Reconciling the characteristics of wired and wireless networks: the Janus approach

The Janus project aims to develop methodologies and protocols to support multiway communications in hybrid wireless and land-line networks. Significant differences in performance and qualitative attributes between wired and wireless networks necessitate adaptation and arbitration mechanisms in order to deliver group transport services. Janus provides a proxy mechanism to reconcile differences between the wired and wireless domains, incorporate synchronization algorithms to prevent delivery lags caused by high network variability, and anticipate and take appropriate actions when approaching (or when within) "trouble spots" or dead zones that are intrinsic to wireless networks. These adaptive mechanisms are implemented in software capable of executing on devices ranging from hand-helds to laptops to desktops, and manifested as libraries that provide group communication facilities at different levels of data delivery semantics. A discussion of unique challenges in hybrid wired and wireless networks, a description of the Janus active middleware architecture, and preliminary results and experiences are presented in this paper.