A framework for protocol composition in Horus

Abstract

The Horus system supports a communication architecture that treats protocols as instances of an abstract data type. This approach encourages developers to partition complex protocols into simple microprotocols, each of which is implemented by a protocol layer. Protocol layers can be stacked on top of each other in a variety of ways, at run-time.First, we describe the classes of protocols that can be supported this way.Next, we present the Horus object model that we designed for this technology, and the interface between the layers that makes it all work.We then present an example layer that implements a group membership protocol. Next, we show how, given a set of required properties, an appropriate stack can be constructed. We look at an example stack of protocols, which provides fault-tolerant, totally ordered communication between a group of processes. The work contributes a standard framework for protocol development and experimentation, provides a high performance implementation of the virtual synchrony model, and introduces a methodology for increasing the robustness of the protocol development process.

Masking the overhead of protocol layering

“…Unfortunately, the code is slow compared to corresponding C code. Nevertheless, between two SunOS user processes on two Sparc 20s connected by a 140 Mbit/sec ATM network, we achieve a roundtrip latency of 170 seconds using the PA, down from about 1.5 milliseconds in the original C version of Horus [12].…”

On composability of localization protocols for wireless sensor networks

“…Horus [7], for example, is based on a vertical stack of protocols, where the events are strictly passed from one layer to the adjacent one. A non-hierarchical protocol composition framework is JGroup/ARM [8].…”

Masking the overhead of protocol layering

“…The PA eliminates both overheads almost entirely, and has resulted in one to This work was supported by ARPA/ONR grant N00014-92-J-1866 three orders of magnitude of latency improvement o v er existing protocol implementations. For example, we are using it on an Objective Caml (O'Caml) [8] implementation of Horus [13,12]|a software framework that supports the layering of general group communication protocols 1 . O'Caml is an object-oriented dialect of ML [9], a high-level, concise, garbage-collected language, that allows to develop complex protocols quickly and relatively error-free.…”