Tidbits on CUPS Integration with Exchange

William Bell
Vice President, Solutions and Products

 Before laying out some of the gotchas, the basic integration requirements overview is provided here:

1. You need to have a user configured in AD for the CUPS server.  This is a service account for authenticating to AD and opening the Exchange calendar for the CUPS user.

2. This CUPS user needs to be configured in Exchange, have a valid mailbox, and part of the Exchange View Only Administrators group (that’s how it can open the user’s Exchange calendar).

3. The CUPS server actually uses WebDav to do its business.  Cisco is working on moving away from this API and using EWS, but this is not committed on the roadmap.  The move is a necessary one as Microsoft is pushing people away from WebDav.

4. CUPS uses OWA to connect to the Exchange services.  This should be running on the client access servers (CAS) in Exchange 2007 or the Exchange Front End servers in Exchange 2000/2003.

Important note: CUPS does not support forms based authentication (FBA) on Exchange 2007 (only version tested) (I will test 2003 in the lab later)

5. Since CUPS is using OWA, HTTPs is required, and CUPS has no way of dynamically accepting/storing certificates, IOW you have to upload the certificates to the CUPS server

So, some interesting tidbits:

CUPS 7.0 seems to only care about the root certificate for the Presence Engine trust.  At one of our customers I uploaded the root certificate and then the server/application certificate from the OWA server.  After refreshing services, the OWA server certificate disappears.

This behavior is different then loading the certificate for a local application service.  For instance, if you wanted to use a 3rd party certificate for the Tomcat service (web server) you must load the root certificate first and then load the application certificate.  Makes sense when you think about it.

Another interesting note is that when configuring the Presence gateway for the OWA server.  The gateway host should be the Fully Qualified Domain Name (FQDN).  Further, the FQDN must either be the CN of the certs Subject field or X.509 subject alternative name field of the OWA server certificate (the one you don’t need to install).

To determine the CN (or alternative name) use a web browser to open a SSL session to the OWA server.  Once connected to the server, use your browser to view the certificate properties.  This is also a good way to find the root authority if you don’t know it.

The final tidbit for today is related to DNS domain names and AD forst domains.  For CUPS, when you configure a user ID field in the Exchange presence gateway, it will attempt to authenticate with that user name as configured. So, cups is simply “cups”. However,  Exchange OWA wants some indication of the domain.  So, you have to specify the domain you are authenticating against in the logon request.  Further, CUPS won’t take the pre-2000 convention (e.g. netcraftsmencups). So, you have to use the format: cups@netcraftsmen.net (if you were one of those companies that configured your AD tree to use the SAME domain as your public DNS record, another can of worms). 

That is all for now.  There is plenty of info on Exchange and CUPS integration but that will be for another day.

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