## 2 Related Work
### High-Quality P2P Video Streaming Systems  
The central challenge for high-quality P2P video streaming systems lies in simultaneously meeting real-time, reliability, and security requirements within a decentralized environment. Researchers primarily explore three directions to achieve this: transport protocol optimization, network topology management, and Quality of Service assurance. The Celerity system serves as a prime example in this domain, designed for multi-party audio-video conferencing scenarios [36]. It utilizes an intelligent overlay construction algorithm, leveraging Round-Trip Time (RTT) and geographical distance to preferentially cluster nearby nodes. This is further coupled with machine learning analysis of historical link data to predict potential congestion and proactively adjust routing. By employing an anycast strategy, Celerity dynamically selects the path with the minimum end-to-end latency among multiple available options, thereby significantly enhancing video quality and user experience in large-scale conferencing environments. Complementing such topological advancements is the strategic choice and optimization of the underlying transport protocol. The Secure Reliable Transport (SRT) protocol directly enhances UDP's low-overhead advantages by incorporating selective retransmission, effectively avoiding the head-of-line blocking issue prevalent in TCP [16; 37]. SRT maintains stable throughput through dynamic congestion control, adaptive buffering, and intelligent traffic shaping. Furthermore, its design integrates end-to-end AES encryption, which, combined with enhanced ARQ and Forward Error Correction (FEC), robustly ensures data integrity and security. A key feature, the latency-tolerating window mechanism, allows the system to wait for packet retransmissions within a millisecond-level timeframe, enabling low-jitter real-time playback. In the context of a chain-based P2P topology, these intrinsic SRT characteristics not only alleviate the load on individual nodes but also maintain high-quality video transmission across multi-hop paths, thereby laying a robust technical foundation for scalable decentralized streaming systems. As shown in Table 1, most existing P2P and hybrid systems exhibit higher end-to-end latency and slower recovery from failures, especially under dynamic network conditions or node churn. For example, SmoothCache and ALIVE, while effective in reducing server load, rely on mesh or hybrid topologies that introduce significant signaling and coordination overhead, resulting in recovery times exceeding 3 s and packet loss spikes above 1%. ReputeStream and Celerity improve resilience through reputation and overlay optimization but still suffer from multi-second recovery and non-negligible failure rates in large-scale or high-churn scenarios. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**System** & **Topology** & **Latency (ms)** & **Recovery Time (s)** & **Failure Rate/Packet Loss** \\ \hline SmoothCache [31] & Mesh/Hybrid & 800–1200 & \(>\)5 & \(\sim\)2\% (burst) \\ ALIVE [28; 32] & Hybrid (P2P + Edge) & 400–900 & 3–5 & \(\sim\)1\% \\ ReputeStream [7] & Multi-layer P2P & 300–700 & 3–4 & \(>\)1\% (under churn) \\ Celerity [36] & Mesh & 250–600 & 2–4 & \(\sim\)1\% \\ Proposed (Chain + SRT) & Chain & 200–700 & 0.8–1.5 & \(<\)0.2\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of representative P2P and hybrid video streaming systems. In contrast, the proposed chain-topology system, leveraging SRT and intelligent self-healing, achieves sub-second delays and maintains packet loss below 0.5% even in multi-hop deployments. The chain structure minimizes the number of control messages and simplifies failure localization, enabling rapid relay path reconstruction. SRT's selective retransmission and adaptive buffering further reduce latency and loss compared with TCP-based or mesh solutions.