Why afdx is deterministic

Optimal scheduling policy for jitter control in AFDX End-System Abstract: The Avionics Full Duplex Switched Ethernet AFDX is an avionics networking protocol defined for guaranteed deterministic properties such as bounded end-to-end delay, reliability and real time data delivery to ensure required quality of service for time critical applications. The proposed scheduling policy handles a set of virtual links of the different Bandwidth Allocation Gap BAG and different frame length L max size.

The mathematical analysis of proposed scheduling policy shows that prioritizing the virtual links with the Smallest Frame Earliest results in the minimum average jitter per Virtual Link for an End System. Furthermore, the concentration of functions within the IMA Cabinet demanded increased bandwidth for communications with avionics implemented outside the Cabinet.

AFDX takes existing Ethernet physical layer technology and, using switched Ethernet in full-duplex mode as a basis, adds deterministic packet delivery, and high-integrity and high-availability mechanisms.

One mode of operation, customarily called half-duplex, gave IEEE In this mode, each end system monitors its receive port for indications that something is being transmitted. Prior to transmitting, such indications are used to avoid interfering with the ongoing transmission i. During a transmission, any indication of another transmission indicates a collision, which results in corrupted communication i.

This was the original principle of arbitrating communication, adapted from voice radio communication procedures. Figure 1 illustrates this basic comparison. The use of Ethernet permits the reuse of commercial off-the-shelf protocols, e. IP addressing and fragmentation, any Ethernet interface hardware and the switched Ethernet configuration.

But AFDX tailors these to the requirements of the avionics environment. For instance, Virtual Links, bandwidth allocation and redundant LANs add the necessary integrity, availability and deterministic performance needed for avionics applications.

We will touch on each of these refinements to the underlying Ethernet. The Aircraft Data Network defined in ARINC has been developed in several parts and written with the view that commercially available information technology standards can be applied to aviation with minimal changes.

Further, where there are selections among the commercial standards or deviations for aviation requirements, there is provision to record and disclose those selections and deviations in the form of Protocol Implementation Conformance Statements PICS and Services Implementation Conformance Statements SICS.

In Figure 3, a single Virtual Link is illustrated. A Virtual Link is defined as one source i. Each end-system transmitter and receiver is assigned a unicast MAC address.

Each VL is assigned a maximum frame size and a minimum time between two transmissions of a frame, called the bandwidth allocation gap BAG. Citation Type. Has PDF. Publication Type. More Filters. A tight end-to-end delay bound and scheduling optimization of an avionics AFDX network. Inspired by the response time analysis RTA technique, this paper presents a new method for the estimation of end-to-end delay bounds in AFDX networks. For the purpose of comparison, an end-to-end … Expand.

View 3 excerpts, cites methods and background. Ethernet-based avionic databus and time-space partition switch design. Data work mode change in AFDX network. When network mode changes, the transition time analysis of the network is especially important, as there should be no buffer overload and all switches schedulable.

To ensure the schedulability of … Expand. Methods for bounding end-to-end delays on an AFDX network.