ADFS working when one Domain Controllers is down

Hi folks,

ADFS with SharePoint/O365 use, two Domain Controllers, when one domain controller is down SharePoint or O365 does not work anymore.
What is the process how ADFS uses Domain Controller and what is the time frame when ADFS server, change connection to the working Domain Controller.

I found that the lifetime of a default security token for a claims-based authentication deployment using AD FS 2.0 is 60 minutes. If user restart IE session does
new session start with working domain controller? how can I manually say to ADFS server, please check topology, one Domain Controller is down?

Br,
Ari