Intel 7190 manual Intelligent, Traditional

C H A P T E R 2 Intel® NetStructure™ 7190 Multi-Site Traffic Director User Guide

“Intelligent”

DNS

Traditional

DNS

The 7190 leverages the DNS architecture and protocol as the basis for its site balancing operations. Based on the information gathered from all sites, the 7190 returns the address of the site that best meets the criteria for fulfilling the request.

Traditional, or Round Robin, Domain Name Service (DNS) is a rudimentary means of server load balancing. Under this method, a single hostname is mapped to a list of multiple server IP addresses. When the DNS server resolves a request for that hostname, it returns the entire list to the requestor, then sorts it (the first name drops to the end of the list). Upon receiving the list, the client requestor typically uses the first address. The next requestor of the hostname receives the resorted list, and again most likely uses the current first name. The list is resorted again, so that each sequential request sees a different “first choice” than the previous one. The chief benefit of Round Robin DNS is that it allows requests to be distributed to multiple hosts and, in theory, provides a layer of redundancy. On the negative side, the DNS server has no knowledge of the status of the sites to which it sends requests. Receiving sites may be heavily loaded or dead, thus the potential is high for unacceptably slow replies error messages to clients, which is out of the site operator’s control.

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