Causal broadcasting based on sliding windows

Causal broadcasting protocols are usually implemented on top of communication subsystems which adopt a FIFO sliding window flow control using acknowledgement messages. Such messages can be source of information about the causality relations among application messages which can reduce the amount of control information necessary to guarantee causal deliveries (i.e., a vector of unbounded integer). In this paper we introduce the concept of causal window which represents the range in which all possible causal ordering violations fall. We show that, if an acknowledgement scheme is used, the size of the causal window is bounded. This allows a module implementation of the control information. A causal broadcasting protocol adopting a positive acknowledgement (PAK) scheme using credits is also presented