Update Mgmt Plug-in vs. Catalog Management

Hey,

I'm a little bit confused what's the real difference in using the Update Management plug-in vs. importing a catalog to the Catalog Management to update the servers firmware. I'm especially interested in the data flow; from where will the (offline) iDRAC get the update files.

Given scenario:
DELL.com <--http/s-- DELL Repository Manager <--CIFS-- DELL OME (offline) <---- iDRAC servers

- DELL Repository Manager: has internet access, hosts the CIFS share
- DELL OME: has no internet access, can access DRM CIFS share
- iDRAC: has no internet access, can access OME (and needs access to CIFS on DRM?)

Case 1 - DELL Repository Manager & Update Management plug-in
In this scenario the Repository Manager (DRM) downloads catalog and payload from dell.com and stores it in a CIFS share. The Update Management plug-in (OME) connects to the CIFS share and downloads catalog and payload locally to the OME server. When an iDRAC is updated, it gets all the necessary data from the OME server; correct?

Case 2 - DELL Repository Manager & Catalog Management
The Repository Manager (DRM) holds catalog and payload in a CIFS share. In the OME Catalog Management I'm adding the catalog.xml from that CIFS share. If I'm now going to update an iDRAC server, where does it get its payload files from? Does the iDRAC connect directly to the DRM CIFS share? Does the OME download the files from the DRM and the iDRAC loads it from the OME?

It would be nice to get a more detailed overview and/or port diagramm for the given cases. Thanks very much!