Guaranteed real-time communication in packet-switched networks with FCFS queuing

Abstract

In this paper, we propose a feasibility analysis of periodic hard real-time traffic in packet-switched networks using First Come First Served (FCFS) queuing but no traffic shapers. Our work constitutes a framework that can be adopted for realtime analysis of switched low-cost networks like Ethernet without modification of the standard network components. Our analysis is based on a flexible network and traffic model, e.g., variable-sized frames, arbitrary deadlines and multiple switches. The correctness of our real-time analysis and the tightness of it for network components in single-switch networks are given by theoretical proofs. The performance of the end-to-end real-time analysis is evaluated by simulations. Moreover, our conceptual and experimental comparison studies between our analysis and the commonly used Network Calculus (NC) shows that our analysis can achieve better performance than NC in many cases.

Analytic Calculus of Response Time in Networked Automation Systems

“…This answer crosses the network and gets to NETb (3). At the beginning of a new CPU cycle, this answer is used to execute the user program (4) to perform the reaction event (5) that will be sent to its destination at the next scanning cycle (6). Again, this answer crosses the network to get to RIOM (7) and finally to the plant (8) (destination D).…”

“…With such a protocol therefore, resource scheduling is unavailable and considerable delays due to unsynchronized or unavailable resources are caused, complicating the evaluation of message delay encountered in each system component and consequently impeding an evaluation of the entire system response time. A number of research efforts have been undertaken to assess these NAS delays through the use, for example, of widely-accepted network calculus [3], [4], [5], worst case methods [6], [7] and simulation [8], [9]. Like the majority of studies however, these efforts have focused on just the end-to-end delays or network effect and neglect both the controllers (e.g.…”

Predictable real-time communications with improved reliability for IEEE 802.15.4 based industrial networks

“…In [8], hard real-time guaran tees are provided for traffic flows including retransmis sions, but the approach relies on the existence of traffic regulators in each node. In addition, the analysis lacks timing details and uses flow analysis which in [9] was shown to give lower network utilization than the real time analysis used in our framework.…”

Towards Reliable Wireless Industrial Communication With Real-Time Guarantees

“…Therefore, we set (17) In order to derive the delay bound for ordinary transmissions, (1) is rephrased as (18) As for the ordinary transmission, the new deadline of each retransmission, i.e., the isolated maximum queueing delay can be calculated by subtracting all other delays from the delay bound (further elaborated on at a later point in this paper) (19) where (20) The last possible retransmission has no ACK answer which results in fewer delay components. In (20), is included as the maximum blocking time introduced by a packet with a longer deadline (thereby actually having a lower priority), as its nonpreemptive transmission already might have been initiated.…”

“…However, their methods use flow analysis, which has been shown to not fully exploit the available network capacity compared to real-time scheduling analysis [18]. Additionally, their analysis does not include the timing details needed to support hard real-time communication in embedded and industrial real-time systems, while the here presented solution is targeting an as exact analysis as possible.…”