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Figure 2: Physical topology of AFDX.............................................................. 12
Figure 3: Logical topology of AFDX................................................................ 13
Figure 4: VL scheduling with jitter................................................................... 15
Figure 5: Sub-VL Concept .............................................................................. 16
Figure 6: AFDX protocol stack........................................................................ 19
Figure 7: AFDX frame structure...................................................................... 21
Figure 8: AFDX Integrity Checking and Redundancy Management .............. 23
Figure 9: AFDX Switch Architecture ............................................................... 25
List of Tables
Table 1: AFDX protocol overhead including leading and trailing bytes.......... 29
List of Formulas
Formula 1: Bandwidth constraints of messages on the same VL .................. 27
Formula 2: Example using Formula 1 for two messages on the same VL..... 28
Formula 3: AFDX message network load....................................................... 29
Formula 4: Bandwidth constraints from a message point of view .................. 30
Formula 5: Bandwidth constraints from a VL point of view ............................ 30
6/30 700008_TUT-AFDX-EN_1000
List of Abbreviations
Abbreviation Text
ADN Aircraft Data Network
AFDX Avionics Full Duplex Switched Ethernet
ARINC Aeronautical Radio Incorporated
BAG Bandwidth Allocation Gap. BAG is a property of a VL and is given in ms
BER Bit Error Ratio - The number of erroneous bits to the total bit number of bits
COTS Commercial Of The Shelf
CRC Cyclical Redundancy Checking. A data integrity detection method
ES End System - LRU or part of an LRU implementing the network communication
interface
FCS Frame Check Sequence
FIFO First In First Out
IEEE802.3 Ethernet protocol standard from "Institute of Electrical & Electronics Engineers"
IFG Inter Frame Gap
IP Internet Protocol
Jitter Network transmit latency caused by data contention
Latency Network transmit latency caused by software and hardware layers in the ES
LRU Line Replaceable Unit
MAC Media Access Controller
MTC Message Transmit Cycle. MTC is a property of a message and is given in ms
MTU Maximum Transfer Unit. MTU is a property of a VL and is given in bytes
PL Message payload data. PL is a property of a message and is given in bytes
QoS Quality of Service
RFC Request for Communication. Standard for protocols on top of IEEE802.3
RSN Redundancy Sequence Number
SAP Service Access Point
SFD Start Frame Delimiter
TCP Transmission Control Protocol
TFTP Trivial File Transfer Protocol
UDP User Datagram Protocol
VL Virtual Link. A virtual or logical communication channel
AFDX® / ARINC 664 Tutorial 7/30
Scope
The purpose of this tutorial is to give a description of the Avionics Full Duplex
Switched Ethernet (AFDX®) which is a communication standard for an Aircraft Data
Network (ADN). The description will provide the reader with an overview of the
fundamentals of the AFDX network architecture, network protocol, network
communication concept and network reliability.
The tutorial is based on the standard ARINC 664 which is an AFDX standard defined
by Aeronautical Radio, Incorporated (ARINC) and Airbus. Meanwhile Boeing has
defined a special version of AFDX which is based on the ARINC 664 standard and is
backwards compatible with this. However, the specialties of the Boeing standard are
not described herein.
It is assumed that the reader, as a minimum, is familiar with the principles of data
communication. In particular, knowledge of the Ethernet communication standard is a
definite advantage to understand the contents of this tutorial.
AFDX® / ARINC 664 Tutorial 9/30
Overview
Aircraft Data Network (ADN) Characteristics
The most important characteristics of an ADN are Quality of Service (QoS), available
bandwidth, weight and the cost of its development and deployment.
Various ADN attributes such as bandwidth guarantee, jitter, transmit latency and Bit
Error Ratio (BER) determine the QoS. A guaranteed bandwidth, limited jitter, upper
bounded transmit latency and a low BER (typically 10-12, i.e. one error bit in a
trillion) are imperative attributes of a reliable and deterministic ADN.
New generation aircraft such as the A380, A350, B787 and A400M are required to
feature more sophisticated functions than previous aircraft generations. For reasons of
weight savings, less required space as well as reduced maintenance costs it is desired
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