GSLB Domains Test

GSLB (Global Server Load Balancing) is a Domain Name Server (DNS)-based solution that load balances services between geographically distributed locations. GSLB relies on DNS for directing client requests. GSLB enables the NetScaler appliance to make intelligent network traffic direction decisions based on the configured method. GSLB responds to DNS requests for a domain name with an IP address of a member service. Which service IP is returned is dependent on the load-balancing algorithm used - for example least connection, simple round robin or more commonly used, proximity to the client (or the clients local DNS to be precise).

To understand how efficiently a NetScaler appliance configured with GSLB performs load-balancing, you first need to understand the DNS request load on the appliance and the most-requested domain names. The GSLB Domains test provides this information. This test tracks the DNS requests received by the NetScaler appliance, automatically discovers the domain names that are requested, and reports the number of requests received for each domain name. Besides enabling you to instantly capture a sudden or a steady increase in load, this test also helps you point to those domains that are requested the maximum. This test can also provide provide early pointers to what could be a potential request processing bottleneck on the NetScaler appliance. 

Target of the test : A NetScaler VPX/MPX

Agent deploying the test : A remote agent

Outputs of the test : One set of results for each domain that is requested for.

Configurable parameters for the test
Parameter Description

Test Period

How often should the test be executed.

Host

The IP address of the host for which the test is being configured.

NetScaler Username and NetScaler Password

To monitor a NetScaler device, the eG agent should be configured with the credentials of a user with read-only privileges to the target NetScaler device. Specify the credentials of such a user in the NetScaler Username and NetScaler Password text boxes.

SSL

The eG agent collects performance metrics by invoking NITRO (NetScaler Interface Through Restful interfaces and Objects) APIs on the target NetScaler device. Typically, the NITRO APIs can be invoked through the HTTP or the HTTPS mode. By default, the eG agent invokes the NITRO APIs using the HTTPS mode. This is why, the SSL flag is set to Yes by default. If the target NetScaler device is not SSL-enabled, then the NITRO APIs can be accessed through the HTTP mode only. In this case, set the SSL flag to No.

Measurements made by the test
Measurement Description Measurement Unit Interpretation

DNS queries received

Indicates the number of DNS requests received for this domain name during the last measurement period.

Number

A high value for this measure could indicate an increase in the load on the NetScaler appliance. Under such circumstances, you can quickly compare the value of this measure across domains to identify the domain that has received the maximum requests. You may want to observe the traffic to this domain for a while to know whether there was a consistent increase in the load or was it just a sudden occurrence.  A consistent rise in the number of requests could indicate a potential processing bottleneck.