CRAFT: A New Secure Congestion Control Architecture

Abstract

Congestion control algorithms seek to optimally utilize network resources by allocating a certain rate for each user. However, malicious clients can disregard the congestion control algorithms and induce congestion at bottleneck links. Thus, in an adversarial environment, the network must enforce the congestion control algorithm in order to attain the optimal network utilization offered by the algorithm. Prior work protects only a single link incident on the enforcement router, neglecting damage inflicted upon other downstream links. We present CRAFT, a capability-based scheme to secure all downstream links of a deploying router. Our basic approach is to enforce a network-wide congestion control algorithm on all flows. As a reference design, we develop techniques to enforce the TCP congestion control. Our design regulates all flows to share bandwidth resources in a TCP-fair manner by emulating the TCP state machine in a CRAFT router. As a result, once a flow passes a single CRAFT router, it is TCP-fair on all downstream links of that router. Our prototype implementation shows that CRAFT provides strong fairness properties with low overhead.