AFDX Overview

ARINC-664 Standard adopts the key elements from AFDX standardize a deterministic Network for aircraft

• AFDX is used on the Airbus A380 as main avionics databus & on the A400M
• AFDX is based on IEEE 802.3 standard (commercial Ethernet using wire) with either 10Mbits/s or 100Mbits/s
• AFDX uses a special protocol to provide deterministic timing and redundancy management
• The main elements of an AFDX network are:
• AFDX End Systems
• AFDX Switches
• AFDX Links

AFDX Network Topology Overview

• AFDX is rather a network than a bus
• There are two types of devices on the bus Switches and End Systems
• All connections are full-duplex 10Mbits/s or 100MBit/s (no dedicated backbone bus for Inter-Switch communication)
• Redundancy is achieved by duplication of the connections (wires) and the Switches
• AFDX uses special extensions to provide deterministic timing and redundancy
• End Systems (E/S) exchange Frames through Virtual Links (VL)
• A VL defines the unidirectional connection from one source E/S to one or more destination E/s(s)
• An E/S performs Traffic policing, Integrity Checking and Redundancy Management on a per VL basis

AFDX Traffic Policing

• The E/S controls the flow for each VL in accordance with the Bandwidth Allocation Gap (BAG)
• BAG values are in ms: 1,2 4,8, 16, 32, 64, 128

AFDX Redundancy

• The ports, links and switches are duplicated for redundancy
• Frames are transmitted concurrently on both networks

Integrity Checking is done per VL and per Network

• Invalid Frames are discarded
• Sequence Number Check

Redundancy Management

• On receiving E/S the 'First valid Frames wins'

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