Dynamicmultimedia protocol stacks

Fixed end-system protocols are unable to support the wide range of applications requirements on top of current networks without adding overhead in the form of unnecessary functionality for multiple combinations of application requirements and networks.This paper presents the Real-time Wide Area Network Dissemination Architecture Protocol (RWANDA), which dynamically configures multimedia protocol stacks to support a wide range of application requirements and to increase performance. It overcomes synchronous limitations by providing an asynchronous group communication model. Applications only pay for required quality of service (QoS) such as multicast, virtual synchrony and encrypted communication.In RWANDA, information sources use channels to disseminate information to a potentially large and changing set of channel subscribers. RWANDA recognises the differing media characteristics and transport requirements of multimedia by providing a protocol composition framework that extends to incorporate yet unsupported communication protocols, qualities of service and optimised multimedia stacks. RWANDA provides an asynchronous foundation necessary for developing a large-scale wide area network continuous media protocol.     

Virtual network transport protocols for Myrinet

Bringing direct and protected network multiprogramming into mainstream cluster computing requires innovations in three key areas: application programming interfaces, network virtualization systems, and lightweight communication protocols for high-speed interconnects. The AM-II API extends traditional active messages with support for client-server computing and facilitates the construction of parallel clients and distributed servers. Our virtual network segment driver enables a large number of arbitrary sequential and parallel applications to access network interface resources directly in a concurrent but fully protected manner. The NIC-to-NIC communication protocols provide reliable and at-most-once message delivery between communication endpoints. The NIC-to-NIC protocols perform well as the number of endpoints and the number of hosts in the cluster are scaled. The flexibility afforded by the underlying protocols enables a diverse set of timely research efforts. Other Berkeley researchers are actively using this system to investigate implicit techniques for the coscheduling of communicating processes, an essential part of high-performance communications in multiprogrammed clusters of uni- and multiprocessor servers. Other researchers are extending the active message protocols described here for clusters of symmetric multiprocessors, using so-called multiprotocol techniques and multiple network interfaces per machine     

Challenges and Lessons in Developing Middleware on Smart Phones

Several research projects pursuing middleware architectures to support pervasive applications on smart phones reveal the importance of careful resource management, lightweight communication protocols, and asynchronous programming.     

The performance impact of traffic patterns on routing protocols in mobile ad hoc networks

As mobile ad hoc network (MANET) systems research has matured and several testbeds have been built to study MANETs, research has focused on developing new MANET applications such as collaborative games, collaborative computing, messaging systems, distributed security schemes, MANET middleware, peer-to-peer file sharing systems, voting systems, resource management and discovery, vehicular computing and collaborative education systems. The growing set of diverse applications developed for MANETs pose far more complex traffic patterns than the simple one-to-one traffic pattern, and hence the one-to-one traffic pattern widely used in previous protocol studies has become inadequate in reflecting the relative performance of these protocols when deployed to support these emerging applications.As a first step towards effectively supporting newly developed and future diverse MANET applications, this paper studies the performance impact of diverse traffic patterns on routing protocols in MANETs. Specifically, we propose a new communication model that extends the previous communication model to include a more general traffic pattern that varies the number of connections per source node. We study the performance impact of traffic patterns on various routing protocols via detailed simulations of an ad hoc network of 112 mobile nodes. Our simulation results show that many of the conclusions drawn in previous protocol comparison studies no longer hold under the new traffic patterns. These results motivate the need for performance evaluation of ad hoc networks to not only include rich and diverse mobility models as has been done in the past but also include diverse traffic patterns that stress a wide set of protocol design issues.     

通信协议的并行机制研究

通信技术的迅速发展，通信网络所提供的带宽达到几百Ｍｂｐｓ～Ｇｂｐｓ数量级。一些应用，象多媒体通信，就能利用网络的高吞吐量。但是，目前的通信协议并不能适应高速传输的环境。运输层和其它较高层协议的处理，已成为通信系统的性能瓶颈。本文首先回顾近十年来通信环境所发生的一些变化，并分析其对运输层协议的影响；第二部分分析标准协议并行实现时的一些关键技术；最后介绍了一个运输层系统模型，该模型采用并行机制，向上提供高性能的运输层服务。     

Intelligent multicast routing for multimedia over cognitive radio networks: a probabilistic approach

Cognitive radio (CR) technology has been demonstrated as one of the key technologies that can provide the needed spectrum bands for supporting the emerging spectrum-hungry multimedia applications and services in next-generation wireless networks. Multicast routing technique plays a significant role in most of wireless networks that require multimedia data dissemination to a group of destinations through single-hop or multi-hop communication. Performing multimedia multicasting over CR networks can significantly improve the quality of multimedia transmissions by effectively exploiting the available spectrum, reducing network traffic and minimizing communication cost. An important challenge in this domain is how to perform a multi-cast transmissions over multiple hops in a dynamically varying CR environment while maintaining high-quality received video streaming to all multi-case CR receivers without affecting the performance of legacy primary radio networks (PRNs). In this paper, we investigate the problem of multicast multimedia streaming in multi-hop CR networks (CRNs). Specifically, we propose an intelligent multicast routing protocol for multi-hop ad hoc CRNs that can effectively support multimedia streaming. The proposed protocol consists of path selection and channel assignment phases for the different multi-cast receivers. It is based on the shortest path tree (SPT) that implements the expected transmission count metric (ETX). The channel selection is based on the ETX, which is a function of the probability of success (POS) over the different channels that depends on the channel-quality and availability. Simulation results verify the significant improvement achieved by the proposed protocol compared to other existing multicast routing protocols under different network conditions.

     

Modeling and performance evaluation of transport protocols for firewall control

Firewalls are a crucial building block for securing IP networks. The usage of out-of-band signaling protocols such as SIP for IP telephony and multimedia applications requires a dynamic control of these firewalls and imposes several challenges. Recently, several firewall control architectures and protocols have been developed. The main focus of this paper is the simple middlebox configuration protocol (SIMCO), which is a new transaction-based firewall control protocol. Due to the impact on call setup delays, firewall signaling requires small end-to-end delays and thus mandates a careful choice of the transport protocol. Therefore, this paper studies SCTP, TCP and UDP-based transport for SIMCO and compares different configurations that allow to optimize the performance. We present an analytical model to quantify the impact of head-of-line blocking in SCTP and TCP and verify it with measurements. Both the model and measurements reveal that SCTP can significantly reduce the SIMCO response times by leveraging transmission over multiple parallel streams. While already a few SCTP streams can almost completely avoid head-of-line blocking, our results show that TCP- and UDP-based transport may suffer from significantly larger delays.     

Low‐latency Java communication devices on RDMA‐enabled networks

Providing high‐performance inter‐node communication is a key capability for running high performance computing applications efficiently on parallel architectures. In fact, current systems deployments are aggregating a significant number of cores interconnected via advanced networking hardware with Remote Direct Memory Access (RDMA) mechanisms, that enable zero‐copy and kernel‐bypass features. The use of Java for parallel programming is becoming more promising thanks to some useful characteristics of this language, particularly its built‐in multithreading support, portability, easy‐to‐learn properties, and high productivity, along with the continuous increase in the performance of the Java virtual machine. However, current parallel Java applications generally suffer from inefficient communication middleware, mainly based on protocols with high communication overhead that do not take full advantage of RDMA‐enabled networks. This paper presents efficient low‐level Java communication devices that overcome these constraints by fully exploiting the underlying RDMA hardware, providing low‐latency and high‐bandwidth communications for parallel Java applications. The performance evaluation conducted on representative RDMA networks and parallel systems has shown significant point‐to‐point performance increases compared with previous Java communication middleware, allowing to obtain up to 40% improvement in application‐level performance on 4096 cores of a Cray XE6 supercomputer. Copyright © 2015 John Wiley & Sons, Ltd.     

An interface to a reliable packet delivery service for parallelsystems

Modern distributed memory parallel computers provide hardware support for the efficient and reliable delivery of interprocessor messages. This facility needs to be accessed by lightweight protocols that do not waste the performance of the underlying hardware; the heavyweight layering techniques traditionally used in distributed systems are wholly inappropriate. A low-level communication interface is therefore presented which exploits modern architectures effectively, while maintaining a good match to existing parallel programming environments. The interface defines mechanisms to access an asynchronous reliable packet delivery service. It permits messaging protocols to be efficiently synthesized by considering the activity at their end-points alone. This arrangement effectively decouples the implementation of protocols from low-level architectural features, and hence aids the portability of parallel programming environments. Furthermore, the interface allows the communication network to be shared by multiple programming paradigms, giving additional flexibility over existing systems     

MRTP: a multiflow real-time transport protocol for ad hoc networks

Real-time multimedia transport has stringent quality of service requirements, which are generally not supported by current network architectures. In emerging mobile ad hoc networks, frequent topology changes and link failures cause severe packet losses, which degrade the quality of received media. However, in such mesh networks, there usually exist multiple paths between any source and destination nodes. Such path diversity has been demonstrated to be effective in combating congestion and link failures for improved media quality. In this paper, we present a new protocol to facilitate multipath transport of real-time multimedia data. The proposed protocol, the multiflow real-time transport protocol (MRTP), provides a convenient vehicle for real-time applications to partition and transmit data using multiple flows. We demonstrate through analysis that data partitioning, which is an essential function of MRTP, can effectively reduce the short-range dependence of multimedia data, thus improving its queueing performance in underlying networks. Furthermore, we show that a few flows are sufficient for MRTP to exploit most of the benefits of multipath transport. Finally, we present a comprehensive simulation study on the performance of MRTP under a mobile ad hoc network. We show that with one additional path, MRTP outperformed single-flow RTP by a significant margin.     

Communication support for distributed collaborative applications

The development of distributed, multimedia, collaborative applications requires the resolution of communication issues such as concurrency control and temporal and causal synchronization of traffic over related data streams. Existing transport and/or session-layer protocols do not include the desired support for multistream, multipoint communication. In this paper, we propose new communication abstractions and mechanisms that facilitate the implementation of the necessary coordination and concurrency control semantics in a collaborative application. We propose a protocol suite called themultiflow conversation protocol (MCP) for the realization of these abstractions and describe its prototype implementation in an internetwork of workstations. The paper also describes our experience with the prototype and results of a performance evaluation.     

Biswapped networks: a family of interconnection architectures with advantages over swapped or OTIS networks

We propose a new family of communication architectures called ‘biswapped networks’. Given any n-node basis network Ω, the associated biswapped network Bsw(Ω) is built of 2n copies of Ω, using a simple rule for connectivity that ensures desirable attributes, including regularity, modularity, fault tolerance, and algorithmic efficiency. In particular, if Ω is a Cayley digraph, then so is Bsw(Ω). Our biswapped connectivity provides a systematic scheme for synthesizing large, scalable, modular, and robust parallel architectures. Furthermore, many desirable attributes of the underlying basis network Ω are preserved, as the Bsw(Ω) parameters are related to the corresponding parameters of Ω. We obtain a number of results on internode distances, Hamiltonian cycles, optimal routing, and node-disjoint paths for Bsw(Ω). We explore the relations between biswapped and swapped or optical transpose interconnection system (OTIS) networks, which may use a mix of electronic and optical links. In particular, we demonstrate that the biswapped connectivity removes an inherent asymmetry of swapped/OTIS networks, as well as the attendant complications in analyses and applications. Finally, we show that biswapped networks are complementary to, and offer advantages over, well-known and widely used interconnection architectures for parallel processing.     

Middleware infrastructure for parallel and distributed programming models in heterogeneous systems

We introduce a middleware infrastructure that provides software services for developing and deploying high-performance parallel programming models and distributed applications on clusters and networked heterogeneous systems. This middleware infrastructure utilizes distributed agents residing on the participating machines and communicating with one another to perform the required functions. An intensive study of the parallel programming models in Java has helped identify the common requirements for a runtime support environment, which we used to define the middleware functionality. A Java-based prototype, based on this architecture, has been developed along with a Java object-passing interface (JOPI) class library. Since this system is written completely in Java, it is portable and allows executing programs in parallel across multiple heterogeneous platforms. With the middleware infrastructure, users need not deal with the mechanisms of deploying and loading user classes on the heterogeneous system. Moreover, details of scheduling, controlling, monitoring, and executing user jobs are hidden, while the management of system resources is made transparent to the user. Such uniform services are essential for facilitating the development and deployment of scalable high-performance Java applications on clusters and heterogeneous systems. An initial deployment of a parallel Java programming model over a heterogeneous, distributed system shows good performance results. In addition, a framework for the agents' startup mechanism and organization is introduced to provide scalable deployment and communication among the agents.     

A multi-access technique for broadband wireless local networks

This paper presents a new multi-access technique that allows multimedia information to be transported in indoor wireless networks. Growing emphasis on multimedia calls for the development of multi-access protocols capable of supporting demanding applications such as audio/video playback, image browsing, real-time voice/video transmission and interactive data exchange in a unified manner. To this end, a practical multi-access scheme called `reserved polling' is proposed. The technique handles a diverse mixture of delay classes and message priorities associated with multimedia traffic with an inherent ability to adapt to the traffic load profile. In order to gain a quantitative insight into its behavior, the protocol is analyzed and simulated in detail.     

A protocol for deadlock-free dynamic reconfiguration in high-speedlocal area networks

High-speed local area networks (LANs) consist of a set of switches interconnected by point-to-point links, and hosts linked to those switches through a network interface card. High-speed LANs may change their topology due to switches being turned on/off, hot expansion, link remapping, and component failures. In these cases, a distributed reconfiguration protocol analyzes the topology, computes the new routing tables, and downloads them to the corresponding switches. Unfortunately, in most cases, user traffic is stopped during the reconfiguration process to avoid deadlock. These strategies are called static reconfiguration techniques. Although network reconfigurations are not frequent, static reconfiguration such as this may take hundreds of milliseconds to execute, thus degrading system availability significantly. Several distributed real-time applications have strict communication requirements; Distributed multimedia applications have similar, although less strict, quality of service (QoS) requirements. Both stopping packet transmission and discarding packets due to the reconfiguration process prevent the system from satisfying the above requirements. Therefore, in order to support hard real-time and distributed multimedia applications over a high-speed LAN, we need to avoid stopping user traffic and discarding packets when the topology changes. In this paper, we propose a new deadlock-free distributed reconfiguration protocol that is able to asynchronously update routing tables without stopping user traffic. This protocol is valid for any topology, including regular as well as irregular topologies. It is also valid for packet switching as well as for cut-through switching techniques and does not rely on the existence of virtual channels to work. Simulation results show that the behavior of our protocol is significantly better than for other protocols based on stopping user traffic     

支持多媒体通信的网络协议技术及其发展

随着多媒体应用的普及，人们对多媒体在网络上的传输提出了新的要求，本文首先分析了现有网络协议支持多媒体通信存在的问题，然后讨论了网络传输协议IPv6、RSVP和实时传输协议RTP对多媒体的支持，展望了网络通信的发展和实现等技术。     

Parallel transport subsystem implementation for high-performance communication

Requirements of emerging applications together with rapid changes in networking technology towards gigabit speeds require new adequate transport systems. Integrated designs of transport services, protocol architecture and implementation platforms are required by forthcoming applications in high-speed network environments. The transport subsystem PATROCLOS (parallel transport subsystem for cel/ based high-speed networks) is designed with special emphasis on a high degree of inherent parallelism to allow efficient implementations on multiprocessor architectures combined with specialized hardware for very time critical functions. The paper presents the new parallel protocol architecture of PATROCLOS, an appropriate implementation architecture based on transputer networks, and performance evaluation results, which indicate high throughput values.     

Grid-distributed visualizations using connectionless protocols

The NERSC and Lawrence Berkeley National Laboratory visualization group has developed the Visapult tool to attack grand challenge problems. Visapult is a distributed, parallel, volume rendering application that leverages parallel computation and high-performance networking resources that are on the same scale as the supercomputers generating the data. We've improved Visapult's effectiveness using aggressive network tuning and network protocol modifications. In particular, we used a new connectionless user datagram protocol (UDP) to improve network efficiency from a 25 to 88 percent line rate increase for multigigabit networks. This connectionless protocol also dramatically reduces the latency of network event delivery, improving the responsiveness of wide area distributed interactive graphics applications as compared to transmission control protocol (TCP) streams. We believe that this UDP protocol, as well as transport encodings and algorithms that can tolerate loss gracefully, will become a fundamental component of future grid visualization architectures.     

ATM局域网与局域网互联技术

由于日益增长多媒体技术的应用和对一般数据的高速传输业务的需求，ＡＴＭ技术应运而生。将ＡＴＭ引入局域网成败关键在于它是否能提供与现行协议和应用程序兼容的类似的局域网业务。为此，本文主要讨论ＡＴＭ引入局域网时，实现局网无连接服务，协议适配以及与ＡＴＭ广域网互联过程。