## 4 Experimental Setup and Procedures
### Experimental Setup  
To eliminate the influence of the Internet traffic and ensure replicability, all experiments took place in a dedicated local network environment at the home institution of the authors.  
The topology of the network is shown in Figure 6 and details about the used devices can be found in Table 1. The shortcuts used for the devices include those introduced in Section 1 and Figure 1 (SRV, PC, PH and HL).  
All experiments used up to 20 PC, one SRV server and one SWCH switch. The experiments from the E.6 DF set also used one PH and the ones from the E.HL set one HL. Of course, the wireless router (WiFi) was needed for E.6 DF and E.HL experiments, too. Each client device, that is PC, PH and HL, ran one instance of a web browser with one instance of a virtual scene (VS), used for the experiments. This means that each client device represented one user in the shared VS. There were no other software processes running on the client devices, except for the ones belonging to the operating system. The PC devices used Google Chrome browser version 85 and the smartphone (PH) used Google Chrome Canary version 70. The MS HoloLens device HL used its built-in version of the MS Edge browser. The server computer SRV ran one instance of a web server, providing the shared VS and NAF, and one instance of the Google Chrome browser version 86, with the ECA dashboard page. On each PC, the virtual scene was rendered in the windowed  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Label** & **Type** & **Model or Configuration** \\ \hline WiFi & Wireless router & Mercusys MW 325R \\ \hline SWCH & Ethernet switch & Cisco Catalyst 2960-X series \\ \hline SRV & Server computer & Intel® CoreTM 17-9700F 3 GHz CPU; \\  & & 16 GB RAM; Crucial BX500 HDD; \\  & & NVIDIA GeForce GTX 1650 GPU; Full HD display; \\  & & Windows Server 2019 Standard OS; \\  & & Node;js ver.14.10.1; Express.js ver.4.17.1; \\  & & Socket.I0 2.3.0; \\ \hline PC & Personal computer & Intel® CoreTM 15-4590 3.3 GHz CPU; \\  & & Intel HD Graphics 4600 GPU; Full HD display; \\  & & 4 GB RAM; Seagate Barracuda 7200.12 HDD; \\  & & Windows 10 education OS \\ \hline PH & Smartphone & Xiaomi Redmi Note 7; \\  & & 4 GB RAM; 64 GB internal storage; \\  & & Android 10 OS \\ \hline HL & MS HoloLens & Microsoft HoloLens 1 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Devices used in the performance evaluation experiments.  
Figure 6: Local network topology used in the performance evaluation experiments.  
mode with 1920 \(\times\) 970 pixels (px) resolution. Full-screen stereoscopic modes were used on PH and HL. The resolution was 1170 \(\times\) 1080 px per eye on PH and 1280 \(\times\) 720 px per eye on HL.  
The same virtual scene was used for all experiments. The scene had a form of a sci-fi-esque hall interior (Figure 7a). The model of the hall had 8550 polygons and was textured by a baked texture. The texture resolution was 2048 \(\times\) 2048 px with 24 bit color depth. The scene was illuminated by a white ambient light, without dynamic shadows. Each user, connected to the scene, was represented by a 3D avatar (Figure 7b). The avatar model had 1370 polygons and did not use textures.