This value specifies which standard, well-known application port, from a supported list including FTP, SMTP, HTTP, RTSP, and H.323, the custom user port should be mapped to for protocol recognition purposes. Administrators set this so the device knows to apply the corresponding application-layer handling to traffic arriving on the nonstandard port defined elsewhere in the same entry. For example, setting this to 80 tells the device to treat traffic on the custom user port the same way it would treat standard HTTP traffic on port 80.