Adding Customized Services

Services are functions performed by server computers at the request of client computers. You can configure up to 125 custom services.

For example, Web servers serve Web pages, time servers serve time and date information, and game hosts serve data about other players' moves. When a computer on the Internet sends a request for service to a server computer, the requested service is identified by a service or port number. This number appears as the destination port number in the transmitted IP packets. For example, a packet that is sent with destination port number 80 is an HTTP (Web server) request.

The service numbers for many common protocols are defined by the Internet Engineering Task Force (IETF) and published in RFC1700, "Assigned Internet Protocol Numbers." Service numbers for other applications are typically chosen from the range 1024 to 65535 by the authors of the application.

Although the FVS338 already holds a list of many service port numbers, you are not limited to these choices. Use the Services menu to add additional services and applications to the list for use in defining firewall rules. The Services menu shows a list of services that you have defined, as shown in Figure 4-12.

To define a new service, first you must determine which port number or range of numbers is used by the application. This information can usually be determined by contacting the publisher of the application or from user groups of newsgroups. When you have the port number information, you can enter it on the Services screen.

Select Security from the main menu and Services from the submenu. The Services screen will display.

In the Add Custom Service table, enter a descriptive name for the service (this is for your convenience).

Select the Layer 3 Protocol that the service uses as its transport protocol. It can be TCP, UDP or ICMP.

Enter the first TCP or UDP port of the range that the service uses. If the service uses only one port, then the Start Port and the Finish Port will be the same.

Enter the last port of the range that the service uses. If the service only uses a single port number, enter the same number in both fields.

Click Add. The new custom service will be added to the Custom Services Table.

In the Custom Services Table, click the Edit icon adjacent to the service you want to edit. The Edit Service screen will display.

Modify the parameters you wish to change.

Click Reset to cancel the changes and restore the previous settings.

Click Apply to confirm your changes. The modified service will display in the Custom Services Table.