http://www.rfc-editor.org/rfc/rfc0674.txt
RFC 0674: Procedure call documents: Version 2, J. Postel, J.E. White1974-12-01T23:00:00-00:00Host level protocol used in the NSW--a slightly constrained version of ARPANET Host-to-Host protocol, affecting allocation, RFNM wait, and retransmission; see also RFC 684.