Method and protocol for synchronized transfer-window based firewall traversal

DETAILED DESCRIPTION In accordance with a preferred embodiment of the present invention, some of the problems associated with using firewalls are overcome.
A protocol and method for synchronized transfer-window based firewall traversal is presented.
The firewall traversal protocol and method are used by a first network device on a first network inside a firewall to coordinate a connection with a second network device on a second network outside the firewall.
Secure firewall traversal information is sent from inside the firewall to outside the firewall.
In firewall traversals known in the art, a second network device on a second network outside a firewall typically coordinates a connection with the first network device on the first network inside a firewall.
A preferred embodiment of the present invention coordinates a connection through a firewall from inside the firewall.
The firewall traversal protocol includes an open-transfer window message, an open-transfer window acknowledgment message, a close-transfer-window message and a close-transfer window acknowledgment message.
However, the firewall traversal protocol can also include more or fewer messages and preferred embodiment of the present invention is not limited to four firewall traversal protocol messages.
The open transfer-window message opens a "virtual" data transfer-window in a firewall.
The open transfer-window message includes secure firewall traversal information such as: a network address of a network device within a firewall (e.
g.
, an IP address of a specific network access card) to use for data transfer; a starting firewall traversal sequence number to use to begin a data transfer; Security Parameters Index ("SPI") or other encryption indicator; transfer rate information to ensure the network device is not overloaded during the data transfer; or other desired information.
The open transfer-window acknowledgment message includes firewall traversal information from the open transfer-window message and acknowledges the open transfer-window message, thereby providing synchronized firewall traversal