Geosynchronous satellite (GEO) networks are a crucial option for users beyond terrestrial connectivity. However, unlike terrestrial networks, GEO networks exhibit high latency and deploy TCP proxies and traffic shapers. The deployment of proxies effectively mitigates the impact of high network latency in GEO networks, while traffic shapers help realize customer-controlled data-saver options that optimize data usage. It is unclear how the interplay between GEO networks' high latency, TCP proxies, and traffic-shaping policies affects the quality of experience (QoE) for commonly used video applications. To fill this gap, we analyze the quality of over $2$k YouTube video sessions streamed across a production GEO network with a $900$Kbps shaping rate. Given the average bit rates for the selected videos, we expected seamless streaming at $360$p or lower resolutions. However, our analysis reveals that this is not the case: $28\%$ of TCP sessions and $18\%$ of gQUIC sessions experience rebuffering events, while the median average resolution is only $380$p for TCP and $299$p for gQUIC. Our analysis identifies two key factors contributing to sub-optimal performance: (i)unlike TCP, gQUIC only utilizes $63\%$ of network capacity; and (ii)YouTube's imperfect chunk request pipelining. As a result of our study, the partner GEO ISP discontinued support for the low-bandwidth data-saving option in U.S. business and residential markets to avoid potential degradation of video quality -- highlighting the practical significance of our findings.

翻译：地球同步轨道（GEO）卫星网络是缺乏地面连接用户的关键选择方案。然而，与地面网络不同，GEO网络存在高延迟特征，并部署了TCP代理和流量整形器。代理的部署有效缓解了GEO网络高延迟的影响，而流量整形器则有助于实现用户可控的数据节约选项以优化数据使用。目前尚不清楚GEO网络的高延迟、TCP代理与流量整形策略之间的相互作用如何影响常用视频应用的服务质量（QoE）。为填补这一空白，我们分析了在传输速率为900Kbps的生产级GEO网络上流传输的2000余个YouTube视频会话质量。根据所选视频的平均比特率，我们预期在360p及以下分辨率可实现无缝流媒体传输。然而分析结果表明实际情况并非如此：28%的TCP会话和18%的gQUIC会话发生了缓冲事件，平均分辨率中位数在TCP下仅为380p，gQUIC下为299p。我们的分析确定了导致性能欠佳的两个关键因素：(i)与TCP不同，gQUIC仅利用了63%的网络容量；(ii)YouTube不完善的分块请求流水线机制。基于本研究结论，合作GEO互联网服务提供商已在美国商业和住宅市场停用了低带宽数据节约选项以避免潜在视频质量劣化——这凸显了我们研究结论的实际价值。