Abstract-TheRADclock is an open source software clock that is highly robust to latency variability. A limitation up to now has been that it could only be used with NTP servers, and was unable to take advantage of IEEE-1588 enabled devices, including PTP masters and NICs with hardware timestamping. This paper benchmarks an early implementation of PTP support for RADclock, with and without hardware timestamping. We evaluate performance under both nominal and stressed conditions against alternative software clients ptpd and timekeeper and find that it compares very well.

International audienceInternet access everywhere has become a reality today, largely thanks to the deployment of numerous WiFi hotspots. However, controlling user access to the network remains a challenge because of the need for specific hardware and the lack of software standards. Using the OpenFlow protocol, we provide a new extensible way of designing and managing guest access architectures in the Cloud. We demonstrate the feasibility of such an architecture, with little impact on existing configurations when using virtual machines and Software Defined Networks. Our results can be used to build a real life testbed to test new mutualized guest access network architecture and improve hardware interoperability

Abstract-Dealing effectively with latency is the key to accurate and reliable timekeeping over networks. Software components of timekeeping, including synchronisation algorithms such as ntpd, RADclock, and ptpd, must deal with the significant and highly variable latencies inherent to common operating systems. Using the DTrace system profiling tool, we provide an accurate breakdown of the latencies between common timestamping locations in the FreeBSD Operating System. We report on how these latency components react to stress patterns of different kinds, and determine which timestamping strategies result in the lowest latency, and the smallest in-host asymmetry. Our results can be used to improve timestamping and timekeeping for software clocks.