We are building a very high performance 1.2 Gb/s ATM network interface chip called the APIC (ATM Port Interconnect Controller). In addition to borrowing useful ideas from a number of research and commercial prototypes, the APIC design embraces several innovative features, and integrates all of these pieces into a coherent whole. This paper describes some of the novel ideas that have been incorporated in the APIC design with a view to improving the bandwidth and latency seen by end-applications. Among the techniques described, Protected DMA and Protected I/O were designed to allow applications to queue data for transmission or reception directly from user-space, effectively bypassing the kernel. This argues for moving the entire protocol stack including the interface device driver into user-space, thereby yielding better latency and throughput performance than kernel-resident implementations. Pool DMA when used with Packet Splitting, is a technique that can be used to build true zero-co...

The problem this research addresses is how to modify an existing operating system's I/O subsystem to support new high-speed networks and high-bandwidth multimedia applications that will play an important role in future computing environments.

Collaboration in networked multimedia applications requires means to coordinate the activities of a dynamically aggregating set of distributed users, working with various multimedia data on heterogeneous platforms. A floor denotes a control right over a shared resource within a collaborative workspace. Floor control, similar to concurrency control for databases, is gradually being integrated into shared applications to orchestrate the access and dynamic process of joint work on shared data, supporting or substituting a human conference chair. This paper presents a comprehensive view on floor control, analyzing requirements for protocols with respect to the variety of shared tools, describing an architecture to meet these requirements, and finally placing our work in the context of previous efforts. Keywords -- Floor control, collaborative multimedia computing, Computer-Supported Cooperative Work (CSCW). 1. Introduction For multimedia applications, a gradual shift from standalone to...

Quality assurance of multimedia applications and services by means of testing will be a great challenge for manufacturers and service providers. Standardized methods and tools for conformance testing are only applicable to traditional protocols (one single data stream, no timing requirements). In this paper we discuss a testing methodology and framework for testing multimedia services. We have started developing and implementing a test specification language called TeleCommunication Test Specification and implementation Language (TelCom TSL). TelCom TSL is meant to be a tool for specifying and implementing test cases for (distributed) multimedia services. TelCom TSL defines a novel testing architecture and has a formal syntax and semantics. With its real-time extensions, TelCom TSL is particularly applicable for testing multimedia services. The contributions of this paper are an analysis of different quality-of-service (QoS) semantics in the context of multimedia applications, a defini...

One of the ways in which the APIC addresses the memory bottleneck alluded to above is to function in a desk-area environment where different memories can be used to spread the load. The idea here is to dedicate one APIC chip and one memory bank to each high-bandwidth device in the system, thereby shedding the load from a host system's main memory. Several such APIC-memory device combinations can be daisy chained to form a desk-area network with high bandwidth and low latency characteristics.

Real-time upcalls (RTUs) are an operating systems mechanism that can be used by applications to efficiently schedule code segments (or handlers) that must execute periodically. While the mechanism was conceived to support protocol processing with quality-of-service guarantees for networked multimedia applications it is general enough to be applicable in other domains like real-time image processing. Until now real-time threads have been the only mechanism for implementing protocols in user space with QoS guarantees. The RTU mechanism avoids the implementation complexity of the thread based approach while retaining its ability to ensure real-time behavior. In addition, our design simplifies protocol code, improves performance, and can be ported to most systems. A key feature of RTU scheduling is the pre-emption scheme that exploits the iterative nature of protocol processing by allowing an RTU to yield the CPU by returning from the invocation. This obviates the need for RTU handlers to...

Over recent years, middleware is becoming an increasingly important tool for distributed application development. Furthermore, coupled with object-oriented development techniques, middleware is becoming the de facto approach to distributed application programming. Already, standardised distributed object platforms have emerged, including the Object Management Group’s CORBA and Microsoft’s DCOM. In their maturity, the services that such platforms offer are becoming progressively richer, as new horizontal application requirements are addressed. Examples of these ‘value added’ services include support for transactions, asynchronous messaging, persistence, migration and concurrency. These are now all considered basic services and are consequently integrated in the off-the-shelf middleware packages. Nevertheless, one of the most significant challenges in addressing horizontal requirements is that of support for continuous media, and as a superset, multimedia applications. Continuous media requires new interaction paradigms and consequently new modelling abstractions beyond conventional client/server communications.