You can configure an NSService to specify parameters for matching network traffic such as a port and protocol pairing. You can also use an NSService to allow or block certain types of traffic in firewall rules.
An NSService can be of the following types:
L4 Port Set
An L4 Port Set supports the identification of source ports and destination ports. You can specify individual ports or a range of ports, up to a maximum of 15 ports.
An NSService can also be a group of other NSServices. An NSService that is a group can be of the following types:
Layer 3 and above
You cannot change the type after you create an NSService. Some NSServices are predefined. You cannot modify or delete them.