Quality of Service Routing is at present an active and remarkable research area, since most emerging network services require specialized Quality of Service (QoS) functionalities that cannot be provided by the current QoS-unaware routing protocols. The provisioning of QoS based network services is in general terms an extremely complex problem, and a significant part of this complexity lies in the routing layer. Indeed, the problem of QoS Routing with multiple additive constraints is known to be NP-hard. Thus, a successful and wide deployment of the most novel network services demands that we thoroughly understand the essence of QoS Routing dynamics, and also that the proposed solutions to this complex problem should be indeed feasible and affordable. This article surveys the most important open issues in terms of QoS Routing, and also briefly presents some of the most compelling proposals and ongoing research efforts done both inside and outside the E-Next Community to address some of those issues. q

Abstract. This paper proposes a novel and incremental approach to InterDomain QoS Routing. Our approach is to provide a completely distributed Overlay Architecture and a routing layer for dynamic QoS provisioning, and to use QoS extensions and Traffic Engineering capabilities of the underlying BGP layer for static QoS provisioning. Our focus is mainly on influencing how traffic is exchanged among non-directly connected multi-homed Autonomous Systems based on specific QoS parameters. We provide evidence supporting the feasibility of our approach by means of simulation.

Smart route control is being increasingly used as a way to dynamically improve the end-to-end performance of the outbound traffic of multihomed stub domains. However, all the solutions available at present have in common two drawbacks which are key motivations for this work. First, all solutions are standalone, so no routing control interactions exist between the domains sourcing and sinking the traffic. The consequences of this lack of interactions are quite coarse route control over the outbound traffic from the domains, and the inability to smartly control how traffic flows into the domains. The second drawback is that all available solutions behave in a fully selfish way, that is, they operate without considering the effects of their decisions in the performance of the network. Given these limitations, we propose to extend the existing route control model from standalone and selfish to a cooperative and social route control model. Our main contribution in this paper is to show that when several route controllers compete for the same network resources, the conventional ones are outperformed by those using a cooperative and social approach and this becomes especially noticeable as the network utilization increases. Our results reveal that it is possible to reduce the frequency of traffic relocations by more than a 50% on average and still obtain slightly better end-to-end traffic performance for delay-sensitive applications. A key advantage is that our extensions can be installed and used today by simply performing software upgrades to any of the existing route control solutions.

56 0890-8044/08/$25.00 © 2008 IEEE oday, the vast majority of the communications on the Internet are between nodes located in non-transit (i.e., stub) networks. Stub networks are primarily composed of medium and large enterprise customers, universities, public administrations, content service providers (CSPs), and small Internet service providers (ISPs). These networks exploit a widespread practice called multihoming, which consists of using multiple external links to connect to different transit providers. By increasing their connectivity to the Internet, stub networks potentially can obtain several benefits, especially in terms of resilience, cost, and traffic performance [1]. These are described as potential benefits because multihoming per se cannot improve any resilience, cost, and traffic performance. Accordingly, multihomed stub networks require additional mechanisms to achieve these improvements. In particular, when an automatic mechanism actively optimizes the cost and end-to-end performance of the traffic routed among different links connecting a multihomed stub network to the Internet, it is referred to as intelligent route control (IRC).During the last few years, IRC has attracted significant interest in both the research and the commercial fields. Several vendors are developing and offering IRC solutions [2][3][4] that increasingly are being adopted by multihomed stub networks. Most available IRC solutions follow the same principle, that is, they dynamically shift part of the egress traffic of a multihomed subscriber from one of its ISPs to another, using measurement-driven path switching techniques. IRC systems operate in relatively short timescales -even reaching switching frequencies on the order of a few seconds -allowing IRC users to balance cost and performance criteria according to the priority and requirements of their applications.Despite these strengths, IRC practices have one major weakness, that is, they try to achieve a set of local objectives individually without considering the effects of their decisions on the performance of the network. Recently, it was discovered that in a competitive environment, IRC systems actually can cause significant performance degradation rather than improvement. In [5], the authors show that persistent oscillations can occur when independent controllers become synchronized due to a considerable overlap in their measurement time windows. To avoid synchronization issues, the authors propose randomized IRC strategies and empirically show that the oscillations disappear after introducing a random component in the route control decision.It is important to note that although randomization offers a straightforward mechanism to mitigate the oscillations, it cannot guarantee global stability. This issue raises concerns given the proliferation of IRC products because as the number of interfering IRC systems increases, randomization becomes AbstractMultihomed subscribers are increasingly adopting intelligent route control solutions to optimize the cost and end-to-en...