Analysis of the Early Flow Discard (EFD) discipline in 802.11 wireless LANs

Size-based scheduling improves data transfer response times by favoring flows at an early stage. Although appealing, these techniques raise concerns as they require to keep track of the volume of data sent by each and every ongoing connections and they may starve long-lived flows even if they use up limited bandwidth. Early Flow Discard (EFD) scheduling addresses these issues and we present its adaptation to infrastructure 802.11 networks where the access point downlink queue naturally builds up. To deal with this problem, EFD needs to take into account bi-directional traffic, so that it effectively controls uploads and downloads even though EFD applies to the downlink buffer only. It appears that even with limited buffers, which translates into limited memory of flows for EFD, the most simple flavor of bidirectional EFD -a simple pair of FIFO queues and tracking flow transferred volumes with a packet granularity-enables to rip the full benefit of size-based scheduling, without any of the aforementioned drawbacks.