An approach to comply with real-time traffic constraints over a multi-hop factory network

In this paper we address the transmission of real-time flows over a point-to-point, multi-hop factory intranet in congestion conditions, and propose innovative approaches to address timeliness requirements of real-time flows in a per-flow way. Our aim is to integrate the current IP with a specific service for real-time traffic in order to meet the constraints of real-time traffic even in periods of congestion. To achieve this, we assume that the routers will provide diversified scheduling for real-time and nonreal-time flows, keeping the two types of traffic in separate queues and applying a deadline-based scheduling to real-time flows and a FIFO policy to nonreal-time traffic. Moreover, we assign each packet belonging to a real-time flow an "end-to-end deadline", which has to be split into n "hop-deadlines", referring to the hops the packet has to make from the source host to the destination one. In the paper, different strategies which differ in the way packets are scheduled inside the routers and also in the hop-deadline calculations, are presented and evaluated.