An introduction to Exchange 2010 ActiveSync throttling

There are several benefits to having a centralized hub for client connections to Exchange Server. However, Exchange Server 2010 can put the client

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access server (CAS) at risk for overload. Throttling policies regulate connectivity to the CAS. Because ActiveSync uses the CAS to connect to Exchange, it’s useful to have a throttling policy in place to regulate connectivity. Here are some throttling policies specifically for ActiveSync.

Throttling policies can control ActiveSync behavior in a variety of ways. EASMaxConcurrency is one of the most useful ActiveSync throttling policy settings. The setting limits the total number of concurrent ActiveSync connections that a user can have at one time. Two other throttling policies dedicated to ActiveSync are EASMaxDevices and EASMaxDeviceDeletesPerMonth.

There is nothing stopping a user from using ActiveSync to receive mail on two or more mobile devices. The EASMaxDevices policy sets limits on the total number of active device partnerships a user can have and limits the number of devices a user can connect to ActiveSync at one time.

When a user connects his mobile device to Exchange through ActiveSync, it forms a device partnership. Users can view and manage device partnerships through Outlook Web App (OWA). The EASMaxDeviceDeletesPerMonth setting controls how many of a user’s device partnerships can be deleted each month. This throttling policy setting is useful when each user has only one device.

The the EASMaxDeviceDeletesPerMonth policy setting also acts as a safeguard against curious users who may explore different options in the Exchange Control Panel. And those users might inadvertently delete their ActiveSync partnerships while in the process. Set this policy to prevent users from damaging the ActiveSync link.

Checking ActiveSync throttling efficiency 
Once you’ve put these ActiveSync throttling policy settings into place, it’s important to monitor changes. Microsoft provides several performance monitoring counters for this; two of most useful are MSExchange ActiveSync\Current Requests and MSExchange ActiveSync\Provision Commands/sec.

The Current Requests counter displays the current number of ActiveSync requests, giving you an idea for how heavily users rely on ActiveSync. The Provision Commands/Sec counter displays how many requests to provision new mobile devices are sent to the CAS each second.

ABOUT THE AUTHOR
Brien M. Posey, MCSE, is a seven-time Microsoft MVP for his work with Windows 2000 Server, Exchange Server and IIS. He has served as CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. For more information visit www.brienposey.com.

This was first published in March 2011

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