D-Link DWR-923 User Manual page 50

Advanced NAT  Special Applications
While common services use known TCP/UDP ports, many custom or
uncommon applications require traffic to be sent through the firewall.
This section introduces the custom services of the DWR-923.
Service Name: Name of the service for identification and management
purposes.
Protocol: The layer 4 protocol that the service uses: TCP, UDP.
Start Port: The start of the port range for the custom service.
End port: The end of the port range for the custom service.
Click Add to add a special application, or select an item and click Edit to
modify or click Delete to delete the selected item.
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