Dynamic RTT load balancing makes use of direct measurements from each “site” NetScaler to the remote LDNS IP address to find the site closest to the user’s LDNS. As a result of this, RTT can reduce maintenance on the configurations versus the static table method of proximity, and in theory provide more accurate locations for users. To measure the performance, three monitors are activated on the remote IP address in the following order:

• First a ping of the IP address (LDNS-PING), if that fails; then

• A DNS TCP probe (the syn-ack response time is used as the round trip time) (LDNS-TCP), and if that also fails;

• A DNS UDP query for the domain “.” (LDNS-DNS)