In context SSL/TLS, reading up on various sites, I find forward secrecy in DH key exchange being linked to its ephemeral use i.e. DHE. I don't fully understand this link, where does following reasoning break?
If non-ephemeral use (plain DH) would not provide forward secrecy, and ephemerality refers to a new session key being made each time a new session is set up. Then the use of SSL/TLS Session IDs/Session Tickets would make DH-use non-ephemeral.
But how can the compromise of server public/private keys result in the compromise of an earlier established DH session key? I should presume that the nonces which were used are already discarded; and the storage associated to Session IDs/Session Tickets is not necessarily compromised if the server public/private keys are compromised?