MNTP: Enhancing Time Synchronization for Mobile Devices.

ABSTRACTClock synchronization between Internet hosts is important in a variety of applications including gaming, finance and measurement. While clock synchronization issues in wireline networks have been well studied, mobile hosts present challenges that have not received as much attention. In this paper, we describe a study of clock synchronization in mobile hosts, which often implement a simplified version of the Network Time Protocol (NTP), known as SNTP, due to resource constraints typical of mobile devices. We begin by reporting an analysis of logs from NTP servers that highlights the significant differences in synchronization behavior of wireline vs. wireless hosts. This analysis motivates a laboratory-based study of the details of clock synchronization on mobile hosts, which reveals the causes and extent to which synchronization can become misaligned. We then describe a new protocol that we call Mobile NTP (MNTP), which is designed to be simple, efficient and easy to deploy. We implement MNTP on a wireless laptop and demonstrate its capability over a range of operating conditions. We find that MNTP maintains clock synchronization to within 25ms of a reference clock, which is over 12 times better than standard SNTP.