Application of Network Calculus To Guaranteed Service Networks

We use recent network calculus results to study some properties of lossless multiplexing as it may be used in guaranteed service networks. We call network calculus a set of results that apply min-plus algebra to packet networks. We provide a simple proof that shaping a traffic stream to conform with a burstiness constraint preserves the original constraints satisfied by the traffic stream We show how all rate based packet schedulers can be modeled with a simple rate latency service curve. Then we define a general form of deterministic effective bandwidth and equivalent capacity. We find that call acceptance regions based on deterministic criteria (loss or delay) are convex, in contrast to statistical cases where it the complement of the region which is convex. We thus find that, in general, the limit of the call acceptance region based on statistical multiplexing when the loss probability target tends to 0 may be strictly larger than the call acceptance region based on lossless multiplexing. Lastly, we consider the problem of determining the optimal parameters of a variable bit rate (VBR) connection when it is used as a trunk, or tunnel, given that the input traffic is known. We find that there is an optimal peak rate for the VBR trunk, essentially insensitive to the optimization criteria. For a linear cost function, we find an explicit algorithm for the optimal remaining parameters of the VBR trunk

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

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)

Network on Chip: a New Approach of QoS Metric Modeling Based on Calculus Theory

A NoC is composed by IP cores (Intellectual Propriety) and switches connected among themselves by communication channels. End-to-End Delay (EED) communication is accomplished by the exchange of data among IP cores. Often, the structure of particular messages is not adequate for the communication purposes. This leads to the concept of packet switching. In the context of NoCs, packets are composed by header, payload, and trailer. Packets are divided into small pieces called Flits. It appears of importance, to meet the required performance in NoC hardware resources. It should be specified in an earlier step of the system design. The main attention should be given to the choice of some network parameters such as the physical buffer size in the node. The EED and packet loss are some of the critical QoS metrics. Some real-time and multimedia applications bound up these parameters and require specific hardware resources and particular management approaches in the NoC switch. A traffic contract (SLA, Service Level Agreement) specifies the ability of a network or protocol to give guaranteed performance, throughput or latency bounds based on mutually agreed measures, usually by prioritizing traffic. A defined Quality of Service (QoS) may be required for some types of network real time traffic or multimedia applications. The main goal of this paper is, using the Network on Chip modeling architecture, to define a QoS metric. We focus on the network delay bound and packet losses. This approach is based on the Network Calculus theory, a mathematical model to represent the data flows behavior between IPs interconnected over NoC. We propose an approach of QoS-metric based on QoS-parameter prioritization factors for multi applications-service using calculus model

Performance analysis of a Master/Slave switched Ethernet for military embedded applications

Current military communication network is a generation old and is no longer effective in meeting the emerging requirements imposed by the next generation military embedded applications. A new communication network based upon Full Duplex Switched Ethernet is proposed in this paper to overcome these limitations. To allow existing military subsystems to be easily supported by a Switched Ethernet network, our proposal consists in keeping their current centralized communication scheme by using an optimized master/slave transmission control on Switched Ethernet thanks to the Flexible Time Triggered (FTT) paradigm. Our main objective is to assess the performance of such a proposal and estimate the quality of service we can expect in terms of latency. Using the Network Calculus formalism, schedulability analysis are determined. These analysis are illustrated in the case of a realistic military embedded application extracted from a real military aircraft network, to highlight the proposal's ability to support the required time constrained communications

Improved Delay Bound for a Service Curve Element with Known Transmission Rate

Network calculus is often used to prove delay bounds in deterministic networks, using arrival and service curves. We consider a FIFO system that offers a rate-latency service curve and where packet transmission occurs at line rate without pre-emption. The existing network calculus delay bounds take advantage of the service curve guarantee but not of the fact that transmission occurs at full line rate. In this letter, we provide a novel, improved delay bound which takes advantage of these two features. Contrary to existing bounds, ours is per-packet and depends on the packet length. We prove that it is tight.Comment: 4 pages, 2 figure