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Analysis results

We conducted our measurement study for about three months, and nineteen Web sites participated, as described in Table 2. We classify these sites into two categories: commercial (sites 1-3) and educational (sites 4-19). As we show in Section 3.1, the client and local DNS associations visiting these two sites have very different characteristics. For ease of discussion, we use LDNS to represent a local DNS server. A total of 4,253,157 unique client and LDNS associations were collected. Table 3 presents the statistics of the DNS server and the redirector log for all sites.


Table 2: Participating sites in the study
Site Type # of 1-pixel Duration
image hits
1 att.com 20,816,927 2 months
2,3 Personal pages
(commercial domain) 1,743 3 months
4 Research lab 212,814 3 months
5-7 University sites 4,367,076 3 months
8-19 Personal pages
(university domain) 26,563 3 months


Table 3: DNS and HTTP log statistics for all sites
Type Count
Client-LDNS associations 4,253,157
HTTP requests 25,425,123
Unique client IPs 3,234,449
Unique LDNS IPs 157,633
Client-LDNS associations where
client and LDNS have the same IP address 56,086

To study the proximity between the client and its local DNS server, we use the following four metrics.

AS clustering, network clustering, and traceroute divergence are topology-oriented metrics, while round-trip time correlation is a performance-oriented metric. AS and network clustering are passive, requiring no active probing. The other metrics are highly dependent on the probe locations. To obtain an exhaustive evaluation of proximity, we include all four metrics in our study.



Subsections
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Next: AS and network clustering Up: A Precise and Efficient Previous: Measurement impact