We consider the problem of providing service guarantees in a high-speed packet switch. As basic requirements, the switch should be scalable to high speeds per port, a large number of ports and a large number of traffic flows with independent guarantees. Existing scalable solutions are based on Virtual Output Queuing, which is computationally complex when required to provide service guarantees for a large number of flows. We present a novel architecture for packet switching that provides support for such service guarantees. A cost-effective fabric with small external speedup is combined with a feedback mechanism that enables the fabric to be virtually lossless, thus avoiding packet drops indiscriminate of flows. Through analysis and simulation, we show that this architecture provides accurate support for service guarantees, has low computational complexity and is scalable to very high port speeds.
In recent years, these potential scalability concerns have been addressed by implementing a very small number of independent service guarantees. Under the Differentiated Services framework @cite_12 , flows are aggregated in @math classes, and service guarantees are offered for classes. The downside is that the realized QoS per flow has a lower level of assurance (higher probability of violating the desired service level) than the QoS per aggregate @cite_9 , @cite_1 . Moreover, recently proposed VPN and VLAN services @cite_11 , @cite_17 require per-VPN or VLAN QoS guarantees. All the above are arguments in favor of implemeting a number of independent service guarantees per port much larger than six.
@cite_11 @cite_9 @cite_1 @cite_12 @cite_17
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The paper addresses the issue of providing Quality of Service (QoS) guarantees in the Internet. After a brief discussion of Internet traffic characteristics, we consider the possibility of performing multiplexing with predictable performance for stream and elastic traffic using open–loop and closed–loop control, respectively. QoS depends essentially on providing sufficient capacity to handle expected demand. We argue that flow awareness is additionally necessary to ensure that traffic is directed over routes with available capacity and to avoid congestion collapse in case of overload. Proposed flow–aware controls allow simple volume–based charging and the development of an economic model similar to that of the telephone network. Providing differentiated Quality of Service (QoS) over unreliable wireless channels is an important challenge for supporting several future applications. We analyze a model that has been proposed to describe the QoS requirements by four criteria: traffic pattern, channel reliability, delay bound, and throughput bound. We study this mathematical model and extend it to handle variable bit rate applications. We then obtain a sharp characterization of schedulability vis-a-vis latencies and timely throughput. Our results extend the results so that they are general enough to be applied on a wide range of wireless applications, including MPEG Variable-Bit-Rate (VBR) video streaming, VoIP with differentiated quality, and wireless sensor networks (WSN). Two major issues concerning QoS over wireless are admission control and scheduling. Based on the model incorporating the QoS criteria, we analytically derive a necessary and sufficient condition for a set of variable bit-rate clients to be feasible. Admission control is reduced to evaluating the necessary and sufficient condition. We further analyze two scheduling policies that have been proposed, and show that they are both optimal in the sense that they can fulfill every set of clients that is feasible by some scheduling algorithms. The policies are easily implemented on the IEEE 802.11 standard. Simulation results under various settings support the theoretical study. We propose a novel approach to QoS for real-time traffic over wireless mesh networks, in which application layer characteristics are exploited or shaped in the design of medium access control. Specifically, we consider the problem of efficiently supporting a mix of Voice over IP (VoIP) and delay-insensitive traffic, assuming a narrowband physical layer with CSMA CA capabilities. The VoIP call carrying capacity of wireless mesh networks based on classical CSMA CA (e.g., the IEEE 802.11 standard) is low compared to the raw available bandwidth, due to lack of bandwidth and delay guarantees. Time Division Multiplexing (TDM) could potentially provide such guarantees, but it requires fine-grained network-wide synchronization and scheduling, which are difficult to implement. In this paper, we introduce Sticky CSMA CA, a new medium access mechanism that provides TDM-like performance to real-time flows without requiring explicit synchronization. We exploit the natural periodicity of VoIP flows to obtain implicit synchronization and multiplexing gains. Nodes monitor the medium using the standard CSMA CA mechanism, except that they remember the recent history of activity in the medium. A newly arriving VoIP flow uses this information to grab the medium at the first available opportunity, and then sticks to a periodic schedule, providing delay and bandwidth guarantees. Delay-insensitive traffic fills the gaps left by the real-time flows using novel contention mechanisms to ensure efficient use of the leftover bandwidth. Large gains over IEEE 802.11 networks are demonstrated in terms of increased voice call carrying capacity (more than 100 in some cases). We briefly discuss extensions of these ideas to a broader class of real-time applications, in which artificially imposing periodicity (or some other form of regularity) at the application layer can lead to significant enhancements of QoS due to improved medium access. Abstract This paper studies the quality of service (QoS) provision problem in noncooperative networks where applications or users are selfish and routers implement generalized processor sharing based packet scheduling. We formulate a model of QoS provision in noncooperative networks where users are given the freedom to choose both the service classes and traffic volume allocated, and heterogenous QoS preferences are captured by a user's utility function. We present a comprehensive analysis of the noncooperative multi-class QoS provision game, giving a complete characterization of Nash equilibria and their existence criteria, and show under what conditions they are Pareto- and system-optimal. We show that, in general, Nash equilibria need not exist, and when they do exist, they need not be Pareto- nor system-optimal. For certain “resource-plentiful” systems, however, we show that the world indeed can be nice with Nash equilibria, Pareto optima, and system optima collapsing into a single class. We study the problem of facilitating effective QoS in systems with multi-dimensional QoS vectors containing both mean- and burstiness-related QoS measures. We extend the game-theoretic analysis to multi-dimensional QoS vector games and show under what conditions the aforementioned results carry over.