gwen Jin

QoS specification languages for distributed multimedia applications: a survey and taxonomy

Following considerable research into quality-of-service-aware application programming interface design and QoS specification language development for multimedia systems, we present a survey and taxonomy of existing QoS specification languages. As computer and communication technology evolves, distributed multimedia applications are becoming ubiquitous, and quality of service (QoS) is becoming ever more integral to those applications. Because they consume so many resources (such as memory and bandwidth), multimedia applications need resource management at different layers of the communications protocol stack to ensure end-to-end service quality, and to regulate resource contention for equitable resource sharing. However, before an application can invoke any QoS-aware resource management mechanisms and policies - such as admission control, resource reservation, enforcement, and adaptation - it must specify its QoS requirements and the corresponding resource allocations. Furthermore, the application must describe how QoS should be scaled and adapted in cases of resource contention or resource scarcity during runtime. Our goal in this article is to systematically classify and compare the existing QoS specification languages that span several QoS layers with diverse properties. The provided taxonomy and the extensive analysis will give us a detailed look at the existing QoS specification languages along with their properties and relations.

Source-based QoS service routing in distributed service networks

Based on the distributed and composable services model, the QoS service routing/composition problem has emerged as the middleware support for multimedia applications. Different from the conventional QoS data routing, QoS service routing presents additional challenges caused by the service functionality, service dependency, resource requirement heterogeneity, and loop issues that make solutions for QoS data-routing inapplicable to QoS service routing. Existing solutions for addressing this problem are either not generic enough or not integrated, so that they either become inapplicable to new environments/metrics or the computed paths are sub-optimal. This paper presents a generic and integrated approach for computing optimal service paths, and shows an aggregate performance function - F- that optimizes several QoS metrics at the same time. Simulations show that F is superior, and integrating service configuration selection with service path finding is desirable.

QoS-Aware service management for component-based distributed applications

Component-based software development has evolved from a tightly coupled style to a loosely coupled style in the recent few years. The paradigm shift will eventually allow heterogeneous systems to interoperate in open networks such as the Internet and will make software development more of a management task than a development task. Envisioning that future applications may comprise dynamically aggregated component services possibly distributed widely, we develop a Quality of Service (QoS)-aware service management framework in the middleware layer to make the component services infrastructure transparent to the applications. Specifically, we manage services not only as individuals, but more importantly as meaningful aggregated entities based on the logical compositional needs coming from the applications, by composing services properly according to QoS requirements at application setup time, and performing continuous maintenance at application runtime seamlessly. Our service management framework is scalable in two dimensions: network size and applications client population size. Specifically, the framework employs a decentralized management solution that scales to large network size, and explores resource sharing in one-to-many group-based applications by means of multicasting mechanisms. Moreover, it incorporates local adaptation operations and distributed failure detection, reporting, and recovery mechanisms to deal with runtime resource fluctuations and failures.

On construction of service multicast trees

Internet heterogeneity has been a major problem in multimedia data delivery. To deal with the problem, overlay proxy networks as well as distributed and composable services across these overlay networks are being deployed. This solution however, implies that the overlay networks must support not only data multicast for data delivery to a group of destinations, but also service multicast (incorporate services in the distribution tree) for semantic data transformations in order to deal with Internet heterogeneity. This paper presents challenges and solutions fro building service multicast trees. We compare two groups of algorithms, the shortest-service-path tree (SSPT) algorithm and the longest-match (LM) algorithm. Simulation results show trade-offs between complexity and overall tree performance, as well as cost differences when further refinements of the LM approach are considered.

Resource- and quality-aware application-level service multicast

Current multimedia application deployment tends to rely on composable service systems, where a complex multimedia service can be composed dynamically from multiple simpler ones distributed widely in the Internet. Related to such a scenario is the problem of finding efficient service paths that meet end-to-end requirements. Work has been done in discovering unicast service paths. However, considering that resources are limited, for distributed multimedia applications that may have a single sender but multiple heterogeneous end-users, it is demanding to build service trees to minimize resource usages by means of sharing. We present a resource- and quality-aware application-level multicast Service Path Finding protocol (mc-SPF/sup Q/) that constructs, for each application, a more economical service tree instead of independent service paths. Bandwidth and proxy machine resource savings can be achieved by applying the application-layer multicast concept to deliver data through the service tree. mc-SPF/sup Q/ Is resource- and quality-aware, in that service paths are discovered with resource availability and clients quality demand in mind. Our simulation results show that: (1) compared to unicast service path finding solutions, mc-SPF/sup Q/ is superior; (2) the proxy load balancing feature makes the protocol achieve better path finding success rates in the face of resource scarcity; (3) reserving different portions of resources for service requests of different qualities affects the service path finding success rate and the average quality of service.

Large-scale service overlay networking with distance-based clustering

The problem of service routing (or dynamic service composition) has recently emerged as a consequence of the distributed composable services model residing in middleware layer(s). However, existing solutions are mostly suitable for small- or medium-scale service overlay networks, as service routing is performed over flat overlay topologies such as a mesh. Due to their increasing routing information maintenance costs, these flat (single-level) topology solutions cannot cope with large-scale service overlay networking. For better scalability, in this paper, we provide a hierarchical service routing framework, which comprises three parts. In the first part, we organize the overlay network nodes into clusters based on their Internet distances. We then construct a hierarchically fully connected (HFC) topology based on the clustering result. In such a topology, nodes within a cluster are considered fully connected, and the clusters themselves are also fully connected by their border nodes. In the second part, a hierarchical state information distribution protocol will be provided so that each node in the system maintains full state of the nodes in its own cluster and aggregate state of other clusters in the system. In the third part, we present how service paths can be computed hierarchically in a divide-and-conquer fashion. Through simulation tests, we demonstrate that while achieving much better scalability, our framework provides also as good and efficient service paths as single-level mesh solutions.

QoS service routing in one-to-one and one-to-many scenarios in next-generation service-oriented networks

The QoS service routing problem has recently emerged as a consequence of the increasingly accepted distributed and composable services model. Different from the conventional QoS data routing, QoS service routing presents additional challenges caused by the service functionality, service dependency, resource requirement heterogeneity, and loop formation issues, that make solutions for QoS data routing inapplicable to QoS service routing. We study this problem both in one-to-one and one-to-many application scenarios, so that despite the fact that the component services are located distributively in multiple hosts, the system can still provide integrated services seamlessly and efficiently.

Large-Scale QoS-Aware Service-Oriented Networking with a Clustering-Based Approach

Motivated by the fact that most of the existing QoS service composition solutions have limited scalability, we develop a hierarchical-based solution framework to achieve scalability by means of topology abstraction and routing state aggregation. The paper presents and solves several unique challenges associated with the hierarchical-based QoS service composition solution in overlay networks, including topology formation (cluster detection and dynamic reclustering), QoS and service state aggregation and distribution, and QoS service path computation in a hierarchically structured network topology. In our framework, we (1) cluster network nodes based on their Internet distances and maintain clustering optimality at low cost by means of local reclustering operations when dealing with dynamic membership; (2) use data clustering and Bloom filter techniques to jointly reduce complexity of data representation associated with services within a cluster; and (3) investigate a top-down approach for computing QoS service paths in a hierarchical topology.

A Distributed Approach for QoS Service Multicast with

The service routing problem emerged from the distributed and composable services model. Using service multicast instead of service unicast for group delivery saves bandwidth and resources. The authors describe a distributed approach for building QoS-assured, delay-efficient service multicast trees that uses geometric location information and explore hybrid multicasting (service multicasting plus data multicasting).