Excel Services external data sources - Kerberos or SSO required??
 

Hello,
I'm seeing a lot of confusion on newsgroups regarding this topic.

I, like many others, attempted to publish an Excel Services workbook to
Sharepoint 2007. The workbook had a pivot table which goes against Analysis
Services.

The excel workbook launches fine (in the Excel Web Part), but when I try to
drill down in the pivot table (which requires a data refresh), I get the
standard:

Unable to retrieve external data for the following connections:
The data sources may be unreachable, may not be responding, or may have
denied you access.
Verify that data refresh is enabled for the trusted file location and that
the workbook data authentication is correctly set.

We have a distributed deployment (Excel box != Sharepoint box != client
box). I've seen several discussion threads that claim that in a best
practices distributed deployment, the only way for Excel Services to be able
to authenticate against the remote SQL Server is to switch to Kerberos or SSO
authentication.

Is this true? Our web team is freaking out, so I need confirmation is this
is a real requirement before I slam my fist down ;)

Thanks,
Alex