version field
Many protocol headers have a version field in which the currently used version of the corresponding protocol is entered.
The version field is usually the first data field in the header. It is a 4 or 8 bit long data field in which the used version of a protocol is entered. The version field can be found in different IP protocols. To ensure proper operation of the devices, all devices must work with the same IP version. Devices working with other versions discard the IP packets.
In the IP header, the version field comprises four bits and identifies the version of the IP protocol in use. For the currently used version IPv4 a 4 must be entered in the version field, for the version IPv6 a 6; the versions 1 to 3 are no longer used. For the identification of the protocol version there are the designations: IP Next Generation( IPnG), IPv4 and IPv6.