C H A P T E R 2

Intel® NetStructure™ 7190 Multi-Site Traffic Director User Guide

Site

Balancing

Methods

The 7190 supports six site-balancing methods or algorithms. The operator chooses the method most appropriate to the deployment to optimize traffic volume, priority, resource availability, and the overall desired outcome.

Weighted Algorithms

Weighted Round Robin - Two differences distinguish this method from traditional, or round robin, DNS. First, the 7190 is aware of the status of the sites it balances thus, unlike legacy Round Robin, it does not indiscriminately send requests to servers that have gone down or are otherwise unable to fulfill requests. Second, weighted round robin allows the operator to skew the loading among available site services on the basis of an assigned “weight.” (Weight takes into account differences in capabilities of site services.) Weighting allows the operator to adjust loading on a percentage basis. For example, Site A is assigned a weight of 1, Site B, 2, and Site C, 7. Thus, Site A receives 10% of the traffic, Site B, 20% and Site C, 70%. This method can ensure the most efficient use of those sites with greater “horsepower,” while preventing the overtaxing of less powerful ones.

Weighted Random - The Weighted Random method is similar to Weighted Round Robin with the exception that requests are not fulfilled serially. IP addresses are resolved in a random fashion. The weighting is accomplished as above. The benefit of this algorithm is that it is more effective at normalizing, or leveling, load.

Metric Algorithms

Using DNS to balance multiple sites is more effective when the referrals are based upon knowledge of the actual loads on the servers. In addition, balancing effectiveness noticeably increased when back- to-back referrals to the same site were not made even if metrics indicated one site service was the best both times. The 7190 metric algorithms reflect both of those findings.

These balancing algorithms are not available for sites that do not have Intel load balancers:

Response Time - The Response Time method directs requests to the site that has the fastest aggregate (i.e., across all servers) response time for the requested service. Likely users of this method are enterprises that have identified the efficient

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Intel 7190 manual Site Balancing Methods, Weighted Algorithms, Metric Algorithms