Calculus of service guarantees for network coding

A large class of networks is able to provide some guarantees in terms of quality of service, end-to-end delays and throughput to data flows. In return, the data flows must verify constraints of burstiness and throughput. The aim of this work is to introduce and evaluate the network coding for independent flows in such networks. First, we present efficient coding nodes strategies allowing the building of output flows as a combination of a subset of all the input flows. These strategies are evaluated in terms of maximal output throughput, maximum buffer size and maximal crossing-delays of the network node. In a second part, we show that a generalization of these results to a complete network can be obtained through a transfer matrix whose entries are expressed in terms of network calculus. Thanks to the formalism used to characterize the flows, the obtained results can be considered as guarantees in terms of the burstiness, buffers size or end-to-end delays

A Deterministic Polynomial--Time Algorithm for Constructing a Multicast Coding Scheme for Linear Deterministic Relay Networks

We propose a new way to construct a multicast coding scheme for linear deterministic relay networks. Our construction can be regarded as a generalization of the well-known multicast network coding scheme of Jaggi et al. to linear deterministic relay networks and is based on the notion of flow for a unicast session that was introduced by the authors in earlier work. We present randomized and deterministic polynomial--time versions of our algorithm and show that for a network with $g$ destinations, our deterministic algorithm can achieve the capacity in $\left\lceil \log(g+1)\right\rceil$ uses of the network.Comment: 12 pages, 2 figures, submitted to CISS 201

Guaranteed packet delays with network coding

In the context of networks providing QoS guarantees, the end-to-end delay experienced by a packet is an important parameter. In this paper, we show that network coding can be used to decrease worst case end-to-end bounds when compared to a classical routing strategy. This result can be explained by the fact that network coding can cope with congestion better that classical routing due to its property to process simultaneously packets from different flows. In this paper, two network coding strategies, applied to networks providing QoS guarantees, are presented. We present an evaluation of worst case delays both in routing and coding approaches with network calculus tools. An interesting result is that network coding can improve these guaranteed end-to-end bounds even in network topologies where the throughput is not improved

Using network calculus to optimize the AFDX network

This paper presents quantitative results we obtained when optimizing the setting of priorities of the AFDX traffic flows, with the objective to obtain tighter latency and queue-size deterministic bounds (those bounds are calculated by our Network Calculus tool). We first point out the fact that setting randomly the priorities gives worse bounds than using no priorities, and we then show experiments on the basis of classic optimization techniques such as a descent method and a tentative AlphaBetaassisted brute-force approach: both of them haven’t brought significantly better results. We finally present experiments based on genetic algorithms, and we show how driving these algorithms in an adequate way has allowed us to deliver a full range of priority configurations that bring tighter bounds and allow the network traffic designer to trade off average gains of 40% on all the latency bounds against focused improvement on the largest queue-size bound (up to a 30% reduction)

Differentiable Programming & Network Calculus: Configuration Synthesis under Delay Constraints

With the advent of standards for deterministic network behavior, synthesizing network designs under delay constraints becomes the natural next task to tackle. Network Calculus (NC) has become a key method for validating industrial networks, as it computes formally verified end-to-end delay bounds. However, analyses from the NC framework have been designed to bound the delay of one flow at a time. Attempts to use classical analyses to derive a network configuration have shown that this approach is poorly suited to practical use cases. Consider finding a delay-optimal routing configuration: one model had to be created for each routing alternative, then each flow delay had to be bounded, and then the bounds had to be compared to the given constraints. To overcome this three-step process, we introduce Differential Network Calculus. We extend NC to allow the differentiation of delay bounds w.r.t. to a wide range of network parameters - such as flow paths or priority. This opens up NC to a class of efficient nonlinear optimization techniques that exploit the gradient of the delay bound. Our numerical evaluation on the routing and priority assignment problem shows that our novel method can synthesize flow paths and priorities in a matter of seconds, outperforming existing methods by several orders of magnitude

Theories and Models for Internet Quality of Service

We survey recent advances in theories and models for Internet Quality of Service (QoS). We start with the theory of network calculus, which lays the foundation for support of deterministic performance guarantees in networks, and illustrate its applications to integrated services, differentiated services, and streaming media playback delays. We also present mechanisms and architecture for scalable support of guaranteed services in the Internet, based on the concept of a stateless core. Methods for scalable control operations are also briefly discussed. We then turn our attention to statistical performance guarantees, and describe several new probabilistic results that can be used for a statistical dimensioning of differentiated services. Lastly, we review recent proposals and results in supporting performance guarantees in a best effort context. These include models for elastic throughput guarantees based on TCP performance modeling, techniques for some quality of service differentiation without access control, and methods that allow an application to control the performance it receives, in the absence of network support

Real-time characteristics of switched ethernet for "1553B" -embedded applications : simulation and analysis

In our previous work , Full Duplex Switched Ethernet was put forward as an attractive candidate to replace the MIL-STD 1553B data bus, in next generation "1553B"-embedded applications. An analytic study was conducted, using the Network Calculus formalism, to evaluate the deterministic guarantees offered by our proposal. Obtained results showed the effectiveness of traffic shaping techniques, combined with priority handling mechanisms on Full Duplex Switched Ethernet in order to satisfy 1553B-like real-time constraints. In this paper, we extend this work by the use of simulation. This gives the possibility to capture additional characteristics of the proposed architecture with respect to the analytical study, which was basically used to evaluate worst cases and deterministic guarantees. Hence, to assess the real-time characteristics of our proposed interconnection technology, the results yielded by simulation are discussed and average latencies distributions are considered