The last several years has seen a renewed interest in smart queue management to curb excessive network queueing delay, as people have realised the prevalence of bufferbloat in real networks. However, for an effective deployment at today's last mile connections, an improved queueing algorithm is not enough in itself, as often the bottleneck queue is situated in legacy systems that cannot be upgraded. In addition, features such as per-user fairness and the ability to de-prioritise background traffic are often desirable in a home gateway.In this paper we present Common Applications Kept Enhanced (CAKE), a comprehensive network queue management system designed specifically for home Internet gateways. CAKE packs several compelling features into an integrated solution, thus easing deployment. These features include: bandwidth shaping with overhead compensation for various link layers; reasonable DiffServ handling; improved flow hashing with both per-flow and per-host queueing fairness; and filtering of TCP ACKs. Our evaluation shows that these features offer compelling advantages, and that CAKE has the potential to significantly improve performance of last-mile internet connections.
Among the state of the art algorithms in modern queue management, is the FQ-CoDel algorithm @cite_4 . FQ-CoDel implements a hybrid AQM fairness queueing scheme which isolates flows using a hashing scheme and schedules them using a Deficit Round-Robin (DRR) @cite_13 scheduler. In addition, FQ-CoDel contains an optimisation that provides implicit service differentiation for sparse (low-bandwidth) flows, similar to @cite_0 @cite_8 . Evaluations of FQ-CoDel have shown that it achieves low queueing latency and high utilisation under a variety of scenarios @cite_6 @cite_5 .
@cite_4 @cite_8 @cite_6 @cite_0 @cite_5 @cite_13
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This memo presents the FQ-CoDel hybrid packet scheduler and Active Queue Management (AQM) algorithm, a powerful tool for fighting bufferbloat and reducing latency. FQ-CoDel mixes packets from multiple flows and reduces the impact of head-of-line blocking from bursty traffic. It provides isolation for low-rate traffic such as DNS, web, and videoconferencing traffic. It improves utilisation across the networking fabric, especially for bidirectional traffic, by keeping queue lengths short, and it can be implemented in a memory- and CPU-efficient fashion across a wide range of hardware. Several new active queue management (AQM) and hybrid AQM fairness queueing algorithms have been proposed recently. They seek to ensure low queueing delay and high network goodput without requiring parameter tuning of the algorithms themselves. However, extensive experimental evaluations of these algorithms are still lacking. This paper evaluates a selection of bottleneck queue management schemes in a test-bed representative of residential Internet connections of both symmetrical and asymmetrical bandwidths as well as WiFi. Latency under load and the performance of VoIP and web traffic patterns are evaluated under steady state conditions. Furthermore, the impact of the algorithms on fairness between TCP flows with different RTTs, and also the transient behaviour of the algorithms at flow startup is examined. The results show that while the AQM algorithms can significantly improve steady state performance, they exacerbate TCP flow unfairness. In addition, the evaluated AQMs severely struggle to quickly control queueing latency at flow startup, which can lead to large latency spikes that hurt the perceived performance. The fairness queueing algorithms almost completely alleviate the algorithm performance problems, providing the best balance of low latency and high throughput in the tested scenarios. However, on WiFi the performance of all the tested algorithms is hampered by large amounts of queueing in lower layers of the network stack inducing significant latency outside of the algorithms' control. The availability of cheaper and high capacity Random Access Memory (RAM) has resulted in the growth of buffer size in all the computing devices. This aberrant increase of buffer capacity in network devices has resulted into high latency, leading to reduced throughput; thus decreasing the tendency of absorbing spontaneous burst of traffic. The requirement for Active Queue Management (AQM) has been evident for decades. These solutions require various parameter configuration and are dependent on a particular network condition to work efficiently. Hence an algorithm which is simple, efficient, does not require setting of parameters and works seamlessly irrespective of the network condition is required. Even though Controlled Delay (CoDel) is parameterless and adapts to dynamically changing link rates with no negative impact on utilization, it deviates from its primary purpose of reducing congestion when there is an increase in RTT and when congestion level varies abruptly. As a consequence, a variant of CoDel called Stochastic Fair Queue CoDel (sfqCoDel) is simulated and compared. The Stochastic Fair Queue CoDel proactively drops packets which occupy reasonably larger bandwidth as compared to CoDel, which proactively drops packet irrespective of the bandwidth consumption by packets. This paper aims to perform a comprehensive analysis of Stochastic Fair Queue CoDel for Active Queue Management. A comparison is also carried out between sfqCoDel with CoDel. The sfqCoDel appears to be much better than CoDel in certain areas where CoDel fails to perform well. Several high-speed TCP variants are adopted by end users and therefore, heterogeneous congestion control has become the characteristic of newly emerging high-speed optical networks. In contrast to homogeneous TCP flows, fairness among heterogeneous TCP flows now depends on router parameters such as queue management scheme and buffer size. To the best of our knowledge, this is the first study of fairness performance among heterogeneous TCP variants over a 10 Gbps high-speed optical network environment. Our evaluation scenarios for heterogeneous TCP flows consist of TCP variants with substantial presence in current Internet; therefore, TCP-SACK, CUBIC TCP (CUBIC) and HighSpeed TCP (HSTCP) compete for bottleneck bandwidth. Experimental results for fairness are presented for different queue management schemes, such as Drop-tail, Random Early Detection (RED), CHOose and Keep for responsive flows CHOose and Kill for unresponsive flows (CHOKe), and Approximate Fair Dropping (AFD), with varying degree of buffer sizes. We observe heterogeneous TCP flows induce more unfairness than homogeneous ones. Active queue management (AQM) schemes, RED, CHOKe, and AFD, improve fairness for large buffer sizes as compared to Drop-tail, whereas AQM schemes lose the fairness advantage for small buffer sizes. This study provides preliminary results for fairness challenges to deploy all-optical routers with limited buffer size.