ProSafe VPN Firewall 200 FVX538 Reference Manual
Firewall Protection and Content Filtering 4-21
v1.0, August 2006
Adding Customized Services
Services are functions performed by server computers at the request of clie nt 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 man y common protocols are defined by the Internet Engineering Task
Force (IETF) and published in RFC1700, “Assigned Numbers.” Service numbers for other
applications are typically chosen from the range 1024 to 65535 by the authors of the application.
Although the FVX538 already holds a list of many service port numbers, you are not limited to
these choices. Use the Services screen 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 4-15.
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 newsgr ou ps. When you have the po rt number info rmatio n, yo u
can enter it on the Services screen.
Figure 4-14