemption time is less than 64 bytes, executing step 3 as shown in figure 1; if the length of the ET message fragment sent before the preemption moment is greater than or equal to 64 bytes and smaller than (frame length-1) bytes of the ET message, as shown in fig. 2, executing step 4; if the length of the ET message fragment sent before the preemption moment is equal to (frame length-1) bytes of the ET message, as shown in FIG. 3, executing step 6;

step 3, as shown in fig. 1, interrupting the ET message being sent, and sending a TT message at the preemption time T3;

step 4, as shown in fig. 2, determining whether an FCS1 composed of 4 bytes of data (i.e., between time T5 and time T3 in fig. 2) sent by the ET message last before the preemption time T3 is equal to a check value of a frame content between the 1 st byte of the sent ET message segment and the 5 th byte before the last preemption time (i.e., between time T1 and time T5 in fig. 2), if so, executing step 5, and if not, sending a TT message at the preemption time;

step 5, sending out a 1-byte construction data after the preemption time T3, wherein the principle of the 1-byte construction data is as follows: the 1-byte construction data is put after the last sent 3-byte data in the ET message segment (i.e. between time T6 and T3 in fig. 2), a 4-byte data FCS2 is reassembled, so that the FCS2 is not equal to the check value of the frame content between the 1 st byte of the sent ET message segment and the 4 th byte data before the preemption time (i.e. time T1 to T6 in fig. 2), and after the 1-byte construction data is sent, the preempted TT message is sent at time T4;

step 6, as shown in fig. 3, after the preemption time T3, a 1-byte data time is reserved, and after the last byte data of the ET message is completely sent out, the preempted TT message is sent at time T2.

Claims

1. A preemptive scheduling method for time-triggered Ethernet is characterized by comprising the following steps:

2. The time-triggered ethernet preemptive scheduling method according to claim 1, wherein: in step 1, the ET message includes an RC message or a BE message.