3.3.5.2.8 Updating Idle Time
For every request received, the server MUST locate the session, using the SessionId in the SMB2 header of the request to do a lookup on the GlobalSessionTable. If a session is found, Session.IdleTime MUST be set to the current time. If the request does not have an SMB2 header following the syntax specified in section 2.2.1 or no session is found, no action regarding the idle time is taken.