Improving the packet send-time accuracy in embedded devices

Abstract

A number of projects deploy Linux-based embedded systemsto carry out large-scale active network measurement and network experiments.Due to resource constrains and the increase of network speed,obtaining sound measurement results from these low-end devices is verychallenging. In this paper, we present a novel network primitive, OMware,to improve the packet send-time accuracy by enabling the measurementapplication to pre-dispatch the packet content and its schedule into thekernel. By this pre-dispatch approach, OMware can also reduce the overheadsin timestamp retrievals and sleeping, and the interference fromother application processes.Our evaluation shows that OMware can achieve a microsecond-levelaccuracy (rather than millisecond-level in a user-space tool) in the interdeparturetime of packet trains, even under heavy cross traffic. OMwarealso offers optimized call for sending back-to-back packet pairs, whichcan reduce the minimum inter-packet gap by 2 to 10 times. Furthermore,OMware can help reduce the error of replaying archived traffic from40% to at almost 19%