The Design and Performance of a Pluggable Protocols Framework for Object Request Broker Middleware

Abstract

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-to-end. However, the standard CORBA’s 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 communication middleware. First, we outline the key design challenges faced by pluggable protocols developers. Second, we describe how TAO, our high-performance, real-time CORBAcompliant ORB, addresses these challenges in its pluggable protocols framework. Third, we present the results of benchmarks that pinpoint the impact of TAO’s OO design on its endto-end efficiency, predictability, and scalability. Our results demonstrate how applying 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 using the standard inter-ORB protocol and using a commercial, off-the-self Pentium II Xeon 400 MHz workstation running in loopback mode is 125 secs. The ORB middleware accounts for approximately 48% or 60 secs of the total round-trip latency. These results illustrate that (1) communication middleware performance is largely This work was supported in part by Boeing, DARPA contract 9701516, GDIS, NSF grant NCR-9628218, Nortel, Siemens, and Sprint. an implementation detail and (2) the next-generation of optimized, standards-based CORBA middleware can replace ad hoc and proprietary solutions. Subject areas: Frameworks; Design Patterns; Distributed and Real-Time Systems