End-to-End Congestion Control for Content-Based Networks

Publish/subscribe or "push" communication has been proposed as a new network service. In particular, in a content-based network, messages sent by publishers are delivered to subscribers based on the message content and on subscribers' long-term interests (subscriptions). In most systems that implement this form of communication, messages are treated as datagrams transmitted without end-to-end or in-network acknowledgments or without any form of flow control. In such systems, publishers do not avoid or even detect congestion, and brokers/routers respond to congestion by simply dropping overflowing messages. These systems are therefore unable to provide fair resource allocation and to properly handle traffic anomalies, and therefore are not suitable for large-scale deployments. With this motivation, we propose an end-to-end congestion control for content-based networks. In particular, we propose a practical and effective congestion-control protocol that is also content-aware, meaning that it modulates specific content-based traffic flows along a congested path. Inspired by an existing rate-control scheme for IP multicast, this protocol uses an equation-based flow-control algorithm that reacts to congestion in a manner similar to and compatible with TCP. We demonstrate experimentally that the protocol improves fairness among concurrent data flows and also reduces message loss significantly.