Performance characterisation of the MCNS DOCSIS 1.0 CATV protocol with prioritised first come first served scheduling

The Multimedia Cable Networks Systems (MCNS) Data Over Cable Service Interf ace Specifications (DOCSIS) is established as the primary cable network dat a communications standard. The head-end scheduling algorithm is not defined within the standard but it is the key function for providing the required performance capability. Computer simulation, using the Common Simulation Fr amework (CSF) 12 version of the CableLabs DOCSIS 1.0 computer model, has be en used to predict the upstream system throughput and mean access delay. A prioritised first-come-first-served scheduling algorithm has been considere d to provide a baseline reference set of performance statistics against whi ch other algorithms can be compared. The simulations, with theoretical conf irmation, have shown that the maximum sustainable system throughput is 1965 kbps for a channel capacity of 2560kbps and a packet size of 1500 octets, w hereas for packet size of 100 octets the maximum sustainable throughput is only 1550kbps. The mean access delay is found to vary between 10-900ms depe nding on the offered load and assuming that the offered load does not excee d the capacity of the channel. Excess offered load causes service starvatio n according to the assigned priority.