You notice that the Active Directory Federation Services (AD FS) server is experiencing larger than expected loads. These loads are more than 40 percent greater than expected. When you examine the traffic, most of the load is from recurring authentication requests from Microsoft Lync 2010. Lync 2010 is continually requesting Office 365 authentication system tokens. This may be because of failed requests to Exchange Web Services (EWS). Each EWS request that Lync 2010 retries to send requires a new Office 365 authentication system token, and the Office 365 authentication system requests are causing the increase in authentication traffic to the AD FS server.
To fix the cause, identify what is causing the failed (and therefore retried) calls to EWS. For example, load balancer changes that are not persisting cookies. The update in this KB will cause the Lync 2010 client to cache the Office 365 authentication system token and therefore not continually make requests to AD FS and the Office 365 authentication system back-end. However, the retried requests to EWS would continue.
To resolve this problem, install either of the following cumulative updates:
2670498 Description of the cumulative update for Lync 2010: January 2012
2670326 Description of the cumulative update for Lync 2010: February 2012
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.