A differentiated optical services model for WDM networks

This article addresses the issues of scalable end-to-end QoS in metropolitan DWDM networks serving as transit networks for IP access networks. DWDM offering a few wavelengths has been deployed in the past in backbone networks to upgrade point-to-point transmission where sharing is based on coarse granularity. This type of DWDM backbone network, offering a few light-paths, provides no support for QoS services traversing the network. As DWDM networks with larger numbers of wavelengths penetrate the data-centric metro environment, specific IP service requirements such as priority restoration, scalability, dynamic provisioning of capacity and routes, and support for coarse-grain QoS capabilities will have to be addressed in the optical domain in order to achieve end-to-end QoS over a DWDM network. We propose a QoS service model in the optical domain called differentiated optical services (DoS) based on a set of optical parameters that captures the quality and reliability of the optical lightpath     

区分服务模型中的一种动态队列管理算法

在对区分服务模型和RED算法进行分析的基础上，提出了一种基于RED算法的动态队列管理算法。实验结果证明，我们提出的算法在不损害高优先级数据流量的情况下，能较好地实时调整各优先级的门限值，减少网络资源的消耗，提高网络资源的利用率。     

A scale database architecture for network services

A radical technology for databases, called the Datacycle architecture, which implements a relational model for network services and scales to support throughput of thousands of transactions per second is proposed. A set of data manipulation primitives useful in describing the logic network services is described. The use of the relational model together with an extended structured-query-language-like query language to describe 800 service, network automatic call distribution, and directory-assisted call completion services, is examined. The architectural constraints on the scalability of traditional database systems is reviewed, and an alternative, the Datacycle architecture is presented. The Datacycle approach exploits the bandwidth of fiber optics to circulate database contents among processing nodes (e.g. switching offices or other network elements) in a network, providing highly flexible access to data and controlling the administrative and processing overhead of coordinating changes to database contents. A prototype system operating in the laboratory is described. The feasibility of the Datacycle approach for both existing and future applications is considered     

Trustworthy Web services provisioning for differentiated customer services

With the number of e-Business applications dramatically increasing, a service level agreement (SLA) will play an important part in Web services. The SLA is a combination of several quality of services (QoS), such as security, performance, and availability, agreed between a customer and a service provider. Most existing research addresses only one of these QoS metrics. Furthermore, in the case of the response time defined as one of QoS metrics for performance, only the average time to process and complete a job is typically used. Moreover, customer requests often need to be distinguished, with different request characteristics and customer’s different service requirements. In this paper, we consider a set of computer resources used by a service broker to host enterprise applications for two classes of differentiated customer services subject to a service level agreement. We study three QoS metrics, namely, trustworthiness, a percentile response time, and availability. The percentile response time metric defines a value below which the end-to-end response time has to be for a given percent of time. We present an approach for resource optimization in such an environment that minimizes the total cost of computer resources while satisfying all these three QoS metrics in a trust-based resource provisioning problem which typically arises in Web services. We formulate the trust-based resource provisioning problem as an optimization problem under SLA constraints, and then solve it using an efficient numerical procedure.     

A routing architecture for mobile integrated services networks

A drawback of the conventional Internet routing architecture is that its route computation and packet forwarding mechanisms are poorly integrated with congestion control mechanisms. Any datagram offered to the network is accepted; routers forward packets on a best-effort basis and react to congestion only after the network resources have already been wasted. A number of proposals improve on this to support multimedia applications; a promising example is the Integrated Services Packet Network (ISPN) architecture. However, these proposals are oriented to networks with fairly static topologies and rely on the same conventional Internet routing protocols to operate. This paper presents a routing architecture for mobile integrated services networks in which network nodes (routers) can move constantly while providing end-to-end performance guarantees. In the proposed connectionless routing architecture, packets are individually routed towards their destinations on a hop by hop basis. A packet intended for a given destination is allowed to enter the network if and only if there is at least one path of routers with enough resources to ensure its delivery within a finite time. Once a packet is accepted into the network, it is delivered to its destination, unless resource failures prevent it. Each router reserves resources for each active destination, rather than for each source–destination session, and forwards a received packet along one of multiple loop-free paths towards the destination. The resources and available paths for each destination are updated to adapt to congestion and topology changes. This mechanism could be extended to aggregate dissimilar flows as well. This revised version was published online in June 2006 with corrections to the Cover Date.     

A policy framework for integrated and differentiated services inthe Internet

We examine the issues that arise in the definition, deployment, and management of policies related to QoS in an IP network. The article provides an overview of requirements for QoS policies, alternative policy architectures that can be deployed in a network, different protocols that can be used to exchange policy information, and exchange of policy information among different administrative domains. We discuss current issues being examined in IETF and other standards bodies, as well as issues explored in ongoing policy-related research at different universities and research laboratories     

A dynamic bandwidth allocation scheme for differentiated services in EPONs

Passive optical networks bring high-speed broadband access via fiber to the business, curb and home. Among various types of PONs, Ethernet PONs are gaining more and more attention since they are built on widely used Ethernet technology and can offer high bandwidth, low cost and broad services. EPONs use a point-to-multipoint topology, in which multiple optical network units share one uplink channel to transmit multimedia traffic to a control element, the optical line terminal. To avoid data collision on the shared uplink channel, a key issue in EPONs is a contention-free MAC protocol for the OLT to schedule the transmission order of different ONUs. In this article we first review some DBA schemes available in the literature, then propose a two-layer bandwidth allocation scheme that implements weight based priority for this need. To maximally satisfy the requests of all ONUs and provide differentiated services, an ONU is allowed to request bandwidth for all its available traffic, and all traffic classes proportionally share the bandwidth based on their instantaneous demands. The weight set for each class not only prevents high-priority traffic from monopolizing the bandwidth under heavy load but also ensures a minimum bandwidth allocated to each traffic class.     

A case for relative differentiated services and the proportionaldifferentiation model

Internet applications and users have very diverse quality of service expectations, making the same-service-to-all model of the current Internet inadequate and limiting. There is a widespread consensus today that the Internet architecture has to extended with service differentiation mechanisms so that certain users and applications can get better service than others at a higher cost. One approach, referred to as absolute differentiated services, is based on sophisticated admission control and resource reservation mechanisms in order to provide guarantees or statistical assurances for absolute performance measures, such as a minimum service rate or maximum end-to-end delay. Another approach, which is simpler in terms of implementation, deployment, and network manageability, is to offer relative differentiated services between a small number of service classes. These classes are ordered based on their packet forwarding quality, in terms of per-hop metrics for the queuing delays and packet losses, giving the assurance that higher classes are better than lower classes. The applications and users, in this context, can dynamically select the class that best meets their quality and pricing constraints, without a priori guarantees for the actual performance level of each class. The relative differentiation approach can be further refined and quantified using the proportional differentiation model. This model aims to provide the network operator with the “tuning knobs” for adjusting the quality spacing between classes, independent of the class loads. When this spacing is feasible in short timescales, it can lead to predictable and controllable class differentiation, which ore two important features for any relative differentiation model. The proportional differentiation model can be approximated in practice with simple forwarding mechanisms (packet scheduling and buffer management) that we describe     

A programmable architecture for the provision of hybrid services

The success of new service provision platforms will largely depend on their ability to blend with existing technologies. The advent of Internet telephony, although impressive, is unlikely to make telephone customers suddenly turn in favor of computers. Rather, customers display increasing interest in services that span multiple networks (especially Internet protocol-based networks and the telephone and cellular networks) and open new vistas. We refer to these services as hybrid services and propose an architecture for their provision. This architecture allows for programming the service platform elements (i.e., network nodes, gateways, control servers, and terminals) in order to include new service logics. We identify components that can be assembled to build these logics by considering a service as a composition of features such as address translation, security, call control, connectivity, charging, and user interaction. Generic service components are derived from the modeling of these features. We assure that our proposal can be implemented even in existing systems in return for slight changes. These systems are required to generate an event when a special service is encountered. The treatment of this event is handled by an object at a Java service layer. Java has been chosen for its platform-neutrality property and its embedded security mechanisms. Using our architecture, we design a hybrid closed user group service     

A control and management architecture supporting autonomic NFV services

Photonic Network Communications - The proposed control, orchestration and management (COM) architecture is presented from a high-level point of view; it enables the dynamic provisioning of services...     

A novel approach to provision differentiated services in survivable IP-over-WDM networks

IP-over-WDM networks are starting to replace legacy telecommunications infrastructure and they form a promising solution for next-generation networks (NGNs). Survivability of an IP-over-WDM network is gaining increasing interest from both the Internet research community and service providers (SPs). We consider a novel static bandwidth-provisioning algorithm to support differentiated services in a survivable IP-over-WDM network. We propose and investigate the characteristics of both integer linear program (ILP) and heuristic approaches to solve this problem. In the heuristic method, we propose backup reprovisioning to ensure network resilience against single-node or multiple-link failures. Illustrative examples compare and evaluate the performance of the two methods in terms of capacity-usage efficiency and computation time.     

A novel AWG-based WDM-PON architecture with full protection capability

The higher bandwidth utilization of wavelength-division-multiplexing passive optical networks (WDM-PONs) can be problematic if the link failure is not repaired in a timely manner since major data losses may occur in the event of link failure. Therefore, developing robust WDM-PON architectures with an effective protection capability is an essential task when designing optical access networks. Although the literature contains many proposals for WDM-PON protection schemes, the majority of these schemes protect either the feeder fibers or the distribution fibers, but not both. By exploiting the cyclic properties of the AWG and establishing appropriate interconnections between matched pairs of ONUs such that one ONU in the pair can use the distribution fiber assigned to its partner for backup purposes, the proposed scheme can protect both the feeder fibers and the distribution fibers through the designated protection streams in feeder fiber 3. Additionally, five operational modes of the proposed scheme are detailed with the proposed wavelength assignment scheme, the operational sequence, and the operation flow chart of decision circuit in the ONU/OLT. The analytical results have shown that the proposed scheme not only provides a full protection capability for WDM-PON networks, but also has a lower unavailability, a lower construction cost, and a reduced wavelength requirement than existing representative protection schemes. Finally, an analysis of the power budget and the recovery time has confirmed the practical feasibility of the proposed scheme.     

Dynamic core provisioning for quantitative differentiated services

Efficient network provisioning mechanisms that support service differentiation are essential to the realization of the Differentiated Services (DiffServ) Internet. Building on our prior work on edge provisioning, we propose a set of efficient dynamic node and core provisioning algorithms for interior nodes and core networks, respectively. The node provisioning algorithm prevents transient violations of service level agreements (SLA) by predicting the onset of service level violations based on a multiclass virtual queue measurement technique, and by automatically adjusting the service weights of weighted fair queueing schedulers at core routers. Persistent service level violations are reported to the core provisioning algorithm, which dimensions traffic aggregates at the network ingress edge. The core provisioning algorithm is designed to address the difficult problem of provisioning DiffServ traffic aggregates (i.e., rate-control can only be exerted at the root of any traffic distribution tree) by taking into account fairness issues not only across different traffic aggregates but also within the same aggregate whose packets take different routes through a core IP network. We demonstrate through analysis and simulation that the proposed dynamic provisioning model is superior to static provisioning for DiffServ in providing quantitative delay bounds with differentiated loss across per-aggregate service classes under persistent congestion and device failure conditions when observed in core networks.     

一种支持分级服务和最小带宽保证的改进TCP算法

本文提出了一种支持分级服务和最小带宽保证的改进TCP算法－DSAS－TCP，通过对TCP算中慢启动阈值和最小拥塞窗口的分级设置来使不同等级连接的平均吞吐量产生分级，并保证用户的最小带宽需求。通过理论分析和仿真实验验证了该算法的有效性。     

A unified wireless LAN architecture for real-time and non-real-timecommunication services

This paper addresses how to support both real-time and non-real-time communication services in a wireless LAN with dynamic time-division duplexed (D-TDD) transmission. With D-TDD, a frequency channel is time-shared for both downlink and uplink transmissions under the dynamic access control of the base station. The base station (1) handles uplink transmissions by polling mobiles in a certain order determined on a per-connection (per-message) basis for transmitting real-time (non-real-time) traffic from mobiles and (2) schedules the transmission of downlink packets. To handle location-dependent, time-varying, and bursty errors, we adopt the channel-state prediction, transmission deferment, and retransmission. We consider the problems of scheduling and multiplexing downlink packet transmissions, and polling mobiles for uplink transmissions depending on the channel state. We also establish conditions necessary to admit each new real-time connection by checking if the connection's delivery-delay bound can be guaranteed as long as the channel stays in good condition without compromising any of the existing guarantees. Last, the performance of the proposed protocol is evaluated to demonstrate how the protocol works and to study the effects of various parameters of the protocol     

Wireless and cellular architecture and services

Cellular architecture partitioning can improve the performance of telecommunications systems. The model proposed by the author allows for changing the cell size for different services and the number of users. The cell size that will ensure the best possible performance and quality of service can be derived by the model. The main task of a telecommunication system is call processing. This includes identifying incoming calls, establishing a communication path for the duration of the connection, and disconnecting the call after the conversation has ended. Call processing uses different components of the software architecture and involves processes and messages performing different functions and accessing various resources. In addition, the system requires administration and maintenance that also involves processes using different resources     

Application-level differentiated multimedia Web services usingquality aware transcoding

The ability of a Web service to provide low-latency access to its content is constrained by available network bandwidth. While providing differentiated quality of service (QoS) is typically enforced through network mechanisms, in this paper we introduce a robust mechanism for managing network resources using application-specific characteristics of Web services. We use transcoding to allow Web servers to customize the size of objects constituting a Web page, and hence the bandwidth consumed by that page, by dynamically varying the size of multimedia objects on a per-client basis. We leverage our earlier work on characterizing quality versus size tradeoffs in transcoding JPEG images to supply more information for determining the quality and size of the object to transmit. We evaluate the performance benefits of incorporating this information in a series of bandwidth management policies using realistic workloads and access scenarios to drive our system. The principal contribution of this paper is the demonstration that it is possible to use informed transcoding techniques to provide differentiated service and to dynamically allocate available bandwidth among different client classes, while delivering good quality of information content for all clients. We also show that it is possible to customize multimedia objects to the highly variable network conditions experienced by mobile clients in order to provide acceptable quality and latency depending on the networks used in accessing the service. We show that policies that aggressively transcode the larger images can produce images with quality factor values that closely follow the untranscoded base case while still saving as much as 150 kB. A transcoding policy that has knowledge of the characteristics of the link to the client can avoid as many as 40% of (unnecessary) transcodings