Well Known Service resource.
TypeValue = 11
ClassValue = IN::ClassValue
The host these services run on.
IP protocol number for these services.
A bit map of enabled services on this host.
If protocol is 6 (TCP) then the 26th bit corresponds to the SMTP service (port 25). If this bit is set, then an SMTP server should be listening on TCP port 25; if zero, SMTP service is not supported.