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Abstract. To be an effective platform for performance-sensitive realtime and embedded applications, off-the-shelf CORBA middleware must preserve the communication-layer quality of service (QoS) properties of applications end-to-end. However, the standard CORBA GIOP/IIOP interoperability protocols are not well suited for applications that cannot tolerate the message footprint size, latency, and jitter associated with general-purpose messaging and transport protocols. It is essential, therefore, to develop standard pluggable protocols frameworks that allow custom messaging and transport protocols to be configured flexibly and used transparently by applications. This paper provides three contributions to research on pluggable protocols frameworks for performance-sensitive distributed object computing (DOC) middleware. First, we outline the key design challenges faced by pluggable protocols developers. Second, we describe how we resolved these challenges by developing a pluggable protocols framework for TAO, which is our high-performance, real-time CORBA-compliant ORB. Third, we present the results of benchmarks that pinpoint the impact of TAO's pluggable protocols framework on its end-to-end efficiency and predictability. Our results demonstrate how the application of optimizations and patterns to DOC middleware can yield both highly flexible/reusable designs and highly efficient/predictable implementations. In particular, the overall roundtrip latency of a TAO two-way method invocation using the standard inter-ORB protocol and using a commercial, off-the-self Pentium II Xeon 400 MHz workstation running in loopback mode is ∼189 µsecs. The ORB middleware accounts for approximately 48% or ∼90 µsecs of the total roundtrip latency. Using the specialized POSIX local IPC protocol reduces roundtrip latency to ∼125 µsecs. These results illustrate that (1) DOC middleware performance is largely an implementation detail and (2) the next-generation of optimized, standards-based CORBA middleware can replace ad hoc and proprietary solutions.

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The Open Network Laboratory (ONL) is a remotely accessible network testbed designed to enable networking faculty, students and researchers to conduct experiments using high performance routers and applications. The system is built around a set of extensible, high-performance routers and has a graphical interface that enables users to easily configure and run experiments remotely. ONL's Remote Laboratory Interface (RLI) allows users to easily configure a network topology, configure routes and packet filters in the routers, assign flows or flow aggregates to separate queues with configurable QoS and attach hardware monitoring points to real-time charts. The remote visualization features of the RLI make it easy to directly view the effects of traffic as it moves through a router, allowing the user to gain better insight into system behavior and create compelling demonstrations. Each port of the router is equipped with an embedded processor that provides a simple environment for software plugins allowing users to extend the system's functionality. This paper describes the general facilties and some networking experiments that can be carried out. We hope that you and your collegues and students will check out the facility and register for an account at our web site <u>onl.arl.wustl.edu</u>

To be an effective platform for performance-sensitive real-time and embedded applications, off-the-shelf CORBA middleware must preserve communication layer quality of service (QoS) properties to applications end-toend. However, the standard CORBA's GIOPIIIOP interoperability protocols are not well suited for applications that cannot tolerate the message footprint size, latency, and jitter associated with general-purpose messaging and transport protocols. It is essential, therefore, to develop standard pluggable protocols frameworks that allow custom messaging and transport protocols to be configured flexibly and used transparently by applications.This paper provides three contributions to research on pluggable protocols frameworks for performance-sensitive communication middleware. First, we outline the key design challenges faced by pluggable protocols developers. Second, we describe how TAO, our high-performance, real-time COREAcompliant ORB, addresses these challenges in its pluggable protocols framework. Third, we present the results of benchmarks that pinpoint the impact of TAO's 00 design on its end-to-end efficiency, predictability, and scalability.Our results demonstrate how applying strategic optimizations to communication middleware can yield highly flexible/reusable designs and highly efficient/predictable implementations. In particular, the overall round-trip latency of a TAO two-way method invocation is"' 125 J.LSecs using the standard CORBA inter-ORB protocol on a commercial, off-the-self Pentium II Xeon 400 MHz workstation running in loopback mode. The ORB middleware accounts for "'60 J.LSecs of the total round-trip latency. These results illustrate that (1) communication middleware performance is largely an implementation detail and (2) the next-generation of optimized, standards-based CORBA middleware can replace ad hoc and proprietary solutions.