Availability of end-to-end ideal QoS in IP packet networks

Network processor technology has advanced to the point where high-precision time-based store-and-forward logic is readily incorporated into packet switches and routers. With appropriate scheduling, packets from multiple flows can be serviced without contending for link resources. Accordingly, packet flows traversing a network of switching elements can have both path and time determinacy attributes which support ideal end-to-end QoS (zero jitter, zero loss, acceptable end-to-end latency) for real-time UDP packet flows and guaranteed goodput for TCP flows. One approach to packing a network with a relatively large number of such deterministic flows, i.e. achieving high availability of the ideal QoS service in a network, uses precise buffering of packets at each switch, which introduces latency. This paper describes analysis methods for quantifying how much buffering may be necessary to achieve high (99.999%) availability. For typical network topologies the analysis shows that buffering latency requirements are very small compared to transport delays, even when the network is highly utilized with heterogeneous (e.g. voice, video, circuit emulation, and data) traffic. Actual physical implementations have empirically validated the analysis results as well as the scalability of the end-to-end, time-based forwarding approach and the end-to-end availability of ideal QoS services in IP packet networks.     

Coding- and interference-aware routing protocol in wireless networks

Network coding is considered as a promising technique to increase the bandwidth available in a wireless network. Many studies show that network coding can improve flow throughput only if an appropriate routing algorithm is used to identify paths with coding opportunities. Nevertheless, a good routing mechanism is very difficult to develop. Existing solutions either do not estimate the path bandwidth precisely enough or cannot identify the best path in some situations. In this paper, we describe our coding-aware routing protocol that provides a better path bandwidth estimate and is able to identify high throughput paths. Extensive NS2 simulations show that our protocol outperforms existing mechanisms.     

Pricing strategies for differentiated services content delivery networks

In order to reduce the user latency, the web sites disseminate some of their information to surrogate caches located closer to the users. We discuss a simple differentiated service type architecture for content delivery networks. A pricing scheme is next proposed to complement this architecture and provide fair service to the subscribed publishers. Then, we show that the suggested pricing scheme is also the optimal (revenue maximizing) pricing scheme for a monopolistic surrogate. We investigate the performance of the pricing scheme in a duopoly and show that under certain conditions the competition results in peering of the surrogates. Finally, we suggest methods to determine the optimal number of service classes offered to the users.     

Supporting multiple classes of services in IP over WDM ring network

In reference [1-2], the authors proposed a novel cartier preemption MAC protocol based on cartier sense multiple access schemes has been designed to supporting IP packets over all optical WDM MAN ring networks. Since the traditional IP provides the best effort service only, the issue of supporting IP packets with QoS transfer has become a crucial issue for multimedia transmission. We do so by addressing the priority-aware QoS model.     

IP网中约束路由的一种算法研究

Internet的迅猛发展对网络提出了更高的要求,而原有的最努力服务不能适应新的应用的需求。为了使Internet继续发展,必须能够提供有服务质量(QoS)保证的服务。IETF提出了几种服务模型和机制来满足用户的需求,比较典型的有集成服务模型、区分服务模型和流量工程。约束路由是流量工程中的一个重要工具。该文分析了延迟的主要组成部分,用M/M/1模型来分析通过节点的时间和节点负荷率的关系,通过限制各节点负荷率提出了一种新的约束路由算法,这种尝试性的算法对约束路由的研究具有一定的启发意义。     

An agent-based metric for quality of services over wireless networks

In a wireless LAN environment, clients tend to associate with the nearest access point (AP) which usually provides the strongest signal. However, this does not guarantee that users will receive the best quality of service (QoS) if the population sharing the network capacity were not considered. In other words, within the same access point, the more the population is, the less bandwidth each user will share, and the worse the quality of service will be. In this paper, we proposed an anticipative agent assistance (AAA) which is an agent-based metric for evaluating and managing the resource information of the wireless access points, computing the potential AP list, and providing clients with resource information of APs. We also propose a novel QoS feedback mechanism which allows users to promptly adjust the service quality with AAA according to the throughput and delay requirements. We evaluate the performance of our proposed method using the ns-2 simulator. Numerical results show that AAA achieves: (1) reduce the transmission delay, (2) increase the throughput, (3) improve the network utilization, (4) accommodate more users to access the networks, and (5) achieve load-balancing. Our metric is implementation feasible in various IEEE WLAN environments.     

An adaptive framework for 3D graphics over networks

Access to and transmission of 3D models over networks becomes increasingly popular. However, the performance and quality of access to remote 3D models strongly depends on system load conditions and the capabilities of the various system components, such as clients, servers, and interconnect. The network graphics framework (NGF) integrates various transmission methods for downloading 3D models in a client–server environment. The NGF automatically selects the optimal transmission method for a given pair of client and server, taking into account characteristics of the model to be transmitted, critical environment conditions, user preferences and the capabilities of the client and the server. The NGF aims to provide constant quality of service across different clients and under varying environment conditions.     

Call admission control and load balancing for voice over IP

IP networks are traditionally designed to support a best-effort service, with no guarantees on the reliable and timely delivery of packets. With the migration of real-time applications such as voice onto IP-based platforms, the existing IP network capabilities become inadequate to provide the quality-of-service (QoS) levels that the end-users are accustomed to. While new protocols such as DiffServ and MPLS allow some amount of traffic prioritization, guaranteed QoS requires call admission control. This paper reviews several possible implementations and shows simulation results for one promising method that makes efficient use of the network and is scalable to large networks.     

多约束QoS多播路由的模型和算法研究

随着高性能网络、移动网络及Internet的不断发展,具有QoS约束的多播路由技术已成为网络及分布式系统领域的一个重要研究课题。基于约束多播路由的目的在于鉴别一条路径满足QoS约束,然而,多加、乘约束的路由是一个NP-完全性问题。因此,快速的和精确的约束路由算法是少有的,甚至不存在。如此基于路由算法的需求导致众多的启发算法和一些少有的QoS算法的出现。文章描述了一种适用于研究QoS多播路由的网络模型,给出一个完全,简洁和公平地评价7个典型的基于多约束QoS多播路由算法,并且提供多约束路径算法的最坏情况下复杂性的比较。     

无线传感器网络适应QoS机制的网络模型

基于无线传感器网络服务质量(QoS)的特点,提出了一个独立于具体算法的、在点和边上都可加权的有向图网络模型,并用数学定义描述了QoS参数间的关系及服从的函数约束,使用该网络模型分析QoS路由的数学约束集并提出QoS路由选择策略。     

移动自组网基于动态簇的MAC协议与QoS路由

论文针对移动自组网提出了一种基于动态簇的MAC协议和QoS路由算法,使用全分布式动态簇生成算法实现了对网络拓扑的分簇与维护;利用正交编码原理和蜂窝小区技术实现了基于动态簇的MAC协议;融合资源预留、移动预测和后备路径技术实现了具有QoS保障的路由算法。仿真结果对比表明:在满足QoS条件下,它提高了路由效率。     

Generalized linear recursive networks: topological and routing properties

This paper presents a methodology for generalizing the class of linear recursive networks (LRN) reported by Hsu et al. [IEEE Trans Parallel Distrib Syst 1997; 8(7)]. The proposed generalization relaxes the restriction on the number of isomorphic subgraphs of LRNs, which is at most 1 by Hsu et al. [IEEE Trans Parallel Distrib Syst 1997; 8(7)]. Hence, our methodology permits the design of a communication topology of size n which satisfies the linear recurrence equation G_n(A)=a₁G_n−1(A)∪a₂G_n−2(A)∪?∪a_kG_n−k(A), with a_j being any non-negative integer for each j∈{1,2,…,k} and a₁>0. In addition, we address the problem of routing of messages in an generalized linear recursive network (GLRN). The paradigm of Fibonacci cubes (FCs) is used to demonstrate the proposed technique. FCs were introduced recently as an attractive alternative to the well-known hypercube model for interconnection networks.A generalized FC, referred to as a “Fibonacci graph” (FG) of size n, is composed of an arbitrary number of such graphs of size n−1 and size n−2.The structural advantage of GLRNs, in general, and FG, in particular, manifests itself in the following ways:

1.

They allow more choices to construct systems of various sizes.

2.

They emulate other topologies, such as hypercubes, trees, rings and meshes very efficiently.

The results of this paper have important applications e.g. in multitasking and job scheduling where a job is decomposed into a set of tasks and assigned to a subset of processors with specified interconnection topology.     

Integrated connection-level and packet-level QoS controls over wireless mesh networks

This paper focuses on integrating connection-level and packet-level QoS controls over wireless mesh network (WMN) to support applications with diverse QoS performance requirements. At the connection-level, the dynamic guard based prioritized connection admission control (DG-PCAC) provides prioritized admission with relative connection blocking probabilities and end-to-end deterministic minimum bandwidth allocation guarantees. DG-PCAC is enabled by dynamic guard based logical link configuration controls (LCCs), which provides relative differentiated capacity limits for prioritized admission classes. At the packet-level, the optimal rate delay scheduler (ORDS) dynamically allocates link bandwidth to the admitted flows of prioritized traffic classes; with the objective to minimize deviation from relative delay targets with minimum bandwidth guarantees according to traffic classes. Two realizations of the ORDS are presented, namely optimal scheduling policy via dynamic programming (DP) algorithm, and neural network (NN) based heuristic to alleviate computational complexity. Performance results show that the DG-PCAC enables consistent performance guarantees under non-stationary arrivals of connection requests. Performance results also show that the performance of the NN based scheduling heuristic approaches to that of the DP based optimal ORDS scheme.     

Strategy, networks and systems in the global translation services market

The globalisation of markets has led to an increased demand for language translation services that support and enable communication between economic partners. For example, technical documents, software systems, business documents and web sites all need to be translated into multiple languages for individual national markets, and the information that they contain changes periodically. This paper sets out a theoretical framework that describes the architectures of business processes within and between separate firms that are used to support the delivery and management of services. This is done by coordinating the fit between externally generated problem complexity, from customers, and the internally generated complexity of different potential network configuration solutions. The theoretical framework is an architecture of how complexity is generated and managed at the different structural levels and across the different processual stages of an industry. A case study of thebigword, a major international translation services company, illustrates how the framework is applied in practice. The case study analyses the implementation of an electronic market platform which enables the coordination of the different stakeholders involved in the translation services market. These stakeholders include translators, translation services companies and their clients in a global business network.     

OPQR-G: algorithm for efficient QoS partition and routing in multiservice IP networks

This paper considers the combined problem of optimal QoS partition and routing (problem QPQR-G) for a QoS framework in which a performance dependent cost function is associated with each network element and the QoS metric is additive (e.g. delay, jitter). This problem has been addressed in the context of unicast connections and multicast trees only. Here we consider the problem for a more general case of a multicommodity flow network. Also, it is assumed that the performance dependent cost functions are non-increasing and are of general integer type. The goal is to determine primary paths between the origin and destination (OD) pairs and QoS partitions on the links so that the overall cost in the network is minimised while all OD pair QoS requirements are satisfied. As the problem is NP-complete, we concentrate on the development of an efficient heuristic algorithm. In addition, two LP-based algorithms were developed, that use the optimisation tool ILOG™ CPLEX 7.1 LP for solving the problem OPQR-G. The numerical results obtained for various test network scenarios are very close to the optimal. The problem addressed in this paper provides the basis for the solution of many interesting and practical engineering problems, such as dimensioning and admission control/resource reservation in IP networks that support service differentiation.     

On-line joint QoS routing and channel assignment in multi-channel multi-radio wireless mesh networks

We study the problem of on-line joint QoS routing and channel assignment for performance optimization in multi-channel multi-radio wireless mesh networks, which is a fundamental issue in supporting quality of service for emerging multimedia applications. To our best knowledge, this is the first time that the problem is addressed. Our proposed solution is composed of a routing algorithm that finds up to k but not necessarily feasible paths for each demand and an on-demand channel (re)assignment algorithm that adapts network resources to maintain feasibility of one of the paths. We also study the problem of obtaining an upper bound on the network performance. First, we consider an artificial version of the problem, in which all demands arrive at the same time, and formulate it as a mixed integer linear programming model. To tackle the complexity of the model, it is relaxed that provides a tight upper bound while improves solution time up to 3.0e+5 times. Then, we model the original problem by extending the relaxed model to consider dynamic demands, it leads to a huge model; thus, we develop another model, which is equivalent to the first one and is decomposable. It is broken down by a decomposition algorithm into subproblems, which are solved sequentially. Our extensive simulations show that the proposed solution has comparable performance to the bound obtained from the decomposition algorithm; it efficiently exploits available channels, and needs very few radios per node to achieve high network performance.     

IP路由查找和报文分类模型研究

IP路由查找和报文分类作为路由器转发能力和提供高性能区分服务能力的关键因素,是当前路由器转发性能乃至整个网络性能的主要瓶颈。文章以IP路由查找和报文分类问题为研究对象,从空间几何的角度探究其本质,建立了相应数学模型MDCM,并以此为基础,讨论了各类搜索算法在IP路由查找和报文分类问题求解的优缺点,为研究和设计高性能的IP路由查找和报文分类算法提供重要指导。     

An accurate performance model for network-on-chip and multicomputer interconnection networks

In this paper, we present a mathematical background for a new approach for performances modeling of interconnection networks, based on analyzing the packet blocking and waiting time spent in each channel passing through all possible paths in the channel dependency graph. We have proposed a new, simple and very accurate analytical model for deterministic routing in wormhole networks, which is general in terms of the network topology and traffic distribution. An accurate calculation of the variance of the service time has been developed, which overcomes the rough approximation used, as a rule, in the existing models. The model supports two-dimensional mesh topologies, widely used in network-on-chip architectures, and multidimensional topologies, popular in multicomputer architectures. It is applicable even for irregular topologies and arbitrary application-specific traffic. Results obtained through simulation show that the model achieves a high degree of accuracy.