DFS and DFSR failover

Hi, 

I'm looking at setting up DFS Namespace and DFSR for some remote branches and just wanted to get some expert advice:

I understand that if a local server at a branch office fails then the users will be auto-redirected to another server (according to the sites configuration). But when happens is a network link fails? I know DFSR will fail, but will the namespace still stay at the local server? In that case what happens when the link comes backup?

secondly, am I right in thinking that there is no awareness in the Namespace that would stop 2 users trying to open/save the same file from 2 different branch offices. If that was to happen how would DFSR deal with the 2 modified files. 

Thanks.