Abstract

In this paper, to improve the burst loss performance, we actively avoid contentions by proposing a novel congestion control scheme that operates based on the highest (called peak load) of the loads of all links over the path between each pair of ingress and egress nodes in an Optical Burst Switching (OBS) network. Document type: Part of book or chapter of book

Abstract

This paper addresses the issue of pricing-based distributed resource allocation via scheduling in a communication network. Introducing the temporal aspect in the resource allocation problem presents new challenges e.g. in accounting for the durations and deadlines of the resource requests. Dynamic real-time pricing concepts are discussed for the decentralized sharing of network resources. A numerical example illustrates the benefit of congestion based pricing in a dynamic communication network. The quality of service that results from decentralized resource allocation is studied from the point of view of a power-controlled wireless network. The model is based on a dynamic noncooperative game and is related to recent work on centrally optimal (Pareto-optimal) distributed dynamic resource allocation. Document type: Part of book or chapter of book

Abstract

International audience; This paper presents our approach integrating a high level of intelligence within telecommunication networks. Artificial intelligence has proved its efficiency in resolving complex issues in different fields like air traffic control, robotics, and medical diagnosis. However its usage in telecommunication networks is still very moderated. The main objectives of our framework is to encourage the deployment of techniques characterized by a high level of intelligence – inspired from the artificial intelligence domain in networking. For this reason, we build an extension, with intelligent capabilities, to the J-Sim simulation environment. This extension proposes an intelligent package having the essential entities required for simulating intelligent features. Using this intelligent package and the abstract node model (INET) proposed by J-Sim for network simulations, it will be possible to test the efficiency of integrating intelligent techniques in networking. Document type: Part of book or chapter of book

Abstract

This paper presents a prototype for single-rate reliable multicast congestion control, which has been built into an existing commercial whiteboard. The prototype was developed using a novel scheme that was engineered around conflicting industry provided requirements for collaborative workspaces. This required the scheme to be both low-weight when used with many senders and compatible with NAT, firewalls and reflectors. The key to overcome this conflict was to combine congestion control and recovery feedback. This differs from many current solutions in that they are often designed for use with a wide variety of protocols and thus operate independent of the recovery mechanism. This paper does not go into the detail required to specify a protocol but instead discusses a few important design requirements for multi-sender applications, which are generally not considered by current research, and describes an approach towards meeting these requirements. Document type: Part of book or chapter of book

Abstract

Aspects of a draft version of the Aeronautical Telecommunications Network (ATN) Standards and Recommended Practices (SARPs) under development by ISO-compliant committees of the International Civil Aviation Organization (ICAO) have been mathematically modelled using a formal description technique. The ATN SARPs are a specification for a global telecommunications network for air traffic control systems. A version of Harel’s statecharts formalism embedded within a machine readable typed predicate logic has been used as a formal description technique to construct this mathematical model. Our model has been `typechecked’ to partially validate the internal consistency of the specification. The work described in this paper has already uncovered some problems in the draft SARPs, and will provide a basis for follow-on efforts to apply formal analysis methods such as model-checking and symbolic execution to aspects of the ATN SARPs. The success of this approach suggests that typed predicate logic is useful as a syntactic and semantic foundation for specialized Formal Description Techniques (FDTs). Document type: Part of book or chapter of book

Abstract

The TCP protocol exhibits poor performance in multi-hop Mobile Ad Hoc Networks (MANETs). The ultimate reason for this is that MANETs behave in a significantly different way from traditional wired networks (like the Internet) for which the TCP protocol was originally designed. In particular, route failures and route changes due to node mobility may be frequent events in MANETs. Furthermore, congestion phenomena in MANETs are essentially different from traditional wired networks. In this paper we propose a novel transport protocol for MANETs. Unlike other proposals, our protocol is not a modification of the TCP but is specifically tailored to the characteristics of the MANET environment. It is able to manage efficiently route changes and route failures. Furthermore, it includes a completely re-designed congestion control mechanism. Finally, it is designed in such a way to reduce as much as possible the number of useless retransmissions. This is extremely important since retransmissions consume energy. Document type: Part of book or chapter of book

Abstract

In this paper, we present an analysis on optimization and risk management in Communication Networks (CNs). The model is proposed for offline traffic engineering optimization, which takes a centralized view of bandwidth allocation, performance control, and risk control of network profit shortfall. First, we introduce a linear penalty cost in the CN optimization model and derive the optimal bandwidth capacity with the penalty cost. Then, we use the mean-variance approach to analyze the profit shortfall risk in CNs. Finally, numerical results are shown to reveal the impact of the penalty cost on the CNs performance. Document type: Part of book or chapter of book

Abstract

In this paper, the concept of fairness in computer networks is investigated. We motivate the need of examining fairness issues by providing example future application scenarios where fairness support is needed in order to experience sufficient service quality. Fairness definitions from political science and their application to computer networks are described and a state-of-the-art overview of research activities in fairness, from issues such a queue management and tcp-friendliness to issues like fairness in layered multi-rate multicast scenarios, is given. We contribute with this paper to the ongoing research activities by defining the fairness challenge with the purpose of helping direct future investigations to with spots on the map of research in fairness. Document type: Part of book or chapter of book

Abstract

The TCP congestion control protocol is mainly designed for bandwidth symmetric paths. As two-way asymmetric connections will probably become common case in the future with the widespread use of ADSL, satellites and other high-speed technologies, it is important to make sure that congestion will be properly handled in these environments. To this end, we propose in this paper a new Adaptive Class-based Queuing mechanism called ACQ for handling two-way TCP traffic over links that exhibit bandwidth asymmetry. ACQ runs at the entry of the slow link and relies on two separate classes, one for ACK packets and one for Data packets. ACQ proposes to adapt the weights of both classes according to the crossing traffic in order to maximize some utility function defined by the user or the network operator. We show by simulations that our mechanism is able to reach a good utilization of the available resources, managing then to maximize the satisfaction of the user of such asymmetric connections. Document type: Part of book or chapter of book

Abstract

The problem of Minimum Congestion Hypergraph Embedding in a Cycle (MCHEC) is to embed the hyperedges of a hypergraph as paths in a cycle such that the maximum congestion (the maximum number of paths that use any single link in the cycle) is minimized. This problem has many applications, including minimizing communication congestions in computer networks and parallel computations. The MCHEC problem is NP-hard. We give a 1.8-approximation algorithm for the problem. This improves the previous 2-approximation results. The algorithm has the optimal O(mn) time for the hypergraph with m hyperedges and n nodes. Document type: Part of book or chapter of book