The nameserver (bind.cc.nd.edu) looks in its database to see if it knows who foyt.central.sun.com is and how to get there.
If the nameserver has an entry for the foyt.central.sun.com machine skip to DNS-resolved .
If the nameserver does not have an address for the foyt machine, it sends out an DNS request to it’s master nameserver (.edu) saying “Hi, I’m bind.cc.nd.edu, I live at 188.8.131.52, my MAC address is 08:00:20:ff:ee:dd. Who is foyt.central.sun.com and how do I get there?”
This starts an iterative process of nameservice lookups...
Darwin sends an IP packet to foyt.central.sun.com at IP address 184.108.40.206 saying “Hi, I’m darwin.cc.nd.edu, I live at 220.127.116.11 and my MAC address is 08:00:20:00:4e:3f. I’d like to contact your finger server (port 79) with the information contained in the data segment of this packet”
Foyt.central.sun.com receives the packet, decodes the protocol information and determines that it is for the /usr/etc/in.fingerd program.
Foyt forwards the packet to it’s finger daemon on port 79.
The finger server on foyt looks up the information requested by the user on Darwin, and sends a packet out on the net saying “Hi there darwin.cc.nd.edu, I am foyt.central.sun.com. I live at 18.104.22.168, my MAC address is 11:22:33:44:55:66, here is the information you requested.
Darwin receives the information from foyt, thanks the foyt machine, and sends the data to the user’s terminal.
Darwin adds the Foyt machine to it’s named cache.
The user finds out their friend wasn’t logged in, goes home and drinks beer (or whatever users do when not logged in to a system).
name - is the name of the domain object this record refers to. This can be a hostname, or an entire domain. Name is relative to the current domain unless it ends in a “ . ” (dot). If the name is blank, this record applies to the domain object from the last name command.
ttl - Time-to-live defines the length of time (in seconds) that the resource record should be kept in cache. Usually blank so the default (in an SOA record) is used.
class - defines this to be an Internet DNS record. Other record types are possible but not used by DNS.