As VMS systems are introduced, there will be increasing exchanges of data between operators, particularly in terms of position data. For security purposes, it is essential that data transmission services that provide positive identification of both sender and receiver are used. This is most easily accomplished by relying upon X.25 and X.400 services. In the future, even voice band data over standard or ISDN telephone lines will provide suitable security when the telephony service provider transmits the telephone number of the calling party.
Regarding formats, there is no reason to vary from those used for transmission from vessel to VMS operations. As long as VMS stations are programmed to receive all three formats, the data can be transmitted just as received. Because the system used for transmission includes its own protocol to identify the sending party, no modifications need be necessary. The only imperative is that each VMS incorporate a security module which makes impossible reception of data from an unidentifiable source.