Network Calculus

Architectures of avionics networks, such as that of the Airbus A380, currently know important evolutions. This is principally due to the increase in the complexity of the embedded systems, in term of rise in number of integrated functions and their connectivity. The evolution of switched Ethernet technologies allows their implementation as an avionics architecture (AFDX: avionics full duplex switched Ethernet). The problem is then to prove that no frame is lost by the network (no switch queue will overflow) and to evaluate the end-to-end transfer delay through the network. The objective of this paper is to present and shortly compare three methods for the evaluation of end-to-end delays: network calculus, queuing networks simulation and model checking

The establishment of the overall ob- jectives of a distributed sensor network is a dynamic task so that it may sufficiently well 'track' its environ- ment. Both resource allocation to each input data flow and congestion control at each decision node of such a network must be performed in an integrated frame- work such that they are sensitive to this

The IEEE 802.15.4 protocol has the ability to support time-sensitive wireless sensor network (WSN) applications due to the guaranteed time slot (GTS) medium access control mechanism. Recently, several analytical and simulation models of the IEEE 802.15.4 protocol have been proposed. Nevertheless, currently available simulation models for this protocol are both inaccurate and incomplete, and in particular they do not support the GTS mechanism. In this paper, we propose an accurate OPNET simulation model, with focus on the implementation of the GTS mechanism. The motivation that has driven this work is the validation of the network calculus based analytical model of the GTS mechanism that has been previously proposed and to compare the performance evaluation of the protocol as given by the two alternative approaches. Therefore, in this paper we contribute an accurate OPNET model for the IEEE 802.15.4 protocol. Additionally, and probably more importantly, based on the simulation model we propose a novel methodology to tune the protocol parameters such that a better performance of the protocol can be guaranteed, both concerning maximizing the throughput of the allocated GTS as well as concerning minimizing frame delay.

Packet Scale Rate Guarantee (PSRG) is a generic node model which underlies the definition of Expedited Forwarding (EF) proposed in the context of Internet Differentiated Services. For the case of FIFO nodes, PSRG is equivalent to the well-understood concept of adaptive service curve. However, in practice, many devices do not necessarily preserve the FIFO property, and therefore known FIFO results do not hold. This paper analyzes the properties of PSRG in the absence of FIFO assumption. Our analysis is based on a novel characterization of PSRG which avoids the use of virtual finish times; it is obtained by min-max algebra. We use it to show that delay bounds previously obtained for the FIFO case are still valid; in contrast, we find that this is not true for the characterization of the concatenation of two nodes.

Network calculus is a theory dealing with queueing type problems encountered in computer networks, with particu- lar focus on quality of service guarantee analysis. Queueing theory is the mathematical study of queues, proven to be applicable to a wide area of problems, generally concerning about the (average) quantities in an equilibrium state. Since both network calculus and queueing theory are analytical tools for studying queues, a question arises naturally as is if and where network calculus and queueing theory meet. In this paper, we explore queueing principles that underlie net- work calculus and exemplify their use. Particularly, based on the network calculus queueing principles, we show that for GI/GI/1, similar inequalities in the theory of queues can be derived. In addition, we prove that the end-to-end per- formance of a tandem network is independent of the order of servers in the network even under some general settings. Through these, we present a network calculus persp...

The stochastic network calculus (SNC) is a recent method-
ology to analyze queueing systems in terms of probabilis-
tic performance bounds. It complements traditional queue-
ing theory and features support for a large set of trac
arrivals as well as dierent scheduling algorithms. So far,
there had been no tool support for SNC analyses. There-
fore, we present the DISCO Stochastic Network Calcula-
tor (DISCO-SNC) version 1.0, a Java library supporting the
modelling and analysis of feedforward queueing networks us-
ing the SNC. The DISCO-SNC allows to calculate proba-
bilistic delay and backlog bounds given a feedforward topol-
ogy consisting of work-conserving servers and a set of ows
traversing the network. While the DISCO-SNC is still in
its infancy it is designed in a modular fashion to allow for
an easy extension of, e.g., trac types and scheduling al-
gorithms; furthermore, it performs the optimization of free
parameters as they usually appear during SNC analyses due
to the application of the Cherno bound or H

older inequal-
ity. Apart from this core functionality, the DISCO-SNC also
provides a exible GUI to make the SNC accessible even for
SNC-unexperienced users.

Abstract In this paper we investigate link scheduling for Wireless Mesh Networks (WMNs) carrying real-time (ie, delay-constrained) traffic. We show that the problem of computing a conflict-free link schedule with end-to-end delay constraints can be formulated as a mixed-...

The IEEE 802.15.4 protocol has the ability to support time-sensitive wireless sensor network (WSN) applications due to the guaranteed time slot (GTS) medium access control mechanism. Recently, several analytical and simulation models of the IEEE 802.15.4 protocol have been proposed. Nevertheless, currently available simulation models for this protocol are both inaccurate and incomplete, and in particular they do not support the GTS mechanism. In this paper, we propose an accurate OPNET simulation model, with focus on the implementation of the GTS mechanism. The motivation that has driven this work is the validation of the network calculus based analytical model of the GTS mechanism that has been previously proposed and to compare the performance evaluation of the protocol as given by the two alternative approaches. Therefore, in this paper we contribute an accurate OPNET model for the IEEE 802.15.4 protocol. Additionally, and probably more importantly, based on the simulation model we propose a novel methodology to tune the protocol parameters such that a better performance of the protocol can be guaranteed, both concerning maximizing the throughput of the allocated GTS as well as concerning minimizing frame delay.

Having in mind that real-time streams tolerate some deadline misses according to (m,k)-firm constraints [1], this paper presents a solution that consists in integrating (m,k)-firm temporal requirements into the guaranteed-rate quality of service such as IntServ Model to provide both bandwidth and delay guarantees as required by real-time applications. Analytic study using Network Calculus gives the upper bound on delay guaranteed by the proposed approach and shows better behavior compared to the classical IntServ QoS model.