New congestion control algorithms are rapidly improving datacenters by reducing latency, overcoming incast, increasing throughput and improving fairness. Ideally, the operating system in every server and virtual machine is updated to support new congestion control algorithms. However, legacy applications often cannot be upgraded to a new operating system version, which means the advances are offlimits to them. Worse, as we show, legacy applications can be squeezed out, which in the worst case prevents the entire network from adopting new algorithms. Our goal is to make it easy to deploy new and improved congestion control algorithms into multitenant datacenters, without having to worry about TCP-friendliness with nonparticipating virtual machines. This paper presents a solution we call virtualized congestion control. The datacenter owner may introduce a new congestion control algorithm in the hypervisors. Internally, the hypervisors translate between the new congestion control algorithm and the old legacy congestion control, allowing legacy applications to enjoy the benefits of the new algorithm. We have implemented proof-of-concept systems for virtualized congestion control in the Linux kernel and in VMware's ESXi hypervisor, achieving improved fairness, performance, and control over guest bandwidth allocations. •Networks → Transport protocols; Network architectures; Programmable networks; Data center networks; Virtualized congestion control; algorithmic virtualization; datacenters; hypervisors; ECN; DCTCP; TCP. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from permissions@acm.org. ECN) . The figure plots the probability density function, over many runs, of the average goodput of each flow. The non-ECN flow is starved, reaching only 10% of the ECN goodput on average. After translation to virtual-ECN, the average goodput is near identical to that of ECN.
Congestion control from the "edge": To enable new congestion control algorithms in multi-tenant clouds, REF offers virtualized congestion control in the hypervisor.
Virtualized Congestion Control
SIGCOMM '16
Computer Science