Patent ID: 8274979

Claim:
A method for exchanging digital data between a local area network and a wide area network, comprising: opening a communication session between the local area network and the wide area network; keeping a trace of said session in a session database where said session is associated with a respective session identifier; sending from the local area network to the wide area network at least one data packet having a source port value calculated as the sum of a fixed value and said session identifier; sending from the wide area network to the local area network at least one data packet having a destination port value indicative of the session identifier; determining if said destination port value is higher than said fixed value; when said destination port value is higher than said fixed value: extracting the session identifier from said destination port value by subtracting said fixed value from the destination port value, and using the extracted session identifier for directly accessing said session in the session database; and when said destination port value is lower than said fixed value: discarding the data packet.