Improving The Packet Send-Time Accuracy In Embedded Devices

A number of projects deploy Linux-based embedded systems to 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 very challenging. In this paper, we present a novel network primitive, OMware, to improve the packet send-time accuracy by enabling the measurement application to pre-dispatch the packet content and its schedule into the kernel. By this pre-dispatch approach, OMware can also reduce the overheads in timestamp retrievals and sleeping, and the interference from other application processes.Our evaluation shows that OMware can achieve a microsecond-level accuracy (rather than millisecond-level in a user-space tool) in the inter-departure time of packet trains, even under heavy cross traffic. OMware also offers optimized call for sending back-to-back packet pairs, which can reduce the minimum inter-packet gap by 2 to 10 times. Furthermore, OMware can help reduce the error of replaying archived traffic from 40% to at almost 19%.