Negotiated disk admission control in video streaming

A novel soft-quality of service framework for continuous media servers, which provides a dynamic and adaptive disk admission control and scheduling algorithm, is presented. Using this framework, the number of simultaneously running clients for video servers could be increased, and better resource utilisation under heavy communication traffic requirements could be ensured     

Videoconferencing on the Internet

This paper describes the INRIA videoconferencing system (IVS), a low bandwidth tool for real-time video between workstations on the Internet using UDP datagrams and the IP multicast extension. The video coder-decoder (codec) is a software implementation of the ITU-T recommendation H.261 originally developed for the integrated services digital network (ISDN). Our focus is on adapting this codec for the Internet environment. We propose a packetization scheme, an error control scheme and an output rate control scheme that adapts the image coding process based on network conditions. This work shows that it is possible to maintain videoconferences with reasonable quality across packet-switched networks without requiring special support from the network such as resource reservation or admission control     

Web server support for tiered services

The evolving needs of conducting commerce using the Internet requires more than just network quality of service mechanisms for differentiated services. Empirical evidence suggests that overloaded servers can have significant impact on user perceived response times. Furthermore, FIFO scheduling done by servers can eliminate any QoS improvements made by network-differentiated services. Consequently, server QoS is a key component in delivering end to end predictable, stable, and tiered services to end users. This article describes our research and results for WebQoS, an architecture for supporting server QoS. We demonstrate that through classification, admission control, and scheduling, we can support distinct performance levels for different classes of users and maintain predictable performance even when the server is subjected to a client request rate that is several times greater than the server's maximum processing rate     

The Tenet real-time protocol suite: design, implementation, andexperiences

Many future applications will require guarantees on network performance, such as bounds on throughput, delay, delay jitter, and reliability. To address this need, the authors have designed, simulated, and implemented a suite of network protocols to support real-time channels (network connections with mathematically provable performance guarantees). The protocols, which constitute the prototype Tenet real-time protocol suite (Suite 1), run on a packet-switching internetwork and can coexist with the popular Internet protocol suite. The authors rely on the use of connection-oriented communication, per-channel admission control, channel rate control, and priority scheduling. This protocol suite is the first set of transport and network-layer communication protocols that can transfer real-time streams with guaranteed quality in packet-switching internetworks. The authors have performed a number of experiments and demonstrations on multiple platforms using continuous-media loads (particularly video). The results show that the approach is both feasible and practical to build, and that it can successfully provide performance guarantees to real-time applications. The paper describes the design and implementation of, the suite, the experiments performed, and some of the lessons learned     

A Novel Probability-Based Handoff Strategy for Multimedia LEO Satellite Communications

A novel bandwidth allocation strategy and a connection admission control technique arc proposed to improve the utilization of network resource and provide the network with better quality of service （QoS） guarantees in multimedia low earth orbit （LEO） satellite networks. Our connection admission control scheme, we call the probability based dynamic channel reservation strategy （PDR）, dynamically reserves bandwidth for real-time services based on their handoff probability. And the reserved bandwidth for real-time handoff connection can also be used by new connections under a certain probability determined by the mobility characteristics and bandwidth usage of the system. Simulation results show that our scheme not only lowers the call dropping probability （CDP） for Class I real-time service but also maintains the call blocking probability （CBP） to certain degree. Consequently, the scheme can offer very low CDP for rcal-time connections while keeping resource utilization high.     

Cost-Effective Deployment of Bandwidth Partitioning in Broadband Networks

We consider the issue of bandwidth partitioning in a multi-rate broadband network. Requests for a number of different types of connection are offered to the network. For the purposes of connection admission and resource allocation, we assume that it is possible to allocate an effective bandwidth to a single connection of each type. The network manager has the problem of implementing an admission control scheme to maximise the profit earned from the network. Our focus here is the extent to which it is a good idea to partition the bandwidth on the physical links to form reserved end-to-end logical links corresponding to the origin–destination pairs. It is clear that implementation of such partitioning will lead to a loss of multiplexing opportunities. However, in a network with end-to-end logical links, costs related to overhead such as route selection, admission control and signalling may be much reduced. This effect may outweigh the loss of revenue due to missing out on multiplexing opportunities. We investigate the nature of this trade-off, by designing optimal or near-optimal partitioned networks using efficient algorithms for finding routes and allocating bandwidth to end-to-end logical links on a fixed underlying physical network. We then calculate the net rate of earning profit under each of the schemes as a function of the ratio of overhead costs to call revenue. Our conclusion is that it is cost-effective to partition bandwidth under a variety of realistic assumptions about revenue rates and overhead costs.     

Media Streaming With Network Diversity

Today's packet networks including the Internet offer an intrinsic diversity for media distribution in terms of available network paths and servers or information sources. Novel communication infrastructures such as ad hoc or wireless mesh networks use network diversity to extend their reach at low cost. Diversity can bring interesting benefits in supporting resource greedy applications such as media streaming services, by aggregation of bandwidth and computing resources. Typically, overlay network architectures compensate for lack of quality-of-service guarantees in the network by introducing redundancy in the media delivery system through network diversity. They can support efficient multimedia services when routing, coding, and scheduling algorithms are able to adapt to both the media information and the dynamic network status. This paper presents an overview of the distributed streaming solutions that profit from network diversity in order to improve the quality of multimedia applications. We discuss the coding techniques used for adaptive and flexible media streaming with network diversity. We describe the problem of media streaming with path diversity and focus on routing, path computation, and packet scheduling problems in multipath networks. Then, the advantages of server or source peer diversity in collaborative streaming solutions are discussed. Lastly, we present an overview of wireless mesh networks and focus on the typical constraints imposed by these novel communication models on media streaming with network diversity.     

Group priority scheduling

We present an end-to-end delay guarantee theorem for a class of guaranteed deadline (GD) servers. The theorem can be instantiated to obtain end-to-end delay bounds for a variety of source control mechanisms and GD servers. We then propose the idea of group priority, and specialize the theorem to a subclass of GD servers that use group priority in packet scheduling. With the use of group priority, the work of packet schedulers can be substantially reduced. We work out a detailed example, for the class of burst scheduling networks, to illustrate how group sizes can be designed such that the worst case end-to-end delay of application data units in a real-time flow is unaffected by the use of group priority. Group priority also can be used in packet schedulers that provide integrated services (best effort as well as real-time services) to achieve statistical performance gains, which we illustrate with empirical results from simulation experiments     

A scheduling application for WDM optical networks

Optical networking using WDM technology has matured considerably, and commercial WDM network equipment and WDM network control and management prototypes have appeared. To use such a network efficiently, a scheduling facility and its enabling mechanisms have to be provided. This scheduling facility should be integrated to interoperate with the rest of the network control and management software such as connection manager or signaling daemon. We present a scheduling application to address this need. The architecture for the application and its key components are presented. Agent-related enabling mechanisms are introduced to monitor the optical signal quality and collect performance measurements. A resource broker is used to manage the communication and interoperability between agents and the application. An event service is developed to decouple the communication between the agents and the scheduling application, and to enable the communication among the agents themselves. The scheduling application consists of the quality of signal information and threshold objects, current network usage, history data module, scheduling module, and access to a performance database. To provide traffic control and high network resource utilization, the application is equipped with wavelength scheduling algorithms. An experimental study for the basic scheduling algorithms has been conducted over the MONET DC network.     

Real-time server-based communication with CAN

This paper investigates the concept of share-driven scheduling of networks using servers with real-time properties. Share-driven scheduling provides fairness and bandwidth isolation between predictable as well as unpredictable streams of messages on the network. The need for this kind of scheduled real-time communication network is high in applications that have requirements on flexibility, both during development for assigning communication bandwidth to different applications, and during run-time to facilitate dynamic addition and removal of system components. We illustrate the share-driven scheduling concept by applying it to the popular controller area network (CAN). We propose a scheduling mechanism that we call simple server-scheduled CAN (S/sup 3/-CAN), for which we also present an associated timing analysis. Additionally, we present a variant of S/sup 3/-CAN called periodic server-scheduled CAN (PS/sup 2/-CAN), which for some network configurations gives lower worst-case response-times than S/sup 3/-CAN. Also for this improvement, a timing analysis is presented. Moreover, we use simulation to evaluate the timing performance of both S/sup 3/-CAN and PS/sup 2/-CAN, comparing them with other scheduling mechanisms.     

边缘算力网络中智能算力感知路由分配策略研究

增强现实、自动驾驶、智慧城市、工业互联网等新型业务应用对网络算力的需求逐渐增强,然而,边缘算力网络系统面临着网络共存的问题——负载不均衡,导致一部分边缘服务器无法满足业务应用的处理需求,另一部分边缘服务器的算力资源处于空闲状态.为了高效协同地感知利用泛在、异构的算力资源,提升6G通信网络的内生感知和算力自适应能力,急需...     

iDSRT: Integrated Dynamic Soft Real-time Architecture for Critical Infrastructure Data Delivery over WLAN

The real-time control data delivery system of the Critical Infrastructure (i.e. SCADA—Supervisory Control and Data Acquisition system) is important because appropriate decisions cannot be made without having data delivered in a timely manner. Because these applications use multiple heterogeneous resources such as CPU, network bandwidth and storage, they call for an integrated and coordinated real-time scheduling across multiple resources to meet end-to-end deadlines. We present a design and implementation of iDSRT—an integrated dynamic soft real-time system to provide fine-grained end-to-end delay guarantees over WLAN. iDSRT takes the deadline partitioning approach: end-to-end deadlines are partitioned into multiple sub-deadlines for CPU scheduling and network scheduling. It integrates three important schedulers: task scheduler, packet scheduler and node scheduler to achieve global coordination. We validate iDSRT in Linux and evaluate it in an experimental SCADA test-bed. The results are promising and show that iDSRT can successfully achieve soft real-time guarantees in SCADA system with very low packet loss rate compared to available commodity best-effort systems.     

Static Security Optimization for Real-Time Systems

An increasing number of real-time applications like railway signaling control systems and medical electronics systems require high quality of security to assure confidentiality and integrity of information. Therefore, it is desirable and essential to fulfill security requirements in security-critical real-time systems. This paper addresses the issue of optimizing quality of security in real-time systems. To meet the needs of a wide variety of security requirements imposed by real-time systems, a group-based security service model is used in which the security services are partitioned into several groups depending on security types. While services within the same security group provide the identical type of security service, the services in the group can achieve different quality of security. Security services from a number of groups can be combined to deliver better quality of security. In this study, we seamlessly integrate the group-based security model with a traditional real-time scheduling algorithm, namely earliest deadline first (EDF). Moreover, we design and develop a security-aware EDF schedulability test. Given a set of real-time tasks with chosen security services, our scheduling scheme aims at optimizing the combined security value of the selected services while guaranteeing the schedulability of the real-time tasks. We study two approaches to solve the security-aware optimization problem. Experimental results show that the combined security values are substantially higher than those achieved by alternatives for real-time tasks without violating real-time constraints.      

A fiber-optic line-switching network with a 150 Mb/s user data rate

The authors describe ImNet/2, a fiber-optic local area network, which has been specially developed for rapid image transport in picture archiving and communications systems (PACS). A comprehensive analysis of image communication requirements in hospitals led to the conclusion that current LANs would not be satisfactory under routine workload. ImNet/2 is optimized for the transmission of large datafiles. It applies line switching by means of active switch modules in a multistar topology. Once established, a link between two image equipment units continuously transfers data at a speed of 140 mB/s. Each switch unit has a total data throughput of 1.12 Gb/s. Asynchronous parallel network ports and a simple lightweight high-speed protocol make it easy to interface the network to image workstations and PACS servers. The mechanisms and components of ImNet/2 are described in detail     

Efficient radio resource management for wireless multimedia communications: a multidimensional QoS-based packet scheduler

Future wireless multimedia systems will support a variety of services with diverse range of capabilities and bit rates. For these systems, it is highly desired for real-time conversational and non-real-time services to efficiently share the available channels and bandwidth in an optimized way. The partitioned resource shaping with either fixed or a slow changing dynamic, proposed for conventional packet scheduling techniques, proves difficult and inefficient under fast-changing dynamics of radio channel and traffic. By taking into account almost all the aspects (dimensions) of quality-of-service (QoS) provisioning, the proposed unified fast dynamic multidimensional QoS-based packet scheduler (MQPS) in this paper elegantly and efficiently encapsulates features of many possible packet scheduling strategies. MQPS applies an optimization and tuning mechanism to packet scheduling weights to adopt the most appropriate packet scheduling and channel assignment strategy in response to the varying traffic and radio channel conditions. As an example, the technique is applied to a high-speed downlink packet access (HSDPA) system. It is shown that MQPS provides significantly better performance than existing techniques by satisfying all the requirements of a successful QoS provisioning to maximum possible level simultaneously.     

An Integrated Control and Scheduling Optimization Method of Networked Control Systems

Modern computer and communication network technology has made it convenient to construct networked control systems. Feedback control systems wherein the control loops are closed through a real-time network are called networked control systems (NCSs)[1]. NCSs exhibit the characteristics of high reliability, simple installation, low maintenance, good diagnostic capability, and low cost. Recently, theWhen control and feedback signals transmit through the network, the network delay emerges unavo…     

Experience with PACS in an ATM/Ethernet switched networkenvironment

Legacy local area network (LAN) technologies based on shared media concepts are not adequate for the growth of a large-scale picture archiving and communication system (PACS) in a client-server architecture. First, an asymmetric network load, due to the requests of a large number of PACS clients for only a few main servers, should be compensated by communication links to the servers with a higher bandwidth compared to the clients. Secondly, as the number of PACS nodes increases, the network throughput should not measurably cut production. These requirements can easily be fulfilled using switching technologies. Here asynchronous transfer mode (ATM) is clearly one of the hottest topics in networking because the ATM architecture provides integrated support for a variety of communication services, and it supports virtual networking. On the other hand, most of the imaging modalities are not yet ready for integration into a native ATM network. For a lot of nodes already joining an Ethernet, a cost-effective and pragmatic way to benefit from the switching concept would be a combined ATM/Ethernet switching environment. This incorporates an incremental migration strategy with the immediate benefits of high-speed, high-capacity ATM (for servers and high-sophisticated display workstations), while preserving elements of the existing network technologies. In addition, Ethernet switching instead of shared media Ethernet improves the performance considerably. The LAN emulation (LANE) specification by the ATM forum defines mechanisms that allow ATM networks to coexist with legacy systems using any data networking protocol. This paper points out the suitability of this network architecture in accordance with an appropriate system design     

Combined Connection Admission Control and Packet Transmission Scheduling for Mobile Internet Services

Mobile Internet access is expected to be the most popular communication service in the near future. In this paper, we investigate radio resource management for mobile Internet multimedia systems that use the orthogonal frequency division multiple access and adopt the adaptive modulation and coding technique. It is assumed that real-time (RT) service such as streaming video and best-effort (BE) services such as file transfer protocol and hypertext transfer protocol coexist in the systems. We suggest two levels of radio resource management schemes: the connection admission control (CAC) scheme at the first level and the packet transmission scheduler at the second level. The proposed scheduler does not assign higher priority to RT packets over BE packets unconditionally. Instead, only the RT packets that are close to the deadline are given higher priority. Therefore, the performance of BE services is improved at the cost of RT services. To control the performance degradation in RT services within an acceptable level, the CAC algorithm functions as a congestion controller. The combined effects of the proposed CAC and packet scheduling by using the cross-layer simulation that covers from the physical layer to the Internet application layer are evaluated. The numerical results show that the proposed schemes greatly improve the performance of BE services while maintaining the quality of video service at an acceptable level.     

Radio resource management for cellular CDMA systems supporting heterogeneous services

A novel radio resource management (RRM) scheme for the support of packet-switched transmission in cellular CDMA systems is proposed by jointly considering the physical, link, and network layer characteristics. The proposed resource management scheme is comprised of a combination of power distribution, rate allocation, service scheduling, and connection admission control. Power distribution allows individual connections to achieve their required signal-to-interference-plus-noise ratio, while rate allocation guarantees the required delay/jitter for real-time traffic and the minimum transmission rate requirement for non-real-time traffic. Efficient rate allocation is achieved by making use of the randomness and burstiness; of the packet generation process. At the link layer, a packet scheduling scheme is developed based on information derived from power distribution and rate allocation to achieve quality of service (QoS) guarantee. Packet scheduling efficiently utilizes the system resources in every time slot and improves the packet throughput for non-real-time traffic. At the network layer, a connection admission control (CAC) scheme based on the lower layer resource allocation information is proposed. The CAC scheme makes use of user mobility information to reduce handoff connection dropping probability (HCDP). Theoretical analysis of the grade of service performance, in terms of new connection blocking probability, HCDP, and resource utilization, is given. Numerical results show that the proposed RRM scheme can achieve both effective QoS guarantee and efficient resource utilization.