In communication protocols, the user data is transferred in the Payload data field. Depending on the protocol concept, the data field provided for this purpose in the protocol header can have a fixed or a variable size. To determine the length of the payload, some transport protocols have the Payload Length( PL) data field in which the payload length is entered.
For example, the Payload Length (PL) data field in the IPv6 protocol is a 16-bit long data field. It identifies the payload length, which is entered in bytes. The data field includes the extension header. The 16-bit data scope of the payload length means that payload data of up to 65,535 bytes is possible with the IPv6 protocol. For more extensive payload data, the payload length field can be set to 0, and with the optional Jumbo Payload, larger payload values can be displayed in the Next header field via the Extension Header in the Hop-by-Hop option.