Editing ARPANET (section)

=== 1822 protocol ===

The starting point for host-to-host communication on the ARPANET in 1969 was the [[1822 protocol]], which defined the transmission of messages to an IMP.<ref>{{cite tech report |url=http://www.bitsavers.org/pdf/bbn/imp/BBN1822_Jan1976.pdf |title=Interface Message Processor: Specifications for the Interconnection of a Host and an IMP |id=Report No. 1822 |publisher=Bolt Beranek and Newman, Inc. (BBN)}}</ref> The message format was designed to work unambiguously with a broad range of computer architectures. An 1822 message essentially consisted of a message type, a numeric host address, and a data field. To send a data message to another host, the transmitting host formatted a data message containing the destination host's address and the data message being sent, and then transmitted the message through the 1822 hardware interface. The IMP then delivered the message to its destination address, either by delivering it to a locally connected host, or by delivering it to another IMP. When the message was ultimately delivered to the destination host, the receiving IMP would transmit a ''Ready for Next Message'' (RFNM) acknowledgment to the sending, host IMP.{{citation needed|date=October 2022}}