The New AQM Kids on the Block: Much Ado About Nothing?

Abstract

Active Queue Management (AQM) design has again come into the spotlight of network operators, vendors and OS developers. This reflects the growing concern and sensitivity about the end-to-end latency perceived by today’s Internet users. Indeed, delays on the order of seconds have become common due to the deployment of excessively-sized FIFO/DropTail buffers at the edge of many networks. CoDel and PIE are two AQM mechanisms that have recently been presented and discussed at the IRTF and the IETF. However, to the best of our knowledge, they have not yet been thoroughly evaluated or compared against each other except by simulation. We set thus to perform an experimental evaluation using real-world implementations, in both wired and wireless testbeds. We have in addition compared them with a decade-old variant of RED called Adaptive RED, which shares with CoDel and PIE the goal of “knob-free” operation. Surprisingly, in many instances results were much more favorable towards Adaptive RED. We do not call into question the need for new AQMs, however, there are lessons yet to be learned from old designs.