Overview of AFDX
AFDX adopted concepts (token bucket) from the telecom standard, Asynchronous Transfer Mode (ATM), to fix the shortcomings of IEEE 802.3 Ethernet. By adding key elements from Asynchronous Transfer Mode (ATM) to those already found in Ethernet, and constraining the specification of various options, a highly reliable Full-Duplex deterministic network is created providing guaranteed bandwidth and Quality of Service. Through the use of Full-Duplex Ethernet, the possibility of transmission collisions is eliminated. However, though bandwidth and maximum end-to-end latency and jitter, links are guaranteed, there is no guarantee of packet delivery. A highly intelligent switch, common to the AFDX network, is able to buffer transmission and reception packets. Through the use of twisted pair or fiber optic cables, Full-Duplex Ethernet uses two separate pairs or strands for transmit and receiving data. AFDX extends standard Ethernet to provide high data integrity and deterministic timing. Further a redundant pair of networks is used to improve the system integrity (although a VL may be configured to use one or other network only) It specifies interoperable functional elements at the following OSI Reference Model layers:
- Data Link (MAC and Virtual Link addressing concept);
- Network (IP and ICMP);
- Transport (UDP and optionally TCP)
- Application (Network) (Sampling, Queuing, SAP, TFTP and SNMP).
The main elements of an AFDX network are:
- AFDX End Systems
- AFDX Switches
- AFDX Links
Read more about this topic: Avionics Full-Duplex Switched Ethernet