Protocol architecture for multimedia applications over ATM networks

At the data-link layer, ATM offers a number of features, such as high-bandwidth and per-session quality-of-service (QoS) guarantees, making it particularly attractive to multimedia applications. Unfortunately, many of these features are not visible to applications because of the inadequacies of existing higher-level protocol architectures. Although there is considerable effort underway to tune these protocols for ATM networks, we believe that a new ATM-specific protocol stack is essential to effectively exploit all the benefits of ATM. We describe the semantics of such a protocol stack, and discuss its advantages over traditional protocol architectures from the perspective of multimedia applications. The performance impact of the new protocol architecture is experimentally demonstrated on a video conferencing testbed built around IBM RS/6000's equipped with prototype hardware for video/audio processing, and connected via ATM links     

Strategies for dynamic load balancing on highly parallel computers

Dynamic load balancing strategies for minimizing the execution time of single applications running in parallel on multicomputer systems are discussed. Dynamic load balancing (DLB) is essential for the efficient use of highly parallel systems when solving non-uniform problems with unpredictable load estimates. With the evolution of more highly parallel systems, centralized DLB approaches which make use of a high degree of knowledge become less feasible due to the load balancing communication overhead. Five DLB strategies are presented which illustrate the tradeoff between 1) knowledge - the accuracy of each balancing decision, and 2) overhead - the amount of added processing and communication incurred by the balancing process. All five strategies have been implemented on an Inter iPSC/2 hypercube     

End to end QoS provisioning multimedia wireless/mobile networksusing an adaptive framework

This article presents a framework for multimedia networking in a wireless and mobile environment. We consider both multimedia application needs as well as networking requirements, and try to bridge these paradigms using an adaptive framework. Central to this framework is the concept of representing a multimedia connection in terms of multiple substreams each with their own specified QoS requirement and making network elements (switching and access points), services, and protocols (signaling, control, routing) aware of the QoS requirements of such substreams. As resource availability in the wireless and mobile network fluctuates, the network selects and schedules substreams in order to present the information content with an acceptable quality at a receiver (or each receiver in case of multicast connections). This is done while achieving a reasonable utilization efficiency of network resources and sharing them in a fair manner     

The sink tree paradigm: connectionless traffic support on ATM LAN's

Asynchronous transfer mode (ATM) is a connection-oriented technology in which all communication is based on virtual connections established prior to the transfer of data. It is expected that the bulk of traffic carried by the ATM network will be data traffic, e.g., local area network (LAN) internetwork traffic. Hence, a major issue regarding ATM is the support for connectionless (datagram) traffic. A scheme for the efficient support for connectionless traffic in ATM LANs based on trees of virtual connections is proposed. In this scheme, a sink tree is built for every switch in the LAN. Each tree provides an efficient means of routing connectionless traffic from any switch in the network to the sink switch (root) of the tree. The sink tree solution may also be used to broadcast connectionless messages in the reverse direction. The trees can easily be updated to adapt to topological changes or congestion in the network. A protocol for refreshing the tree structure using the ATM switch routing tables is described. An adaptive rate control solution, in conjunction with fast back pressure at the ATM layer, is presented. It is shown that this scheme achieves high utilization of available bandwidth for connectionless traffic, has low cell loss probability, and small overhead     

Videoconferencing over packet-based networks

The Internet explosion is driving the need for new collaboration tools which will enable two or more users to share data, audio, and video. The real-time packet-based solutions which are emerging differ considerably from the circuit-switch solutions which have existed for some time now. In this paper, we present one such packet-based approach, the Multimedia Multiparty Teleconferencing (MMT) system, which was fully implemented as a research prototype. Using MMT as an example, we address some of the fundamental issues related to videoconferencing systems in a packet-based environment, and discuss the differences with the traditional circuit-switch approaches, namely, the ITU H.320 standard. In particular, MMT is a distributed solution, while H.320 is centralized. The use of multicast and a novel video-mixing technique to facilitate the distributed solution are presented. Furthermore, MMT audio and video streams are susceptible to congestion and packet loss in the shared media packet-based environment, while H.320 streams use dedicated connections. As such, synchronization, error resilience, and dynamic rate control schemes for the packet-based system are presented     

The use of priorities on token-ring networks for multimedia traffic

The authors consider the transport of multimedia traffic on a token-ring LAN. In order to guarantee acceptable QoS for multimedia traffic, resource management is required to insure that sufficient capacity from all shared resources is allocated to the priority traffic. Once a multimedia session is accepted and resources have been allocated, the next task is to insure that the high priority multimedia traffic actually obtains the resources which have been allocated to it     

Approximating dependability measures of computer networks: an FDDIcase study

An approximation technique is presented to evaluate the dependability of FDDI networks. This technique, based on the most likely paths to failure concept, is simple and practical. It may be applied easily to evaluate and compare the dependability of different FDDI network configurations. The effects of various network parameters on the network availability are examined. We conclude that, in order to guarantee high availability, an FDDI network backbone should be interconnected using dual-attachment concentrators. Furthermore, dual-homing configurations are required for high-availability paths between end stations and the backbone. For less stringent availability requirements, single-attachment concentrator trees with single attachment stations may suffice. We also discuss how the technique may be extended easily to more general heterogeneous networks including Token Ring and Ethernet