ESPRES: transparent SDN update scheduling

Abstract

Network forwarding state undergoes frequent changes, in batches of forwarding rule modifications at multiple switches. Installing or modifying a large number of rules is time consuming given the performance limits of current programmable switches, which are also due to economical factors in addition to technological ones. In this paper, we observe that a large network-state update typically consists of a set of sub-updates that are independent of one another w.r.t. the traffic they affect, and hence sub-updates can be installed in parallel, in any order. Leveraging this observation, we treat update installation as a scheduling problem and design ESPRES, a runtime mechanism that rate-limits and reorders updates to fully utilize processing capacities of switches without overloading them. Our early results show that compared to using no scheduler, our schemes yield 2.17-3.88 times quicker sub-update completion time for 20th percentile of sub-updates and 1.27-1.57 times quicker for 50th percentile.