Per-flow counting for big network data stream over sliding windows

Per-flow counting for big network data streams is a fundamental problem in various network applications such as traffic monitoring, load balancing, capacity planning, etc. Traditional research focused on designing compact data structures to estimate flow sizes from the beginning of the data stream (i.e., landmark window model). However, for many applications, the most recent elements of a stream are more significant than those arrived long time ago, which gives rise to the sliding window model. In this paper, we consider per-flow counting over the sliding window model, and propose two novel solutions, ACE and S-ACE. Instead of allocating a separate data structure for each flow, both solutions utilize the counter sharing idea to reduce memory footprint, so they can be implemented in on-chip SRAMs in modern routers to keep up with the line speed. ACE has to reset the sliding window periodically to give precise estimates, while S-ACE based on a novel segment design can achieve persistently accurate estimates. Our extensive simulations as well as experimental evaluations based on real network traffic trace demonstrate that S-ACE can achieve fast processing speed and high measurement accuracy even with a very tight memory.