ABC: A Simple Explicit Congestion Controller for Wireless Networks

We propose Accel-Brake Control (ABC), a simple and deployable explicit congestion control protocol for network paths with time-varying wireless links. ABC routers mark each packet with an "accelerate" or "brake", which causes senders to slightly increase or decrease their congestion windows. Routers use this feedback to quickly guide senders towards a desired target rate. ABC requires no changes to header formats or user devices, but achieves better performance than XCP. ABC is also incrementally deployable; it operates correctly when the bottleneck is a non-ABC router, and can coexist with non-ABC traffic sharing the same bottleneck link. We evaluate ABC using a Wi-Fi implementation and trace-driven emulation of cellular links. ABC achieves 30-40% higher throughput than Cubic+Codel for similar delays, and 2.2X lower delays than BBR on a Wi-Fi path. On cellular network paths, ABC achieves 50% higher throughput than Cubic+Codel

Robustness to Inflated Subscription in Multicast Congestion Control

Group subscription is a useful mechanism for multicast congestion control: RLM, RLC, FLID-DL, and WEBRC form a promising line of multi-group protocols where receivers provide no feedback to the sender but control congestion via group membership regulation. Unfortunately, the group subscription mechanism also o#ers receivers an opportunity to elicit self-beneficial bandwidth allocations. In particular, a misbehaving receiver can ignore guidelines for group subscription and choose an unfairly high subscription level in a multi-group multicast session. This poses a serious threat to fairness of bandwidth allocation. In this paper, we present the first solution for the problem of inflated subscription. Our design guards access to multicast groups with dynamic keys and consists of two independent components: DELTA (Distribution of ELigibility To Access) -- a novel method for in-band distribution of group keys to receivers that are eligible to access the groups according to the congestion control protocol, and SIGMA (Secure Internet Group Management Architecture) -- a generic architecture for key-based group access at edge routers

Smartacking: Improving TCP Performance from the Receiving End

We present smartacking, a technique that improves performance of Transmission Control Protocol (TCP) via adaptive generation of acknowledgments (ACKs) at the receiver. When the bottleneck link is underutilized, the receiver transmits an ACK for each delivered data segment and thereby allows the connection to acquire the available capacity promptly. When the bottleneck link is at its capacity, the smartacking receiver sends ACKs with a lower frequency reducing the control traffic overhead and slowing down the congestion window growth to utilize the network capacity more effectively. To promote quick deployment of the technique, our primary implementation of smartacking modifies only the receiver. This implementation estimates the sender\u27s congestion window using a novel algorithm of independent interest. We also consider different implementations of smartacking where the receiver relies on explicit assistance from the sender or network. Our experiments for a wide variety of settings show that TCP performance can substantially benefit from smartacking, especially in environments with low levels of connection multiplexing on bottleneck links. Whereas our extensive evaluation reveals no scenarios where the technique undermines the overall performance, we believe that smartacking represents a promising direction for enhancing TCP

Defeating Protocol Abuse with P4: Application to Explicit Congestion Notification

International audienceIn recent years, programmable data planes enabled by the protocol independent switch architecture (PISA) allowed the relocation of network functions closer to traffic flows and thereby the ability to react in real-time to network events. However , expressing complex and stateful network monitoring functions using state-of-the-art data plane programming languages such as P4 still remain challenging. In this context, we propose a method for modeling a stateful security monitoring function as an Extended Finite State Machine (EFSM) and express the EFSM using P4 language abstractions. We demonstrate the feasibility and benefit of our proposed approach in detecting and mitigating Explicit Congestion Notification (ECN) protocol abuse without any TCP protocol modification. Our evaluation shows that the proposed security monitoring function can restore 24.67% throughput loss caused by misbehaving TCP end-hosts while ensuring fair share of bandwidth among TCP flows