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Comparison between ADN (Aircraft Data
Network) and Internet world
Sui FAN Department of Electronics Engineer Beijing University of Posts and Telecommunications / Telecom ParisTECH Beijing, P. R. China 100876 Sui.fan @eurecom.fr
Abstract
Since ARINC 664/AFDX standard has been selected for wide use in principal aircraft network in advanced airplanes. New generation Aircraft Network is currently under definition to enhance the AFDX in Aircraft Data Network with higher throughput and the support of more applications to open the door between Avionics Data Network and Internet world, which will introduce certain potential security issues. Therefore, this paper is going to introduce the difference between the two worlds.
Keywords: AFDX, Internet world, OSI, Virtual Link, Security
1 Introduction
From 1980th until recently, as the development of technique, ARINC 429,629,664 has been applied in different airplanes with different features. Especially now AFDX is popularly applied in advanced airplanes as local aircraft network communication protocol in Europe. Compared with Eureope, we are making progress recently but it’s still far than enough from catching up. The work is to study Avionics standards, including the basic AFDX tutorials and proposed security analysis draft by some AEEC working groups.
Authors’ names are set in boldface, and each name is centered above the corresponding address. The lead author’s name is to be listed first (left-most), and the co-authors’ names (if different address) are set to follow. If only one co-author, list both author and co-author side by side.
Please pay special attention to the instructions in section 3 regarding figures, tables, acknowledgements, and references.
2 History of Avionics network standards
Currently, the network architectures onboard avionics are important developments due mainly to incr
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eased complexity of embedded systems, in terms of growth of functions and therefore connections between these functions. These complexity problems have to be faced by taking advantage of technological developments based on the concept of architecture modular (which targets a greater share of resources for treatment and communication). Multi communications is one of the major challenges of new architectures generation. Various proposals about bus in avionics communication have been made, in particular under the ARINC which is the body architectures of civilian aircraft standards. Prior to AFDX, Aircraft Data Networks (ADN) utilized primarily the ARINC 429 standard. This standard, developed over thirty years ago and still widely used today, has proven to be highly reliable in safety critical applications. This ADN can be found on a variety of aircraft from both Boeing and
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Airbus, including the Boeing 737, 747, 757, 767 and Airbus A330 and A340. ARINC 429 utilizes a unidirectional bus with a single transmitter and up to twenty receivers. A data word consists of 32 bits communicated over a twisted pair cable using the Bipolar Return-to-Zero Modulation. There are two
speeds of transmission: high speed operates at 100 kbit/s and low speed operates at 12.5 kbit/s. ARINC 429 operates in such a way that its single transmitter communicates in a point-to-point connection, thus requiring a significant amount of wiring which amounts to added weight. Table 2-1:List of the avionics network history
TIME STANDARDs SPEED
SUPPORT FEATURE APPLIED
AIRPLANES
1988 ARINC 429 12.5 ~ 100 kbit/s Unidirectional data bus standard; Single-transmitter multi-drop bus with up to 20 receivers B727,B737, B747,B757, B767, A310/A320, A330/A340
1999 ARINC 629 2 Mbit/s
8 Mbit/s Multi-transmitter protocol
B777 2005 ARINC 664,
AFDX
100Mbits/s Based on ATM, Ethernet 802.3;
Single-transmitter with receivers limited only by the number of ports on the switch A380, A400M, A350B787, 2008~ 2010 New Generataion study 1Gbit/s+
On the study and research Advanced avion However, most of these proposals are based on media Communications which are old enough, as the ARINC 429 are reliable but with limited performance (100 kbit / s) who do not satisfy the requests from airline manufacturers today, even if they are of simplicity and reliability important.
Another standard, ARINC 629, introduced by Boeing for the 777 provides increased data speeds of up to 2 Mbit/s and allowing a maximum of 120 data terminals. This improvement in avionics bus takes into account the constraints of determinism and real-time specific avionics applications directly at the level of techniques Time multiplexing proposed. This ADN operates without the use of a bus controller thereby increasing the reliability of the network architecture. The draw back of this system is that it requires hardware which can add significant cost to the aircraft. Because of this, other manufactures did not openly accept the ARINC 629 standard.
The changing technology of local transmission of data (Ethernet switched, ATM, ...) has provided ne
w answers to aircraft manufacturers and consider their use even if the nature of non-deterministic Users must be offset by strong assumptions, including trafficking the network. The solution adopted by Airbus for the new generation A380 is to reuse the basics of switched Ethernet. This technology allows a reuse of development tools and hardware components, which is to have a good confidence equipment reliability and ease of maintenance.
ARINC 664 is defined as the next-generation aircraft data network (ADN). It is based upon IEEE 802.3 Ethernet and utilizes commercial off-the-shelf (COTS) hardware thereby reducing costs and development time.
AFDX (Avionics Full Duplex switched Ethernet) is formally defined in Part 7 of the ARINC 664 specification. It has since been accepted by Boeing and is used on the Boeing 787 Dreamliner. AFDX bridges the gap on reliability of guaranteed bandwidth from the original ARINC 664 standard. It utilizes a star topology network of up to 24 end systems that are tied to a switch, where each switch can be bridged together to other switches on the network. By utilizing this form of network structure,
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AFDX is able to significantly reduce wire runs thus reducing overall aircraft weight. Additionally, AFDX provides dual link redundancy and Quality of Service (QoS).我的
职业选择 However, switches prescribed by the standard ARINC664 conform to the IEEE 802.1D, is possible to lose frames. The problem comes from the level of switches, where different flows will compete for the use of the switch. Indeed, the confluences of traffic are potentially sources of non-determinism of latency through the network and can cause congestion of ports output switches. To address this problem of non-determinism in the AFDX network, several methods for analyzing temporal properties of communication media (latency, throughput, jitter, ...) were used.
Besides, security exposure since it adopts the same Internet protocol nowadays while previously the security issues doesn’t exit because those old ADN standards are not compatible with the "Internet open world".
3 Illustration of AFDX
民国小学生作文3.1 A FDX Pr otoco l
The new generations of aircraft boarded more avionics systems, increasing both safety and passenger comfort. These new functions result in a sharp increase in exchanges of data, which requires more flow and opportunities interconnection. The conventional buses communications avionics cannot answer this new demand, which has pushed manufacturers (Airbus and Boeing) to install a network board communication using switched Ethernet technology, also bring the era of AFDX.
A vionics F ull D uple X Switched Ethernet (AFDX) is a standard that defines the electrical and protocol specifications (IEEE 802.3 and ARINC 664, Part 7) for the exchange of data between Avionics subsystems, to enable interconnection of system throughout the aircraft. It has three components :Avionics Subsystems, AFDX End System, AFDX Interconnect.
Figure 3-1 AFDX Components in Avionics
3.1.1 P ra ct ica l n et w o rk s t ru c tu r e
Our proposed security mechanism should work for different kinds of environment, not only in A380, but to have an intuitive idea. Let’s have a look at the network structure embedded in current real Avionics first.
Figure 3-2 Network structure embedded in Avionics
Figure 3-3 Practical AFDX Topology in A380 (Airbus)
-4-
-5- In this real network structure, we could find all the transmitters or receivers (also called End System) connected with Switches, simply and almost symmetrical, using Star Topology. For every End System connected with Switch, there are two in case of redundancy (red and blue colour).
The network consists of a hundred End System (123 End Systems), and 2x9 switches. These switches use FIFO policy.
As a network-Full Duplex, of course each End System is linked to a single switch. Traffic on the Industrial AIRBUS is made up of 984 multicast streams, with between 1 and 15 recipients. Generally, hundreds of bytes in a frame can be more efficient than small bytes or large bytes.
Note that in the structure, there are two Models called “SCI”, Security Control Interface, which are used to run some software filter function when connecting with Open World.
3.2 C omp ar is o n Be tw ee n ADN an d I nt e rn et
3.2.1 Mo de l C om p ar is on Be t w een ADN an d Int e rn e t
Difference between AFDX and worldwide Internet in the Layer model lies mainly in the Data Link
Layer.
Figure 3-4 AFDX under OSI
Figure 3-5 End System Protocol Layers
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