A traffic analysis on the
domain
name
system
(DNS) server of Kumamoto University was carried out with the multivariate statistical analysis. It is found that the total number of DNS packets, D
q , are generated from an electronic mail (E-mail) server, as represented: D
q = m
SMTP N
SMTP + m
POP3 N
POP3 , where N
SMTP and N
POP3 represent the number of the simple mail transfer protocol (SMTP) access and that of the post office protocol version 3 (POP3) access, respectively. The linear coefficients m
SMTP and m
POP3 are calculated to be 8.6 and 1.0. From these results, it is clearly concluded that the DNS access from the E-mail server is mainly driven by the SMTP access to a greater extent than the POP3 access. Also, it is found that m
SMTP is represented, as follows: m
SMTP = 2+4n(1-q), where q is a mail-receiving rate and n is a number of different domain hosts.
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