Measurement Analysis of Co-occurrence Degree of Web Objects

As a technique to reduce the web response time, HTTP/2 and HTTP/3 have been standardized. However, parallel download in these techniques is possible only for web objects which are provided from the identical object server, so many web objects need to be downloaded from a small number of object servers to improve the effect of HTTP/2 and HTTP/3. To deliver web objects, CDNs delivering objects from cache servers located near requesting users have been widely used. Hence, if we define the co-occurrence degree as the number of webpages in which an object set is included, it is desirable to replace cached objects so that object sets with high co-occurrence degree are remained in the cache. However, the effectiveness of replacing objects based on the co-occurrence degree strongly depends on how the co-occurrence phenomenon of objects appears in the actual webpages. Therefore, in this paper, to clarify the potential of cache replacement based on the co-occurrence degree, we investigate how much the co-occurrence phenomena of objects are observed in actual webpages by measuring the most popular 7,604 webpages. We confirm that the distribution of co-occurrence degree of objects obeys a power law, and the co-occurrence degrees of about 0.01% two-objects sets and 0.001% three-object sets exceed 500. Hence, we confirm the potential of cache replacement based on the co-occurrence degree of objects.