Most of the current active queue management (AQM) designs have major issues including severe hardship of being tuned for highly fluctuated cellular access link bandwidths. Consequently, most of the cellular network providers either give up using AQMs or use conservative offline configurations for them. However, these choices will significantly impact the performance of the emerging interactive and highly delay sensitive applications such as virtual reality and vehicle-to-vehicle communications. Therefore, in this paper, we investigate the problems of existing AQM schemes and show that they are not suitable options to support ultra-low latency applications in a highly dynamic network such as current and future cellular networks. Moreover, we believe that achieving good performance does not necessarily come from complex drop rate calculation algorithms or complicated AQM techniques. Consequently, we propose BoDe an extremely simple and deployment friendly AQM scheme to bound the queuing delay of served packets and support ultra-low latency applications. We have evaluated BoDe in extensive trace-based evaluations using cellular traces from 3 different service providers in the US and compared its performance with state-of-the-art AQM designs including CoDel and PIE under a variety of streaming applications, video conferencing applications, and various recently proposed TCP protocols. Results show that despite BoDe's simple design, it outperforms other schemes and achieves significantly lower queuing delay in all tested scenarios.
Explicit congestion notification (ECN) is another technique used to do the buffer management indirectly. In other words, ECN-based approaches, use modified switches to tag certain packets and explicitly notify the senders about congestion in the network. Later, senders need to adjust their sending rates to reduce queue occupancy and congestion in the network. ABC @cite_19 is a recent example of ECN-based approach proposed for cellular networks. However, there are two key issues with all ECN-based approaches. First, to employ these approaches in practice, application (or network-stack) at the client server need to be modified to process the ECN bits set by the switches and change the sending rates accordingly. This means that for TCP-based applications, a Kernel patch at all sources destinations is required. The problem becomes worst for UDP-based applications (such as Skype, QUIC @cite_28 etc.) that manage the congestion in the application layer. This means that all these UDP-based applications need to be modified to use the ECN-bits which is not a deployment friendly solution. The second issue is the fact that the network service providers are usually not interested in exposing their network's states (queue occupancy, queue delay, etc.) required by ECN-based schemes to the end-users.
@cite_28 @cite_19
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We present our experience with QUIC, an encrypted, multiplexed, and low-latency transport protocol designed from the ground up to improve transport performance for HTTPS traffic and to enable rapid deployment and continued evolution of transport mechanisms. QUIC has been globally deployed at Google on thousands of servers and is used to serve traffic to a range of clients including a widely-used web browser (Chrome) and a popular mobile video streaming app (YouTube). We estimate that 7 of Internet traffic is now QUIC. We describe our motivations for developing a new transport, the principles that guided our design, the Internet-scale process that we used to perform iterative experiments on QUIC, performance improvements seen by our various services, and our experience deploying QUIC globally. We also share lessons about transport design and the Internet ecosystem that we learned from our deployment. We propose Accel-Brake Control (ABC), a protocol that integrates a simple and deployable signaling scheme at cellular base stations with an endpoint mechanism to respond to these signals. The key idea is for the base station to enable each sender to achieve a computed target rate by marking each packet with an "accelerate" or "brake" notification, which causes the sender to either slightly increase or slightly reduce its congestion window. ABC is designed to rapidly acquire any capacity that opens up, a common occurrence in cellular networks, while responding promptly to congestion. It is also incrementally deployable using existing ECN infrastructure and can co-exist with legacy ECN routers. Preliminary results obtained over cellular network traces show that ABC outperforms prior approaches significantly.