Ajil: Distributed Rate-limiting for Multicast Networks

Multicast traffic patterns play a key role in dependable data centers, arising when data is replicated and distributed over multiple machines for fault-tolerance and availability. Such settings involve large numbers of multicast groups as well as multiple senders to each group — a single system can have hundreds of such multicast channels. Without ef- fective multi-channel rate control, multicast senders cannot determine the right rate to send data at and often transmit to groups as fast as possible. As a result, multicast chan- nels are subject to traffic spikes that can overload individual end-hosts within the data center as well as its communica- tion back-plane. This paper introduces and evaluates Ajil, a distributed rate-limiting protocol for data centers. Ajil enforces a system-wide quota on multicast traffic, and fa- cilitates equitable distribution of this quota across all the multicast channels in the data center.