Well Known Service resource.

Methods
N
Constants
TypeValue = 11
 
ClassValue = IN::ClassValue
 
Attributes
[R] address

The host these services run on.
[R] bitmap

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.
[R] protocol

IP protocol number for these services.
Class Public methods
new(address, protocol, bitmap)

Source: show | on GitHub 

# File lib/resolv.rb, line 2025
def initialize(address, protocol, bitmap)
  @address = IPv4.create(address)
  @protocol = protocol
  @bitmap = bitmap
end