Performance Evaluation of the "Cache-and-Forward (CNF)" Network for Mobile Content Delivery Services

This paper presents delay and throughput performance results for a "cache-and-forward" (CNF) network architecture for mobile content delivery services. The CNF network uses hop-by-hop transport and in-network storage to deliver large media files to mobile users. The CNF protocol is designed to deal with fluctuating wireless link quality and occasional periods of disconnection, and is therefore expected to be more robust and efficient than conventional TCP/IP based services. A detailed ns-2 simulation model is developed for CNF, including implementations of the reliable link layer and hop-by- hop routing protocol. The GT-ITM transit-stub with extensions for wireless access networks is used for the performance study, and network throughput and delay are measured as a function of offered traffic and radio link quality. The results show that the CNF network performance is competitive with TCP/IP even for the wired-only case, while providing significant capacity improvements as the wireless link quality degrades. It is observed that the network throughput gain for a given value of file transfer delay can be as much as ~3-5x depending on the radio link quality parameters.