Firewalling : Defining your network services : Protocol numbers
Protocol numbers
In IPv4 there is an 8-bit field named Protocol. (In IPv6, this field is named the Next Header field.) This field is used to identify the protocol that the packet contains, which is necessary in order to decode that next layer. Numbers in that field correspond to a known protocol, such as 1 for ICMP, 6 for TCP, and 17 for UDP. When defining a network service, other fields may become available if you have selected the protocol number of a protocol that is understood by FortiADC. These fields enable you to further refine your definition of the service by matching port numbers or other fields located in next higher layer headers.
For example, if you select protocol number 6 (TCP) or 17 (UDP), additional fields appear where you can indicate a subset of port numbers that will define the service.
For a list of network numbers and their associated protocol number, see the IANA protocol number list.