SDDL in wecutil.exe example

Looking here: http://msdn.microsoft.com/en-us/library/windows/desktop/bb870973(v=vs.85).aspx

There is an example of an XML file for configuration settings:

...<LogFile>ForwardedEvents</LogFile><AllowedSourceNonDomainComputers></AllowedSourceNonDomainComputers><AllowedSourceDomainComputers>O:NSG:NSD:(A;;GA;;;DC)(A;;GA;;;NS)</AllowedSourceDomainComputers></Subscription>

It looks like I need to specify a SDDL string for <AllowedSourceDomainComputers>. 

First there are somevalues in the example SDDL string I do not understand. I was not able to find out what NSG: or NSD:mean.

Also I would like to edit the xml file so AllowedSourceDomainComputers would be the "domain controllers" group. Not sure how to do that.