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Active, or passive monitoring, that is the question —

How to make your user experience / SLA awake: active and passive monitoring combined

Service Level Management is  fundamental to ensure service quality at both the technical and business level. In order to be effective, not only internal services  but also third party ones (ex. ads) need to be monitored.

SLA monitoring should be carried out with both active and passive methods because they focus on two distinctive features:

  • Active monitoring, also referred to as synthetic monitoring, performs regular, scripted checks that simulate end-user behavior in controlled and predictable conditions

  • Passive monitoring concentrates on real end-user activities by “watching at” what they are doing right now

to be or not to be

Active (aka synthetic) Monitoring

What are the distinctive features of active monitoring and why is it useful ?

Synthetic script-based approach is the only feasible method for availability monitoring because:

  • it occurs from outside the datacenter and so it enables for monitoring of timing and errors specific to external web components not hosted locally

  • it determines if the site (or specific page) is up or down

  • it verifies the site availability when there are no end users hitting that particular page

  • it can test various protocols (not only HTTP/S) like Flash, Silverlight, Citrix ICA, FTP, etc.

  • it is able to execute scripts from specific locations and so it can determine region-specific issues

  • it is essential in order to establish a performance baseline before a new application release deployment

Actually, there are some drawbacks too:

  • a script tests the same navigational path over and over again

  • the test is not “real”: you can’t buy something every five minutes on a real web site

  • periodic sampling does not provide a good indication of what real users are experiencing

  • a script cannot test odd human combinations

Passive (aka sniffing) Monitoring

What are the distinctive features of passive monitoring and why is it useful ?

Passive “sniffing” approach is the only feasible way to look at real users conditions:

  • it looks at the traffic generated by real users of the website

  • it enables monitoring of real transactions, such as bank transfers, purchases, and so on

  • it measures all aspects of your users’ experiences: user location, browser, ISP, device, etc.

  • it detects all errors that can occur and is able to take screenshots of these situations

Actually, there are some drawbacks in this case too:

  • the data collected is limited to the traffic on the network the router is attached to

  • It requires real users traffic; if there are no users on the site it cannot collect any data

  • It offers no ability to monitor issues that occur outside of the network, such as DNS problems, network issues, and firewall and router outages

The combination

The combination of active and passive monitoring provides a more comprehensive view of performance, availability and end user experience. In addition, for companies that outsource their infrastructure, active monitoring offers a way to validate the SLAs provided by the outsourcer.

Using an approach that combines both passive and active monitoring methods offers the highest degree of quality assurance because issues can be detected before they occur or in near real time.

For additional information, pls contact me.

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