CN105162612A

CN105162612A - Method for calculating data backlog in AFDX (Avionic Full-Duplex Switched Ethernet) network

Info

Publication number: CN105162612A
Application number: CN201510336533.1A
Authority: CN
Inventors: 盛春玲; 罗海; 付佩; 缪万胜; 谷青范
Original assignee: China Aeronautical Radio Electronics Research Institute
Current assignee: China Aeronautical Radio Electronics Research Institute
Priority date: 2015-06-17
Filing date: 2015-06-17
Publication date: 2015-12-16
Anticipated expiration: 2035-06-17
Also published as: CN105162612B

Abstract

The invention discloses a method for calculating data backlog in an AFDX (Avionic Full-Duplex Switched Ethernet) network, which comprises the steps of S1, dividing the AFDX network into different subnets according to the priority, carrying out independent network analysis in allusion to each subset, and calculating an arrival curve and a service curve of each virtual link; S2, calculating data delay Di caused by queuing inside each switch; and S3, calculating data backlog of each node according to the data delay Di. Through the method disclosed by the invention, a lower data backlog upper bound in the AFDX network is acquired, thereby providing a more reliable theoretical basis and a larger configuration data optimization space for network resource distribution, and more effectively ensuring the certainty of the AFDX network.

Description

A kind of method calculating data in AFDX network and overstock

Technical field

The present invention relates to AFDX (AvionicFull-DuplexSwitchedEthernet) switch network analytical technology, particularly a kind of method calculating data in AFDX network and overstock in AFDX network deterministic parsing process.

Background technology

AFDX is the certainty airplane data networking bus system being applicable to avionics system information transmission.AFDX on Basic Ethernet, add certainty timing mechanism and reliable information transmission mechanisms is applied to adapt to avionics, certainty timing mechanism is realized by the virtual link technology with finite bandwidth and frame transmission interval, reliable information transmission is then realized by frame administrative mechanism, comprises redundant transmission and the integrity checking of information.The state of avionics system qualitative representation system is really foreseeable, namely knows that the current state of system and transition criterion just can the behaviors of Estimation System.Certainty is always correlated with safety analysis.In order to the safety of aircraft, deterministic requirement is applicable to each system level of aircraft.For data communication system, data communication must require to ensure certainty by network analysis.

Network calculus is a network certainty queuing theory, is the theoretical foundation of AFDX network deterministic parsing.The deterministic parsing of AFDX network needs Calculus Theory Network Based calculate delay, the shake of information transmission in worst case lower network and overstock.Network calculus is proposed in 1991 by L.Cruz, through the development of twenties years, especially the people such as Agrawal, LeBoudec is to the proposition of service curves, Min-plus algebra and class convolution concept, make network calculus become basis complete, be widely used, theory that system is huge.

The people such as C.Fraboul and J.Grieu are applied to AFDX network the basic theories of network calculus the earliest, propose than more complete model and algorithm.Wherein most important two parameters are exactly that data delay and data overstock.In engineering reality, the maximum data that network allows overstocks and is configured in units of frame number, therefore needs to calculate the upper bound of the frame number of the inner each priority backlog of switch in network transmission process in network analysis.Existing Mathematical Modeling and algorithm thereof are when calculated data overstocks the frame number upper bound, in units of byte, and all frames that tentation data buffering area is overstock are the maximum of the maximum frame length (MaxFrameSize) of virtual links (VL, VirtualLink) all in this priority.This computational methods are too coarse, and comparison of computational results is pessimistic, often overstocks the upper bound far beyond real data.

Summary of the invention

In order to the frame number computational methods that the data realizing more excellent AFDX network analysis modeling overstock, the invention provides a kind of method calculating data in AFDX network and overstock, obtain data lower in AFDX network and overstock the upper bound, for Resource Allocation in Networks provides more reliable theoretical foundation and larger configuration data to optimize space, more effectively ensure the certainty of AFDX network.

Goal of the invention of the present invention is achieved through the following technical solutions:

Calculate the method that in AFDX network, data overstock, comprise following steps:

Step one, AFDX network is divided into different subnets according to priority, independently carries out network analysis for each subnet, calculate the arrival curve of each virtual link in each switch internal damping exit position and service curves:

A) arrival curve of network in each subnet is calculated:

α(t)＝σ+ρt，

Wherein, be σ burstiness, ρ is transmission rate;

B) service curves of network in each subnet is calculated:

β _R,T(t)＝R[t-T] ⁺,

Wherein R is service speed, and T is service delay, symbol [x] ⁺represent: if x>=0, this value equals x, otherwise this value is 0.

Step 2, the data delay D caused due to queuing by arrival curve and service curve calculation _i, computing formula is:

D _i＝sup _t≥0{inf _τ≥0{α(t)≤β(t+τ)}}

Carry out calculated data without maximum transversal distance in step 3, the present invention and overstock the upper bound, but come the overstocked frame number upper bound of calculated data with the upper bound of data delay.According to data delay D _ithe data calculating each node overstock:

Wherein: T _{tachnical delay}for the tachnical delay upper bound of each node, general T _{tachnical delay}=50 μ s, T _shapingfor from the tachnical delay be shaped into from starting terminal to export.

Accompanying drawing explanation

Fig. 1 is embodiment neutron network topology structure;

Fig. 2 is arrival curve schematic diagram in embodiment;

Fig. 3 is service curves schematic diagram in embodiment;

Fig. 4 is data delay schematic diagram under worst case in embodiment;

Fig. 5 is schematic flow sheet of the present invention.

Embodiment

In method in the past, it is after obtaining arrival curve and service curves that data delay and data overstock, get the horizontal computation of maximal distance data delay upper bound, get longitudinal computation of maximal distance data and overstock the upper bound, it is separately parallel computation that data delay and data overstock.Carry out calculated data without maximum transversal distance in the present invention and overstock the upper bound, but come the overstocked frame number upper bound of calculated data with the upper bound of data delay.

Due in AFDX network data send periodicity, within cycle regular hour, the frame number sent out from transmitting terminal is bounded above, the present invention according to every bar VL data in a network residence time computing network or certain node data overstock.

As shown in Figure 5, implementing procedure of the present invention is as follows:

Arrival curve and service curves is asked after step one, subregion.

Network partition:

First need network to be divided into different subnets according to priority, independently carry out network analysis calculating for each subnet.Namely for multipriority AFDX network, AFDX network need be divided into multiple subnet according to priority, each subnet only comprises the VL of same priority.Fig. 1 is the network topology structure figure of certain priority subnet.Wherein i represents network node (each outlet of switch has a buffering area, and each buffering area is a network node).

Such as, there is the VL of height (H), low (L) two priority in the AFDX network of A, B net redundancy, then can be divided into four subnets:

N (H, A): comprise all high priority VL netted by A;

N (H, B): comprise all high priority VL netted by B;

N (L, A): comprise all low priority VL netted by A;

N (L, B): comprise all low priority VL netted by A;

Calculate before data overstock in subnet, need first to calculate the arrival curve of network in this subnet, service curves and data delay.

Arrival curve:

VL is as the basic data transmission channel in AFDX network, and terminal is by controlling the maximum frame length S of Frame in every bar VL _maxand send the transmission that interval BAG carrys out control information, according to the leakage prediction of shaping, the arrival curve of VL can be obtained:

α(t)＝σ+ρt

Be wherein σ burstiness, ρ is transmission rate.Arrival curve schematic diagram as shown in Figure 2.

Service curves:

A basic service curves model is called rate delay service curves, as follows:

β _R,T(t)＝R[t-T] ⁺

Service curves schematic diagram as shown in Figure 3.

Step 2, checking computations theory calculate Network Based go out the data delay of each virtual link.

By the network analysis of Calculus Theory Network Based, can calculate each VL inner due to the data delay caused of queuing up at each switch, we are designated as D this parameter _i.

Assuming that data flow to into certain buffer joint, the arrival curve of this data flow is α (t), and service curves is β (t).The then maximum data delay D of this buffer joint _i(unit: ms) is the maximum transversal distance between α (t) and β (t), as shown in Figure 4.Then there is following formula:

D _i＝sup _t≥0{inf _τ≥0{α(t)≤β(t+τ)}}。

Step 3, on the basis of data delay calculated data overstock.

1, every bar VL follows its transmission cycle, therefore timing from this point from transmitting terminal reshaper, assuming that from be shaped into from the tachnical delay starting terminal to export be T _shaping, then every bar VL _kdelay Bound before sending from transmitting terminal reshaper to certain node m for:

Illustrate:

A () set A comprises from transmitting terminal, VL _kalong its sub-path arrive node m the set (comprising node m) that forms of all nodes of process.

B () transmitting time exceedes the frame of this time not in the buffering area of node m.

(c) T _{tachnical delay}=50 μ s are the tachnical delay upper bound of each node.

2, in AFDX network, Frame periodically sends according to minimum bandwidth interval (BAG), then every bar VL _k? the frame number upper bound sent in time is:

also the data being node m are overstocked, belong to VL _kthe frame number upper bound, this result can be optimized further.

Represent from transmitting terminal by set B, VL _karrive along its sub-path the previous node of node m the set (not comprising node m) that forms of all nodes of process.

Then there is following fundamental formular:

A the data of () m point overstock=and the data of set A overstock-and the data of set B overstock;

The data that b data that the data of () m point overstock the upper bound=set A overstock the upper bound-set B overstock next

And the Frame of not all overstocks at node i place, at VL _kall nodes on path all can overstock, and the Nodes calculated below is before this minimum overstocked.

Assuming that entering node N _mnode before is not queued up, and only there is tachnical delay.Due to

Total tachnical delay within this time is less than VL _kone send the cycle, the minimum frame number that can overstock is 0.This illustrates in the time interval, on the path before node m, the lower bound that set B overstocks is 0.

Therefore, be just node N _mthat overstocks belongs to VL _kthe frame number upper bound of frame.

3, above calculating is all for a VL _k, if having multiple through the VL of node m, so node m upper bound of all frame numbers of overstocking for:

4, the comprehensive formula of above 1,2,3, can obtain calculating the overstocked computational methods of AFDX network exchange machine data:

Be understandable that, for those of ordinary skills, can be equal to according to technical scheme of the present invention and inventive concept thereof and replace or change, and all these change or replace the protection range that all should belong to the claim appended by the present invention.

Claims

1. calculate the method that in AFDX network, data overstock, comprise following steps:

Step one, AFDX network is divided into different subnets according to priority, independently carries out network analysis for each subnet, for each subnet, calculate arrival curve and the service curves of each virtual link according to the method for network checking computations;

Step 2 and then to calculate each virtual link inner due to the data delay D caused that queues up at each switch _i;

Step 3, according to data delay D _ithe data calculating each node overstock: