Baseline agents can reduce spikes and average load times in monitoring data due to network latency. Baseline agents gather most monitoring samples from specific agents while still taking advantage of monitoring from a worldwide perspective using the GlobalWatch Network.
When configuring baseline agents, choose agents that are geographically closest to the host of your site or application. For example, if your site is hosted in New York, NY, you could set your baseline agents to New York, NY; Newark, NJ; and Scranton, PA. You can then set the additional agents to include other locations. The most up-to-date list of all monitoring agents is available here.
When baseline agents are configured, most samples are taken from the baseline agents; non-baseline agents take samples at a less frequent interval. All alerts are verified by a baseline agent before delivery. Without baseline agents, one sample could be taken from Scranton, and the next from Hong Kong. Because Hong Kong is farther away from New York than Scranton, it may take longer to connect to the site due to network latency, which could create a spike in the data and/or increase average load times, despite the fact that the site itself did not experience any performance issues.
Compare these two Load Time by Period graphs below. These graphs came from two Site Monitoring FullPage Gold services which both monitor the same web site on the same monitoring interval with the same agents. The only difference is the one on the top uses baseline agents, while the one on the bottom does not. Note that the average load time is overall much lower for the service which uses baseline agents and the graph is much smoother.
To use the Baseline Agents feature, your service's monitoring method must be set to sequential (Settings sub-tab > Monitoring Settings option) and you must select a number of baseline agents equal to or greater than your strike count.
The following graphs will use data collected from available baseline agents:
If a graph is using baseline data, (Baseline Agents) will appear in the title of the graph.