I’ve had a few questions come up lately around when Lync 2010 polls Exchange for free/busy information and how/when presence state is updated based on your calendar. I did a bit of digging into it and think I’ve worked a few things out that make the whole situation a bit clearer.
There are two things to consider here. We need to look at how often Lync polls Exchange for the free/busy information, and then how often your calendar state is published to your Lync presence i.e. you change from Available to In a Meeting based on the free/busy data that was retrieved from Exchange.
How is it controlled?
Everything we need to look at here is defined in a Lync Client Policy and there are two parameters that you need to specify interval durations for – either WebServicePollInterval (if you’re using Exchange Server 2007/2010) or MAPIPollInterval (if you’re using Exchange Server 2003) and CalendarStatePublicationInterval. I’ll go into more detail on each of these below.
Lync determines when to change your presence from for example, Available to In a Meeting with this data. This means that if you create an appointment in Outlook in-between when Lync polls Exchange and when Lync applies your calendar state to presence, this won’t be reflected in Lync until the polling interval lapses and Lync retrieve the Free/Busy info from Exchange again.
Retrieving Calendar Data from Exchange
So firstly, we need to look at how calendar data (free/busy information) is retrieved from Exchange Server by Lync.
Exchange Server 2003
If you’re (still) using Exchange Server 2003, Lync will poll the server via a MAPI RPC call for free/busy information. This is controlled in the Lync Client Policy using the parameter MAPIPollInterval.
The default is 30 minutes but this can be changed to anything from 5 minutes to 480 minutes (5 hours). So to set it to 5 minutes, the cmdlet would be Set-CsClientPolicy -MAPIPollInterval 00:05:00.
Exchange Server 2007/2010
Update 28th Jan 2013: Amended to explain that Lync connects to the Exchange Autodiscover service first before being directed to the EWS URL, thanks Marcin Swiatelski. 🙂
For those using Exchange Server 2007 or 2010, Lync will be connecting to your Exchange Autodiscover Service URL and then onto your Web Services URL for free/busy information rather than the local MAPI profile in Outlook.
It builds this Autodiscover URL based on your SIP address, and not by anything you configure in Exchange or from the AD Service Connection Point. So if my SIP address is email@example.com, the two URLs Lync will attempt to connect on will either be:
For Lync to connect to the Exchange Autodiscover service, you need one of these URLs to be accessible.
Typically the autodiscover.sipdomain.com option is the most commonly deployed, as this compliments what is already usually deployed for Outlook 2010 to work.
Once Lync has connected to the Exchange Autodiscover service, it will receive EWS URLs to connect to e.g. https://autodiscover.justin-morris.net/EWS/Exchange.asmx or https://justin-morris.net/EWS/Exchange.asmx
The interval in which Lync connects to EWS to poll for free/busy information is controlled in the Client Policy using the parameter WebServicePollInterval. The default is 30 minutes but this can be changed to anything from 5 minutes to 480 minutes (5 hours). So to set it to 5 minutes, the cmdlet would be Set-CsClientPolicy -WebServicePollInterval 00:05:00.
Publishing Calendar Data to Presence
So now once we’ve retrieved that calendar data from Exchange, Lync needs to actually apply it to your presence, and how often this occurs is controlled by the CalendarStatePublicationInterval parameter in the Lync Client Policy.
Unlike the MAPIPollInterval and WebServicePollInterval parameters, the CalendarStatePublicationInterval parameter must be set in number of seconds.
So to set it to 5 minutes, the cmdlet would be Set-CsClientPolicy -CalendarStatePublicationInterval 300.
Polling and Publication
My understanding from perusing TechNet library articles is that there is a difference between Polling and Publication of calendar information in the Lync client.
I could have interpreted this incorrectly, but I’m pretty sure this is the way calendar information is handled by Lync. If anyone can shed additional light, please let me know in the comments.
TechNet Library References:
Migrating User Settings to Lync Server 2010