Siemens Mobility GmbH The use of IPv4 options on the public internet is limited due to the fact that many currently defined IPv4 options have issues, as indicated in [BCP186]. This serves as an argument to refuse new option definitions for IPv4, even if the proposed IP options have no such issues, and have valid use cases on limited domains, or for limited end-host domains communicating over private networks or the public internet. This I-D defines a limited range of N IPv4 option numbers for variable assignment, by the user, to types of IP options to be used on limited domains and for limited end-host domains on the public internet. This will enable the use of IP options in two major use cases, without the need to fully standardize IP options, or register numbers for them in the IANA IP option numbers table.