Structural and algorithmic issues of dynamic protocol update

In this paper, we study dynamic protocol update (DPU). Contrary to local code updates on-the-fly, DPU requires global coordination of local code replacements. We propose a novel solution to DPU. The key idea is to add a level of indirection between the service callers and the service provider. This indirection level facilitates an implementation of simple and efficient algorithms for DPU. For example, we describe an experimental implementation of adaptive group communication middleware. It can switch between different atomic broadcast protocols on-the-fly. All middleware protocols, including those that depend on the updated protocols, provide service correctly and with negligible delay while the global update takes places. The switching algorithm introduces very low overhead that we illustrate by showing example measurement results.