Patent ID: 8515079

Claim:
A method comprising: distributing Virtual Private Network (VPN) rekey data from a VPN key server to a plurality of VPN group members using both multicast and unicast rekey messages; transmitting, from the VPN key server, a multicast probe message intended to be received by at least one VPN group member device; wherein the multicast probe message is sent to determine whether a multicast tree is set up and ascertain group member devices that are capable of receiving multicast messages; receiving, at the VPN key server, an acknowledgement message from each VPN group member device that received the multicast probe message and designating, at the VPN key server, each VPN group member device that transmitted the acknowledgment message as a member of a multicast-reachable group; upon determining that a time for a response has elapsed from when the VPN key server transmitted the multicast probe message, designating each VPN group member that the key server did not receive an acknowledgement message from as a member of a unicast-reachable group; transmitting, from the VPN key server, a multicast rekey data message containing the VPN rekey data and intended to be received only by each VPN group member device from which the VPN key server received an acknowledgment message to the multicast probe message; and transmitting, from the VPN key server, a unicast rekey data message containing the VPN rekey data only to each VPN group member device from which the VPN key server did not receive an acknowledgment message to the multicast probe message; wherein the distributing the VPN rekey data is performed by one or more processors.