Epoch-based reconfiguration: Fast, simple, and effective dynamic network reconfiguration

Dynamic network reconfiguration is defined as the process of changing from one routing function to another while the network remains up and running. The main challenge is to avoid deadlocks and reduce packet dropping rate while keeping network service. Current approaches either require the existence of extra network resources like e.g. virtual channels, their complexity is so high that their practical applicability is limited, or they affect to the performance of the network during the reconfiguration process. In this paper we present EBR, a simple and fast method for dynamic network reconfiguration. EBR guarantees a fast and deadlock-free reconfiguration, but instead of avoiding deadlocks our mechanism is based on regressive deadlock recoveries. Thus, EBR allows cycles to be formed, and in the situation of a deadlock some packets may be dropped. However, as demonstrated, no packets need to be dropped in the working zone of the system. Also, the mechanism works in an asynchronous manner, does not require additional resources and works on any topology. In order to minimize the number of dropped packets, EBR uses an epoch marking system that guarantees that only packets potentially leading to a deadlock will be removed. Evaluation results show that EBR works efficiently in different topologies and with different routing algorithms. When compared with current proposals, EBR always gets the best numbers in all the analyzed parameters (dropped packets, latency, throughput, reconfiguration time and resources required), thus achieving the good properties of all mechanisms.