Patent ID: 7143137

Claim:
A method for enhanced security when communicating over a network between a client computer behind a network address translation (NAT) configured gateway computer, and a remote computer, in response to the client computer making a first request for an IP address from the gateway computer, the method comprising: providing a public address from the gateway computer to the client computer, the public address being one of a gateway computer public address and a pool of gateway computer public addresses and being associated with a medium access control address for the client computer; participating in a security association negotiation with the remote computer to obtain a security parameter index (SPI) from the remote computer provided to the gateway computer; obtaining an initiator indicator comprising a negotiation status bit associated with the security association negotiation from the client computer; and using the SPI as an indicator to record a local address for the client computer in association with a destination address for the remote computer, the local address and the destination address being obtained from the security association negotiation and recorded in a mapping table accessible by the gateway computer in association with the medium access control address, recording the initiator indicator in the mapping table in association with the local address, the medium access control address, a time stamp, and a security protocol type identifier in response to the existence of at least one type of security protocol header, to establish a unique secure communication between the client and the remote computer, the SPI thereafter being used to direct an incoming data packet from the remote computer to the client computer.