Typically DNS6 servers are set up to statically map a given query to a reply or list of replies. In the case of a hostname lookup, an IP address or list of IP addresses will be returned. Generally, the result changes infrequently if at all. It is, however, possible to have a DNS server that returns results based on the output of some algorithm. This allows results to be determined dynamically. In this way the results of DNS lookups may be used the communicate the results of a load balancing algorithm to clients. DNS is a fair choice for this application as the DNS protocol is designed with some measure of redundancy. A domain may have multiple DNS servers and if one fails others may handle requests without the client being notified of any problems.
As an example, suppose that www.slarken.org.au is mirrored between POP X and Y and DNS is being used to distribute traffic between these two POPs as shown in figure 3.
If POP X had been down then the Network C DNS Server would have queried POP Y and returned the IP address of the web server or farm within itself, thus the result would be the same.
If POP Y was down then the query to the route server in POP X would have shown that POP X was the closest POP to the Network C DNS Server and the IP address of the web server or farm in POP X would be returned.
If both POPs were down then there would be no result and the DNS lookup would fail.