# Evaluating MPTCP Congestion Control Algorithms: Implications for Streaming in Open Internet
## 4 Conclusions  
The paper's objective was to assess the effectiveness of popular MPTCP CC algorithms, specifically LIA, OLIA, BALIA, and wVegas, in conveying delay-sensitive content for streaming-oriented applications. The algorithms were tested in the open Internet connectivity with performance quantified through objective measures of protocol delay, Path Delay, mean drop rate, throughput, and HoL blocking. LIA paired with BBR at the path level and BALIA with Reno ensured a low mean drop rate and high throughput. BALIA when paired with either BBR or Reno, also achieved the lowest HoL Blocking Degree, which translates to a reduced waiting time for the stream reassembly at the receiver, hence, an enhanced user experience regarding multimedia traffic.  
From the perspective of Path Delay, the combination of wVegas and Reno, as well as OLIA and BBR, emerged as the most efficient ones, offering the lowest latency and jitter, which is paramount for real-time applications. In terms of the protocol delay, LIA with BBR displayed the highest average, while the combination of wVegas and Reno was much less efficient. BALIA paired with Reno proved to be the most attractive with respect to bandwidth utilization, making it a primary choice for high-resolution streaming.  
Overall, LIA with BBR appears to be the best choice for the applications where packet loss is most detrimental. In contrast, OLIA paired with BBR and BALIA combined with Reno are adequate for bandwidth-intensive ones. The lower HoL degree achieved by BALIA, when paired with either Reno or BBR, is especially beneficial for streaming involving resource-constrained devices, like mobile appliances.  
However, one should recognize that the common MPTCP and SPTCP algorithms evaluated in this study have inherent limitations when considered in the context of real-time and streaming services. Their primary design objectives, i.e., to maximize throughput while maintaining fairness, may not always align with the requirements of delay-sensitive applications. This realization underscores the need to develop new MPTCP CC algorithms. These new algorithms should address the unique challenges of streaming systems, particularly HoL blocking and delay variability.  
Conceptualization, P.I. and M.M.; methodology, P.I., M.M. and L.P.L.; software, M.M. and L.P.L.; validation, L.P.L. and P.I.; formal analysis, L.P.L. and P.I.; investigation, L.P.L. and P.I.; resources, L.P.L.; data curation, L.P.L.; writing--original draft preparation, L.P.L.; writing--review and editing, P.I. and M.M.; visualization, L.P.L.; supervision, P.I.; project administration, P.I.; funding acquisition, P.I. All authors have read and agreed to the published version of the manuscript.  
This work has been performed in the framework of the project \"Robust control solutions for multi-channel networked flows\" no. 2021/41/B/ST/00108 financed by the National Science Centre, Poland.  
No application.  
This work has been completed while the first author was the Doctoral Candidate in the Interdisciplinary Doctoral School at the Lodz University of Technology, Poland.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.