# On Cross-Layer Interactions for Congestion Control in the Internet
## 2 Related Work  
The problem of congestion control is widely discussed in many research papers. The majority of them are focused on a specific key component of the Internet mechanisms evaluated with the assumption that other key components remain unchanged. Moreover, the presented analyses are usually oriented towards a specific purpose, e.g., the buffer size influence or impact of the network heterogeneity on different aspects of transmission performance. Suffic it to mention several papers related to the evaluation of TCP versions assessed in this paper in conjunction with the Drop Tail (DT) mechanism. The authors of [4] explore the fairness of high-speed TCPs. The broader comparison of high-speed TCPs over the high-BDP network is drawn by [PERSON] et al. [5]. In [6], the authors study the interactions between multiple versions of TCP. Another comparison of multiple TCP versions (Cubic and New Reno) in various network scenarios (wired/wireless) is presented in [7]. The authors of [8] perform a similar evaluation concerning Linux versions of TCPs. The analytical tool to compare the TCP versions evaluated in this paper is submitted in [9]; the simulation results and performance analysis are reported in [10]. In this paper, we focus on two AQMs: PIE and CoDel. The comparison of those state-of-the-art AQMs' limits and hints for tuning and improvement are presented in [11]. The authors also provide a discussion concerning the operational range of both algorithms. The assessment of the introduced delay and bandwidth utilization provided by three different AQMs, namely, ARED, PIE, and CoDel for the sender using TCP Cubic, in the presence of CBR-traffic, is studied in [12]. Different queuing mechanisms, in the presence of TCP Reno, are also evaluated in [13]. A few papers evaluate the cross-layer interaction between end-to-end TCP congestion control and buffer management strategies provided by AQM. In [14], the performance of AQMs in the presence of new versions of the TCP congestion control mechanism is evaluated. The paper focuses on TCP SACK, New Reno, FACK, and Cubic versions and compares RED, AVQ, PI, REM, and AN-AQM along with DT approach. All the evaluated AQM algorithms, although thoroughly discussed and analyzed in many research papers, are not commonly used in commercial buffers due to configuration issues; they do not fall into the category of recommended by RFC 7567 [3] AQMs algorithms. In this paper, the recommended CoDel and PIE are verified against the most widespread TCP versions. The authors of [15] evaluate RED, PIE, and CoDel, however in combination with TCP Reno, BIC, and Vegas, which are rather less popular TCP flavors. Moreover, the authors use a very simple, real-time testbed consisting of a client, router, and server. The client sends data to the server via the router, and the receiver sends back ACKs via the same router. The results are obtained based on one generated flow. The outcomes presented in this paper are based on a much more diversified and extensive set of simulation scenarios and more common TCP versions. In the assumptions, those nearest to this paper's work are presented in [16]. The authors perform a cross-comparison of eight TCP flavors and five AQM variants in several network scenarios. The most significant differences concern network configuration, i.e., link capacity, MTU, as well as the selection of RTT distribution. The authors restrain the bottleneck link to 10 Mbps and MTU to 500 B. Assuming TCP Cubic and Compound were designed for more demanding environments (high speed and high latency) in 10 Mbps simulation, their expected superiority may not be visible. Moreover, the smaller MTU shortens the experienced delay in low-speed networks, however, leads to network under-utilization, especially in high-speed environments. In this paper, the TCP-AQM interactions are evaluated in the Data Center scenario with 1 Gbps links and the Access Link scenario with bandwidth set to 100 Mbps. In both scenarios, a 1500 B MTU is used.