## 4 Measurement Results
### Daytime View  
In the following, we investigate if and to what extent the daytime has an effect on the performance of a request of the two connections types, _i.e._, via the Tor network and the direct connection. In Figure 8, the average core latency of all nine nodes for every hour of a day for both connection types (Tor and direct) is displayed. (We tested for the node in Germany that the average has a similar progression like the median, the 25% and the 75% quantile.) The other metrics show very similar results, therefore we did not visualize them. In order to allow for a better comparability and to take the time shift of the geographical location of the nodes into account, we represented the timestamps for every request in GMT. Furthermore, we highlighted the local time at noon by means of a vertical dotted line in Figure 8.  
Figure 8: GMT Daytime Comparison (Core Latency; +: Direct, x: via Tor). (**a**) Australia; (**b**) Taiwan; (**c**) Russia; (**d**) Germany; (**e**) UK; (**f**) Brazil; (**g**) Canada; (**h**) USA (East Coast); (**i**) USA (West Coast).  
Our results indicate that the latency of direct connections is nearly constant over time of the day on most nodes. Especially Australia, Russia, UK, Brazil and USA (West Coast) show very little differences regarding the performance during different hours of a day. Only the nodes in Germany and Taiwan have a noticeable peak after noon (local time). The node in Canada shows a peak at 10 AM local time, and in the USA at 9 AM local time. The other metric, download throughput, confirms these results. We argue that this stability of the performance of the direct connection is provided by the mature backbone infrastructure of the Internet which has enough capacity available for web access even during Internet \"prime-time\" when approximately 25% of all traffic is generated [50] and Internet traffic is about 72% higher than during an average hour [51].  
Comparing both connection types, _i.e._, the direct connection and through Tor, we can state that the daytime has a stronger influence on the Tor network than it has on the direct connection. This finding is consistent for all metrics. The Tor connection does not show a stable performance and seems to be affected by daytime. There does not seem to exist an exact common pattern explaining the performance variation of the Tor connection (cf. Figure 8). However, in general the overall performance appears to be decreasing during GMT evening hours independently of the location of the PlanetLab node.  
Contrasting this with the results for direct connections, we argue that this effect is more dependent on the performance of Tor than on the geographical location of the client nodes. Tor nodes are usually selected worldwide in a random fashion, without preference for nodes which are physically close [52]. Although it is not part of the Tor route selection process, traffic is often routed through nodes located in different countries, and every node adds some latency. Since Tor nodes are not evenly distributed around the globe, Tor speed could correlate with the current local daytime of the majority of nodes in use (such as UK and Germany). This leads us to the conclusion that the diurnal behavior of Tor latency is in general more influenced by global factors than by local factors at the client.  
Figure 8: _Cont._