This document specifies the general rules for an on-board data communication system between the different systems that may be used within public transport vehicles, based on the Internet Protocol (IPv4, [3] and IPv6, [4]). This includes operational support systems, passenger information systems, fare collection systems, etc.Cross References:RFC768RFC1035RFC2228RFC2616RFC4217RFC6763 RFC1123RFC3550RFC959RFC4291RFC3927RFC1305 ISO/IEC 20922RFC2460RFC7159RFC793RFC4330EN 61375-1RFC4862RFC2131RFC3177RFC5905RFC1918EN 13149 seriesRFC4253RFC2181RFC791RFC6762