# Evaluation of Modern Internet Transport Protocols over GEO Satellite Links
## 6 Results and Discussion
### The Effect of the Web Page Structure  
The perceived user-level performance of downloading multi-object web pages is affected by the number of embedded objects, their sizes and how they are arranged in the web page. We assess this effect using the First Contentful Paint (FCP) and the Largest Contentful Paint (LCP), defined in Table 5, in addition to the average PLT. The two web page structures considered here are the uniform multi-object page, with equal objects' sizes, and the triangular multi-object page, where the objects are arranged in increasing-then-decreasing order as described in the previous section. The test used HTTP/2 and HTTP/3 over TCP, and QUIC while fixing the congestion control algorithm as BBR because it can fully utilize the channel.  
Figure 10 shows the average First Contentful Paint (FCP) of downloading multi-object web pages over HTTP/2 and HTTP/3 in the satellite link. Here, we observe that HTTP/2 needs more time to get the first object from the server compared to HTTP/3. The reason is that HTTP/2 uses TCP which requires a three-way handshake for connection setup and another handshake for TLS security. HTTP/3, on the other hand, uses QUIC which requires only one RTT (1-RTT handshake) for the combined connection setup with TLS security. In addition, all HTTP protocols need at least two RTTs to complete a page request: one RTT to request the main web page (index page) and another RTT to request the first object within the page after the browser parses the main page as illustrated in Figure 11. The triangular multi-object web page structure yields smaller FCP than the uniform in both HTTP/2 and HTTP/3. This is because the first object in the triangular structure is the smallest among the eight objects embedded in the web page. So, it will finish earlier than the first object in the uniform web page structure.  
Next, we look at the second user-experience metric which is the time from the web request until the most significant (largest) object within the web page is loaded successfully. The average Largest Contentful Paint (LCP) of multi-object web pages in the satellite link is shown in Figure 12. Here, HTTP/3 also outperforms HTTP/2 for the same reasons described earlier. However, the results clearly show the effect of the object size distribution and order within the web page itself. The triangular web page has smaller LCP than the uniform web page in both HTTP/2 and HTTP/3. Because the largest object in the triangular structure is located in the middle of the web page, it loads faster when parallel streams are used as in HTTP/2 and HTTP/3. This has a clear improvement on the perceived visual rendering of the web page as seen by the user.  
Figure 11: Connection setup, security and request/response timeline in HTTP/2 and HTTP/3.  
Figure 12: Largest Contentful Paint (LCP) of multi-object web page in a satellite link.  
Finally, the average page load time (PLT) of downloading uniform and triangular web pages is shown in Figure 13. Clearly, the object distribution within the web page does not affect the PLT because it is determined by the total time needed to fetch all objects in the page successfully regardless of the size or location of each object.