What happens to DHCP sessions on client devices when the DHCP server breaks down and comes online after an interval?

Scenario: I use DHCP to authenticate and provide specific services to my device.

  1. Everything is working well, my client device has a valid IP address 192.168.0.2 and a QoS service assigned by the DHCP server.
  2. My DHCP server breaks down, device still holds on to the IP address 192.168.0.2 because of the available lease time and is able to communicate with other devices in the network.

I would like to know what exactly happens when the DHCP server comes online again. Will the DHCP server know about the DHCP state held by my client device along with the granted QoS service? Or will the device have to be authenticated again in order to avail the QoS service?

Any help or information on the above would be highly appreciated.