# A Network Analysis on Cloud Gaming: Stadia, GeForce Now and PSNow
## 4 Results
### Location of Gaming Machines  
This section provides a preliminary investigation of the cloud gaming infrastructure regarding the number and location of game servers and employed domains, as observed from our location. This can be useful to identify cloud gaming traffic for, e.g., traffic engineering or content filtering.  
We first focus on the remote gaming machines, analyzing when the server IP addresses the client applications contact, summarized in Table 3. Indeed, after the initial setup phase, the client exchanges traffic (almost) uniquely with a single server where the gaming is likely executed (we cannot infer if the server IP address acts as an ingress load balancer or reverse proxy). Considering Stadia, at each session, we contacted a different server--i.e.,  
Figure 6: Example of quality-level reduction in Stadia, in terms of frame rate and video resolution subsequent to packet losses.  
we performed 74 sessions and reached 74 different server IPs. They lay on 22 subnets/24, all belonging to the Google 15129 AS (we map an IP address to the corresponding AS using an updated RIB from [[http://www.routeviews.org/](http://www.routeviews.org/)]([http://www.routeviews.org/](http://www.routeviews.org/)) accessed on 13 January 2021). Different is the case for GeForce Now and PS Now, for which in roughly 50% of the cases, we contacted a server IP we had already observed. GeForce Now servers lay on 23 subnets belonging to three different ASes, all controlled by NVIDIA. Recall that we used all the 14 available NVIDIA data centres in our experimental campaign by instrumenting the client application. Finally, all 36 server IPs for PS Now belong to only 2 subnets/24 from the 33353 Sony AS. In terms of latency, additional ping measures show that Stadia and PS Now servers are 6-8 ms away from our location, with Central European GeForce Now in the order of 15-20 ms. However, we cannot link this to the service quality or infrastructure deployment, since we perform measurements from a single vantage point. We did not qualitatively observe a significant lag between users' commands and game response without traffic shaping.  
Finally, we analyze the domains that the applications contact during the gaming sessions. We extract them by inspecting the client's domain name system (DNS) queries, before opening a new connection and extracting the Server Name Indication (SNI) field from the Transport Layer Security Security (TLS) Client Hello messages. In the case of Stadia, we only find stadia.google.com as domain-specific to this service. Indeed, the client application contacts a dozen of other domains, but those are shared with all Google services (e.g., gstatic.com and googleapis.com), and, as such, they are not specific of Stadia. Regarding GeForce Now, the application contacts the general nvidia.com domain as well as the more specific nvidiagrid.net. Finally, PS Now relies on the playstation.com and.net domains and their sub-domains, which are, thus, not specific to the PS Now service. Interestingly, GeForce Now is the only service that uses domains to identify gaming machines, using subdomains of cloudmatchbeta.nvidiagrid.net. Indeed, for the other services, the domains that we find are associated uniquely with the control servers--used for login, static resources, etc.--while gaming machines are contacted without a prior DNS resolution.  
_Take away: We seldom observe repeated IP addresses of the gaming machines for the three services. They are all located in the AS of the respective corporate. GeForce Now is the only one that identifies gaming machines via DNS domain names._