SCCM and WSUS Integration

Our current Architecture is as follows:

We have one Primary site located at our Data center which also has our internet access for the company.  We have multiple branch offices connected via T1s with Secondary Child sites at each.
The primary site server has WSUS installed on it and has the Software Update Point Role installed on it.  Each secondary site has the management point role installed. We are trying to implement software updates via sccm to the remote branch offices in way that will minimize bandwith on our WAN.  Windows updates on the workstations are shut off.


1)      How does the client at the branch offices communicate with WSUS for windows updates?

2)       Will it go thru the management point or will it go directly to the primary site at our data center.

3)      My understanding is that clients will scan the primary site for updates and then report state messages to the management point.  Once the needed updates are determined, will the client get the updates from the primary site or will the primary download the needed updates to the management point that will inturn be accessed by the client?

4)      Is there any advantage to placing the Software Update Point Role on the secondary sites?  I assume that the local clients will communicate with the secondary site directly instead of going back to the primary.  

5)  In this scenario, will clients always go to the SUP at the primary site when performing scans or will it go to the SUP at the secondary site?

6)      How do we force workstations to go to SCCM/WSUS for their windows updates (i.e is a GPO needed to shut it done or does the SCCM client take care of this.