Services and TCP ports
There are a number of different services and protocols in use on the Internet. The most commonly known is HTTP which is used by web servers to transmit requests and responses for unencrypted web pages. These services are set up to listen for requests on a numbered port. These services and protocols can use any port from 1 to 65,535. To keep things simple for everyone a large number of the more commonly used services started using a standardized list of ports. For instance, though it is not required, by default, most web servers listen for HTTP requests on port 80 and by default, web browsers will send HTTP traffic to port 80. If you wish to use another port such as 8080 you would put “:8080” at the end of the URL to indicate that you want the browser to use 8080 instead of the default port.
Example
Default URL for HTTP traffic when the web server is listening on the standard HTTP port: http://fortinet.com
URL to the same address when the web server is listening for HTTP traffic on port 8080 http://fortinet.com:8080
Services represent typical traffic types and application packets that pass through the FortiGate unit. Firewall services define one or more protocols and port numbers associated with each service. Security policies use service definitions to match session types. You can organize related services into service groups to simplify your security policy list.
Many well-known traffic types have been predefined on the FortiGate unit. If there is a service that does not appear on the list you can create a service or edit an existing one. You need to know the ports, IP addresses or protocols of that particular service or application uses, to create a service.
Best Practices
While you can edit a predefined service it is best to leave those ones alone and create a new service and name it something similar such as the same service name with a descriptive identifier appended.
Based on the previous example, instead of the name “HTTP” you could name the service “HTTP8080” or use the application that is using that port, “HTTP-Application”.