Recovery analysis of the DOCSIS protocol after service disruption

Abstract

Wide scale power outages can cause serious disruptions to digital services over community antenna television (CATV) networks. This can result in long service recovery times for some or all of the cable modems (CMs). In this paper, the recovery mechanisms of the Data Over Cable Service Interface Specification (DOCSIS) protocol, due to service disruption, are studied. We propose a new scheme for the ranging of modems, namely persistent ranging algorithm (PRA) and two different simulation models have been developed for this purpose. The simulation results show that the static nature of the registration and initialization parameters can introduce an excessive delay in the recovery time of the system. Minimum recovery times of 820 s and 975 s (two ranging opportunities/second) for network architectures with 400 CMs and 500 CMs, respectively, on a single upstream channel were obtained. In order to validate the accuracy of the simulation models a set of experiments was performed on a CATV network testbed. The testbed results revealed that the simulation models produced are realistic and offer reliable estimates of large-scale network topologies. Extensions to the DOCSIS MAC protocol in which the status of the system prior to disruption is used have reported a decrease of up to 42% in the recovery time of the system.