# A Network Analysis on Cloud Gaming: Stadia, GeForce Now and PSNow
## 4 Results
### Network Workload  
We now focus on the workload imposed on the network by users playing on cloud gaming services. We start our analysis with Figure 2, in which we show the evolution of a gaming session of around 10 min for each service. We made the corresponding packet traces available to the community at [5]. The picture reports the bitrate of the inbound traffic, due almost exclusively to the video multimedia stream. We first notice that Stadia (Figure 1(a)) has a constant bitrate, while for GeForce Now and PS Now (Figure 1(b,c respectively)), it is considerably more variable. Especially for GeForce Now, we can root this in the different video codecs, as we describe later in this section. Indeed, the application logs confirm that the variations in the bitrate are not caused by resolution adjustments or codec substitution. Looking at Stadia, the role of the video retransmission stream (green dashed line) is clear, which becomes active in the correspondence of impairments in the main video stream (solid red line). We notice a very similar behaviour in PS Now, which allows us to conjecture the presence of an analogous mechanism. We summarize the network workload, showing in Figure 3 the empirical cumulative distribution function of the video bitrate that we observe. For Stadia and GeForce Now, we report separate distributions for different video resolutions thanks to Chrome debug console and application logs, respectively. For PS Now, we only report the overall distribution as we cannot extract any statistics from the client app. As mentioned before, Stadia exhibits a rather constant bitrate (Figure 2(a)). The service allows three streaming resolutions, namely 720p, 1080p, and 4K (2160p), whose average bitrate figures are 11, 29 and 44 Mbit/s respectively. This is consistent with what is declared in documentation. [[https://support.google.com/stadia/answer/9607891](https://support.google.com/stadia/answer/9607891)]([https://support.google.com/stadia/answer/9607891](https://support.google.com/stadia/answer/9607891)), accessed on 1 October 2021. Stadia employs both H.264 and VP9 video codecs, with 4K streaming using uniquely VP9. Figure 3: Cumulative distribution of the video bitrate, for different quality video levels. (**a**) Stadia. (**b**) GeForce Now. (**c**) PS Now. Figure 2: Examples of temporal evolution of bitrate for three gaming sessions. (**a**) Stadia (1080p). (**b**) GeForce Now (1080p). (**c**) PS Now. Different is the picture for GeForce Now, shown in Figure 3b. The service allows several video resolutions, both in 16:9 and 16:10 aspect ratios. Here, we report the bitrate of the lowest (720p) and the highest (1080p) resolutions available for the 16:9 aspect ratio. Moreover, we show the 540p resolution, which is only adopted automatically in case of bad network conditions, that we trigger imposing a bandwidth limit on the testing machine. The figure shows that the bitrate has large variability, especially for 720p and 1080p. On median, 720p (1080p) consumes 15 (20) Mbit/s, which is consistent with what is declared on the system requirements of the service ([[https://www.nvidia.com/it-it/geforce-now/system-reqs/](https://www.nvidia.com/it-it/geforce-now/system-reqs/)]([https://www.nvidia.com/it-it/geforce-now/system-reqs/](https://www.nvidia.com/it-it/geforce-now/system-reqs/)), accessed on 1 October 2021). However, the interquartile ranges (IQRs) are in the order of 15 Mbit/s, much more than the 2-3 Mbit/s IQRs observed in Stadia. The bitrate reaches peaks of more than 30 and 40 Mbit/s for 720p and 1080p, respectively. Without access to the unencrypted raw video stream, we conjecture that GeForce Now makes a highly-dynamic use of the H.264 compression parameters to adapt to different video characteristics (static/dynamic scenes) and network conditions. Indeed, our experiments with limited bandwidth show that, for example, GeForce Now can sustain a 1080p video stream also with less than 15 Mbit/s available bandwidth without dropping the frame rate, likely adjusting the H.264 compression parameters.