Protocol enhancements for intermittently connected hosts

Abstract

Internet users are increasingly mobile. Their hosts are often only intermittently connected to the Internet, due to using multiple access networks, gaps in wireless coverage or explicit user choice. When such hosts communicate using the current Internet protocols, intermittent connectivity can significantly decrease performance and even cause connections to fail altogether. This paper experimentally measures the behavior of Internet communication across a dynamically changing, intermittently connected path. An analysis of the experimental results finds that address changes together with transport-layer timeout and retransmission behaviors are the main limiting factors. Based on these experimental results, this paper proposes a solution that combines the Host Identity Protocol (HIP) with two new protocol enhancements, the TCP User Timeout Option and the TCP Retransmission Trigger. Detailed experiments with HIP and a prototype implementation of these protocol enhancements show that they tolerate address changes and arbitrary-length disconnections while significantly increasing performance under intermittent connectivity to within 86-96% of a scenario with constant connectivity.