We propose a scheme called Type-Aware Error Control (TAEC) to provide robust interactive video services over time-varying wireless channels. Basically, TAEC explores the temporal dependence of video frames by pushing out the lower impact frames. In doing so, queuing delay is controlled and the important frame is retransmitted multiple times. We consider the application of the nonstationary stochastic control to further improve the wireless system throughput by exploring the multiuser diversity gain. The techniques involved in our proposed solution consist of constructing a Markov model, reducing the number of parameters estimated, and avoiding the state explosion problem. The provisioning of immediate bandwidth guarantee is another feature of TAEC, i.e., when exploring the multiuser diversity gain, the users share their reserved bandwidth only if the perceived video qualities are acceptable. As shown in the simulation, TAEC improves the perceived video quality in terms of luminance PSNR when compared to other schemes.

We propose a practical Ethernet access architecture to support high availability and service continuity for IPTV. To reduce the per-line cost, our approach is interconnecting switches, most of which are low-cost, in a hierarchical fashion to provide broadband and cost-effective IPTV multicasting. The remaining key issue is to endow the IPTV services with high availability. To this end, we base on the redundant pair method and propose an architecture which achieves short failover process to seamlessly continue the IPTV services. In realization, our effort is restricted in extending the IGMP proxy running on the switch controller, and we describe our realization by presenting the basic design principle. To demonstrate its viability, we test our proposed architecture on ACTA which is a commercially available platform. Experiment results show that in general the failover process can be carried out within 50 ms.

Proxy partial caching, e.g. segment-based proxy caching or proxy prefix caching, partitions the object into nonoverlapping pieces. The proxy cache then treats each piece as an individual file when performing caching and replacing. Upon receipt of request to the object, the proxy cache delivers the cached portion to the client immediately to mask the start-up delay. However, two architectural challenges are confronted when implementing this technique in the web proxy software, e.g., Squid cache. The first challenge is related to caching video streams. Although not until recently, HTTP is recognized as an efficient method to support interactive video. Many fundamental issues are still required to be solved. To this end, we propose an approach of segment-based video streams retrieval and caching via HTTP byte-range requests to further mask the possible startup delay, enhance the interactive function "pause", and simplify the web proxy cache design. Proxy partial caching introduces the second architectural challenge called dirty-initial-segments problem, i.e. cached portion in the proxy cache is inconsistent with the original in the server. If this happens, the cached portion already delivered to the client cannot be concatenated with the latter portion from the server. To relieve this problem, we propose a novel algorithm called validating upon partial replacement, which synchronizes the operations of proactive consistency validation, partition and replacement performed upon an object. We show that our proposed algorithm bears the merit of controllable chance to disturb users, easily embedding into the existing web proxy cache software with minimum modification, and improving the cache performance.

Proxy prefetch caching aims to reduce the latency in serving web requests by prefetching objects into the proxy cache in anticipation that they might be requested. Thus, when the clients actually request them, these objects can be served directly from the proxy cache without having to be fetched all the way from the remote server. A key component in proxy prefetch caching is the mechanism to determine the profitability of prefetching. A good prefetch advisor must consider not only factors such as the request probability of the prefetched objects, the network bandwidth, and object size, but also the cache space and those objects already in the cache. A unified framework is therefore needed, under which the prefetch advisor can judge whether prefetching some objects by replacing some other objects in the cache can lead to a reduction in the average user access time. In this paper we introduce a framework that unifies prefetch caching and cache replacement with a single index called object profit. The proposed framework is very general that it can be applied to almost any type of web objects, and it considers network bandwidth, cache capacity and replacement, object size, and analysis simplicity together. We will derive the object profit mathematically and then discuss how to apply the framework in practice. The proposed scheme is evaluated with simulation. As the simulation shows, the latency reduction by using the proposed framework can be maximized.

Dispersity multicasting is an extension of dispersity routing for multicast communication. In dispersity multicasting, m arc-disjoint subtrees are used for source-destination message delivery. If the bottleneck flow control is applied to each of the m arc-disjoint subtrees, there might still exist extra bandwidth for the multicast communication. To exploit the extra bandwidth, we introduce the concept of virtual connections. We design a flow control algorithm for the available-bit-rate dispersity multicasting with two arc-disjoint subtrees and one virtual connection. Issues in applying the algorithm to ATM networks are discussed. Simulation studies show that, in general, our algorithm enhances the throughput of dispersity multicasting.

Adaptive nonminimal routing (or misrouting) may move messages away from their destinations to temporarily cope with the dynamic load in an interconnection network. In most cases, misrouting is more powerful and flexible than minimal routing, especially under nonuniform load distribution. However, to take advantage of its misrouting, we have to avoid deadlock, livelock, and starvation in the network and to maintain the network performance across all levels of loading. In this paper, we propose a new flow control scheme for misrouting, called valved routing. Valved routing controls message injection and transmission through logical valves associated with the router ports. Designing routers using valved routing requires a proper choice of design parameters. We will discuss how to find the range of feasible design parameters. Issues in implementing routers using valved routing will also be addressed. We have conducted extensive simulations to compare the performance of routers with and without valved routing. Our simulation results show that valved routing has promising performance advantages, at light as well as heavy network load. Compared with the voluntary misrouting, valved routing performs better in network throughput without sacrificing the latency.>