Dynamic buffer management policy for shared memory packet switches by employing per-queue thresholds

One of the main problems concerning high-performance communications networks is the unavoidable congestion in network nodes. Network traffic is normally characterised as "bursty", which may use up network resources during peak periods. As a consequence end-user applications are subject to end-to-end delays and disruptions. Simultaneous transmission of packets on a finite bandwidth channel might result in contentions, where one or more packets are refrained from entering the transmission channel resulting in packet losses. Hence, the motivations of this thesis are two-fold: investigation and evaluation of switch architectures with electronic and optical buffers, and the development and evaluation of an improved dynamic threshold policy for shared memory switch architecture. In this work, switch architectures based on modular designs are evaluated, with simulation results showing that modular switch structures, i.e. multistage interconnection networks with optical delay line buffers, offer packet loss rate, throughput and average delay time similar to their electronic counterparts. Such optical architectures emulate prime features of shared memory switch architecture under general traffic conditions. Although the shared memory switch architecture is superior to other buffering approaches, but its performance is inadequate under imbalanced input traffic. Here its limiting features are investigated by means of numerical analysis. Different buffer management schemes, namely static thresholds, dynamic thresholds, pre-emptive, adaptive control, are investigated by using the Markov simulation model. An improved dynamic buffer management policy, decay function threshold (DFT) policy, is proposed and it is compared with the dynamic thresholds (DT), partial sharing partial partitioning (PSPP) and dynamic queue thresholds (DQT) buffer management policies by using bursty traffic source models, such as interrupted Poisson process (IPP), by means of simulations. Simulation results show that proposed policy is as good as well-known dynamic thresholds policy in the presence of best-effort traffic and offers improved packet loss performance when multicast traffic is considered. An integration framework for dynamic buffer management and bandwidth scheduling is also presented in this study. This framework employs loosely coupled buffer management and scheduling (weighted round robin, weighted fair queueing etc.) providing support for quality of service traffic. Conducted tests show that this framework matches the best-effort packet loss performance of dynamic thresholds policy

Datacenter Traffic Control: Understanding Techniques and Trade-offs

Datacenters provide cost-effective and flexible access to scalable compute and storage resources necessary for today's cloud computing needs. A typical datacenter is made up of thousands of servers connected with a large network and usually managed by one operator. To provide quality access to the variety of applications and services hosted on datacenters and maximize performance, it deems necessary to use datacenter networks effectively and efficiently. Datacenter traffic is often a mix of several classes with different priorities and requirements. This includes user-generated interactive traffic, traffic with deadlines, and long-running traffic. To this end, custom transport protocols and traffic management techniques have been developed to improve datacenter network performance. In this tutorial paper, we review the general architecture of datacenter networks, various topologies proposed for them, their traffic properties, general traffic control challenges in datacenters and general traffic control objectives. The purpose of this paper is to bring out the important characteristics of traffic control in datacenters and not to survey all existing solutions (as it is virtually impossible due to massive body of existing research). We hope to provide readers with a wide range of options and factors while considering a variety of traffic control mechanisms. We discuss various characteristics of datacenter traffic control including management schemes, transmission control, traffic shaping, prioritization, load balancing, multipathing, and traffic scheduling. Next, we point to several open challenges as well as new and interesting networking paradigms. At the end of this paper, we briefly review inter-datacenter networks that connect geographically dispersed datacenters which have been receiving increasing attention recently and pose interesting and novel research problems.Comment: Accepted for Publication in IEEE Communications Surveys and Tutorial

The Octopus switch

This chapter1 discusses the interconnection architecture of the Mobile Digital Companion. The approach to build a low-power handheld multimedia computer presented here is to have autonomous, reconfigurable modules such as network, video and audio devices, interconnected by a switch rather than by a bus, and to offload as much as work as possible from the CPU to programmable modules placed in the data streams. Thus, communication between components is not broadcast over a bus but delivered exactly where it is needed, work is carried out where the data passes through, bypassing the memory. The amount of buffering is minimised, and if it is required at all, it is placed right on the data path, where it is needed. A reconfigurable internal communication network switch called Octopus exploits locality of reference and eliminates wasteful data copies. The switch is implemented as a simplified ATM switch and provides Quality of Service guarantees and enough bandwidth for multimedia applications. We have built a testbed of the architecture, of which we will present performance and energy consumption characteristics

Quality of Service over Specific Link Layers: state of the art report

The Integrated Services concept is proposed as an enhancement to the current Internet architecture, to provide a better Quality of Service (QoS) than that provided by the traditional Best-Effort service. The features of the Integrated Services are explained in this report. To support Integrated Services, certain requirements are posed on the underlying link layer. These requirements are studied by the Integrated Services over Specific Link Layers (ISSLL) IETF working group. The status of this ongoing research is reported in this document. To be more specific, the solutions to provide Integrated Services over ATM, IEEE 802 LAN technologies and low-bitrate links are evaluated in detail. The ISSLL working group has not yet studied the requirements, that are posed on the underlying link layer, when this link layer is wireless. Therefore, this state of the art report is extended with an identification of the requirements that are posed on the underlying wireless link, to provide differentiated Quality of Service

Cross-layer design of multi-hop wireless networks

MULTI -hop wireless networks are usually defined as a collection of nodes equipped with radio transmitters, which not only have the capability to communicate each other in a multi-hop fashion, but also to route each others’ data packets. The distributed nature of such networks makes them suitable for a variety of applications where there are no assumed reliable central entities, or controllers, and may significantly improve the scalability issues of conventional single-hop wireless networks. This Ph.D. dissertation mainly investigates two aspects of the research issues related to the efficient multi-hop wireless networks design, namely: (a) network protocols and (b) network management, both in cross-layer design paradigms to ensure the notion of service quality, such as quality of service (QoS) in wireless mesh networks (WMNs) for backhaul applications and quality of information (QoI) in wireless sensor networks (WSNs) for sensing tasks. Throughout the presentation of this Ph.D. dissertation, different network settings are used as illustrative examples, however the proposed algorithms, methodologies, protocols, and models are not restricted in the considered networks, but rather have wide applicability. First, this dissertation proposes a cross-layer design framework integrating a distributed proportional-fair scheduler and a QoS routing algorithm, while using WMNs as an illustrative example. The proposed approach has significant performance gain compared with other network protocols. Second, this dissertation proposes a generic admission control methodology for any packet network, wired and wireless, by modeling the network as a black box, and using a generic mathematical 0. Abstract 3 function and Taylor expansion to capture the admission impact. Third, this dissertation further enhances the previous designs by proposing a negotiation process, to bridge the applications’ service quality demands and the resource management, while using WSNs as an illustrative example. This approach allows the negotiation among different service classes and WSN resource allocations to reach the optimal operational status. Finally, the guarantees of the service quality are extended to the environment of multiple, disconnected, mobile subnetworks, where the question of how to maintain communications using dynamically controlled, unmanned data ferries is investigated

Dynamic buffer management policy for shared memory packet switches by employing per-queue thresholds

One of the main problems concerning high-performance communications networks is the unavoidable congestion in network nodes. Network traffic is normally characterised as "bursty", which may use up network resources during peak periods. As a consequence end-user applications are subject to end-to-end delays and disruptions. Simultaneous transmission of packets on a finite bandwidth channel might result in contentions, where one or more packets are refrained from entering the transmission channel resulting in packet losses. Hence, the motivations of this thesis are two-fold: investigation and evaluation of switch architectures with electronic and optical buffers, and the development and evaluation of an improved dynamic threshold policy for shared memory switch architecture. In this work, switch architectures based on modular designs are evaluated, with simulation results showing that modular switch structures, i.e. multistage interconnection networks with optical delay line buffers, offer packet loss rate, throughput and average delay time similar to their electronic counterparts. Such optical architectures emulate prime features of shared memory switch architecture under general traffic conditions. Although the shared memory switch architecture is superior to other buffering approaches, but its performance is inadequate under imbalanced input traffic. Here its limiting features are investigated by means of numerical analysis. Different buffer management schemes, namely static thresholds, dynamic thresholds, pre-emptive, adaptive control, are investigated by using the Markov simulation model. An improved dynamic buffer management policy, decay function threshold (DFT) policy, is proposed and it is compared with the dynamic thresholds (DT), partial sharing partial partitioning (PSPP) and dynamic queue thresholds (DQT) buffer management policies by using bursty traffic source models, such as interrupted Poisson process (IPP), by means of simulations. Simulation results show that proposed policy is as good as well-known dynamic thresholds policy in the presence of best-effort traffic and offers improved packet loss performance when multicast traffic is considered. An integration framework for dynamic buffer management and bandwidth scheduling is also presented in this study. This framework employs loosely coupled buffer management and scheduling (weighted round robin, weighted fair queueing etc.) providing support for quality of service traffic. Conducted tests show that this framework matches the best-effort packet loss performance of dynamic thresholds policy.EThOS - Electronic Theses Online ServiceGBUnited Kingdo