UDP MUST pass any IP option that it receives from the IP layer transparently to the application layer.
An application MUST be able to specify IP options to be sent in its UDP datagrams, and UDP MUST pass these options to the IP layer. DISCUSSION: At present, the only options that need be passed through UDP are Source Route, Record Route, and Time Stamp. However, new options may be defined in the future, and UDP need not and should not make any assumptions about the format or content of options it passes to or from the application; an exception to this might be an IP-layer security option.
An application based on UDP will need to obtain a source route from a request datagram and supply a reversed route for sending the corresponding reply.