A Simulation Model of the DOCSIS Protocol

Abstract

The number of households and businesses using hybrid fiber coaxial cable networks for Internet access is rapidly approaching 40 million in the United States. The cable industry has standardized on a single medium access control (MAC) and physical layer standard, the Data Over Cable Service Interface Specification (DOCSIS). The MAC layer of the emerging IEEE 802.16 broadband wireless access standard is also based upon DOCSIS. Thus, the performance of DOCSIS is now and will remain a critical element in the overall performance of shared medium broadband access networks. Despite this fact, public domain tools that may be used to assess and improve the performance of DOCSIS have been slow to emerge. To address this problem, we have implemented a simulation model of the DOCSIS MAC layer for the ` ns' network simulation tool. Due to the complexity of DOCSIS and because the specifications are purposely incomplete, developing an accurate simulation is quite challenging. In this paper we present analytic and live network evidence that the simulation accurately reflects the behavior of a DOCSIS network under a limited set of workloads.