1.3 Overview

The DirectPlay 8 Protocol: NAT Locator consists of three separate packet types: path tests, Network Address Translation (NAT) resolver queries, and NAT resolver responses. These optional messages are used to modify behavior of the DirectPlay 8 Core and Service Providers Protocol [MC-DPL8CS] connection process so as to increase support for network environments that involve NAT. They are not required for operation of the DirectPlay 8 Core and Service Providers Protocol.

Path tests are packets used to augment the DirectPlay 8 Protocol: Core and Service Providers connection process. While an existing participant is initiating a connection to a new player in response to a DN_MSG_INTERNAL_INSTRUCT_CONNECT message from the host, it can configure itself to accept PATH_TEST messages from the new player. Similarly, the new player can begin to periodically send PATH_TEST messages to the existing players from which it expects to receive connection attempts. These PATH_TEST messages are used to create port mappings in NAT or firewall devices that would otherwise prevent the DirectPlay 8 Protocol: Core and Service Providers connection from succeeding.

NAT resolver queries and responses are part of an out-of-band mechanism to enable DirectPlay 8 Protocol: Core and Service Providers hosts to acquire additional addressing information that they can provide to potential clients to improve connectivity in specific, limited NAT scenarios. They enable hosts to create port mappings in NAT or firewall devices and identify the resulting public address and port. This public address and port can then be advertised instead of the local, private address and port that hosts normally would advertise.