Space Partitioned AFDX Switch Design Based On Shared Memory Architecture

As a new generation of aviation network communication standard, AFDX has beenapplied to the A380and other large civil aircrafts due to its advantages of full-duplex,high-bandwidth, low latency, low packet loss ratio and low cost. As the major components ofan AFDX network, switches are key devices influencing the overall performance of an AFDXnetwork. Shared memory architecture is widely used but it has imperfect reliability andscalability, because all the input and output ports share only one memory and one scheduler,which will lead to severe resource contention and scheduling latency.This article employs space partition technique to isolate the memory space for each inputand output port and asynchronous scheduling technique to ease the burden of the switchscheduler, and proposes a new space partitioned shared memory switch (SPSMS) architecturefor AFDX networks with these two techniques.The main work and research results are summarized as follows:(1) Make a deep research into AFDX protocol and AFDX network, including itscomponents, characteristics and properties which are different from other types of networks’.Avionics Subsystems, AFDX End Systems (ES), AFDX Interconnect and Virtual Links (VL)are four quite significant parts of an AFDX network. And one of outstanding characteristicsan AFDX network owns is the stability of network capacity, bandwidth and routing tables ofAFDX switches. It is realized that AFDX switches play a quite important role in an AFDXnetwork.(2) A broad and deep survey of various types of switches is conducted, and then the shared memory architecture is emphasized due to its simple, low hardware cost and highhardware utilization ratio. The advantages and disadvantages of shared memory architectureare summarized. And it’s pointed out that whether a property of shared memory architectureis suitable for AFDX networks.(3) Combined with the stability nature of AFDX networks and the plainness andefficiency of shard memory architecture, a new space partitioned shared memory switchdesign is proposed, namely SPSMS switch. First, SPSMS switch reduces the competition formemory resources and avoid conflicts, thereby decreasing the latency of packets through theswitch. Furthermore, packet overflow is reduced to a great extent so long as the size of thememory corresponding to some output port is larger than the product of its highest flow rateand scheduling unit, which can be achieved since the avionic network flows are predictable.Due to this, the packet loss ratio is also greatly decreased.(4) Simulation of SPSMS and plain shared memory switch with OPNET Modeler showssignificant performance improvement over a classical shared memory switch in terms ofoverall switch packet latency, queuing delay and queue size.