Comparison of IEEE AVB and AFDX

Avionics Full Duplex Ethernet (AFDX) is a well-established backbone network with wide usage in all current aircrafts, with its first usage onboard the Airbus A380. It was initially defined by Airbus and internationally standardized by ARINC (664 Part 7). The key features are 802.3 Ethernet compatibility, static routing based on a virtual link concept, reserved bandwidth with granted bandwidth allocation gaps, transparent redundancy and — most importantly — deterministic latency and jitter bounds. Beside several proprietary real time Ethernet solutions, an emerging open standard with support of major semiconductor companies, currently introduces guaranteed timing behavior with the focus on transportation of video and audio streams. Audio Video Bridging (AVB) is a set of IEEE standards (802.1AS, 802.1Qat, 802.1Qav, 802.1BA, 1722) developed under the Audio/Video Bridging Task group as part of 802.1, which defines protocol layers above the Ethernet MAC & LLC layers. AVB addresses low latency and highly synchronized playback of audio and video with low packet loss, low jitter and low latency. By using priority queuing (PQ) and credit-based shaper algorithms (CBQ), it aims at guaranteeing a maximum latency of 2 ms over 7 hops for the highest priority class, with the transmission of several time sensitive and best effort streams in parallel. This work introduces the basic principles of the new AVB standard in details, compares it with the properties of the AFDX standard, and determines if the latency determinism of AVB is suitable for Avionic´s requirements and if the new mass market controllers and switches developed for AVB could be a cost-effective alternative for Commercial off-the-shelf (COTS) based low DAL (Design assurance Level) systems.