A communication session for a UE can be restored in the event of serving call session control function (S-CSCF) node unavailability and/or application server (AS) unavailability by storing, prior to IMS unavailability, attribute-value pairs (AVPs) at a home subscriber server (HSS). These AVPs can be used independently by individual IMS nodes to restore a communication session for a UE due to an unavailable IMS node. When a first S-CSCF node becomes unavailable, a proxy CSCF (P-CSCF) node can send a SIP request originating from the UE to a second S-CSCF node. The second S-CSCF node can then send a request to the HSS for an identifier of an AS associated with the UE. Upon receipt of the AS identifier (e.g., an active AS name AVP) from the HSS, the second S-CSCF node can send the SIP request to the AS in order to restore the communication session for the UE.