| 595 | Second thoughts in defense of the Telnet Go-AheadW. Hathaway | Unknown | December 1973 |
| 596 | Second thoughts on Telnet Go-AheadE.A. Taft | Unknown | December 1973 |
| 597 | Host statusN. Neigus, E.J. Feinler | Unknown | December 1973 |
| 598 | RFC index - December 5, 1973Network Information Center. Stanford Research Institute | Unknown | December 1973 |
| 599 | Update on NETRJSR.T. Braden · obsoleted by RFC 740 | Unknown | December 1973 |
| 600 | Interfacing an Illinois plasma terminal to the ARPANETA. Berggreen | Unknown | November 1973 |
| 601 | Traffic statistics (November 1973)A.M. McKenzie | Unknown | December 1973 |
| 602 | "The stockings were hung by the chimney with care"R.M. Metcalfe | Unknown | December 1973 |
| 603 | Response to RFC 597: Host statusJ.D. Burchfiel | Unknown | December 1973 |
| 604 | Assigned link numbersJ. Postel · obsoleted by RFC 739 | Unknown | December 1973 |
| 606 | Host names on-lineL.P. Deutsch | Unknown | December 1973 |
| 607 | Comments on the File Transfer ProtocolM. Krilanovich, G. Gregg · obsoleted by RFC 624 | Unknown | January 1974 |
| 608 | Host names on-lineM.D. Kudlick · obsoleted by RFC 810 | Unknown | January 1974 |
| 609 | Statement of upcoming move of NIC/NLS serviceB. Ferguson | Unknown | January 1974 |
| 610 | Further datalanguage design conceptsR. Winter, J. Hill, W. Greiff | Unknown | December 1973 |
| 611 | Two changes to the IMP/Host Protocol to improve user/network communicationsD.C. Walden | Unknown | February 1974 |
| 612 | Traffic statistics (December 1973)A.M. McKenzie | Unknown | January 1974 |
| 613 | Network connectivity: A response to RFC 603A.M. McKenzie | Unknown | January 1974 |
| 614 | Response to RFC 607: "Comments on the File Transfer Protocol"K.T. Pogran, N. Neigus | Unknown | January 1974 |
| 615 | Proposed Network Standard Data Pathname syntaxD. Crocker · obsoleted by RFC 645 | Unknown | March 1974 |
| 616 | LATEST NETWORK MAPSD. Walden | Unknown | February 1973 |
| 617 | Note on socket number assignmentE.A. Taft | Unknown | February 1974 |
| 618 | Few observations on NCP statisticsE.A. Taft | Unknown | February 1974 |
| 619 | Mean round-trip times in the ARPANETW. Naylor, H. Opderbeck | Unknown | March 1974 |
| 620 | Request for monitor host table updatesB. Ferguson | Unknown | March 1974 |
| 621 | NIC user directories at SRI ARCM.D. Kudlick | Unknown | March 1974 |
| 622 | Scheduling IMP/TIP down timeA.M. McKenzie | Unknown | March 1974 |
| 623 | Comments on on-line host name serviceM. Krilanovich | Unknown | February 1974 |
| 624 | Comments on the File Transfer ProtocolM. Krilanovich, G. Gregg, W. Hathaway, J.E. White | Unknown | February 1974 |
| 625 | On-line hostnames serviceM.D. Kudlick, E.J. Feinler | Unknown | March 1974 |
| 626 | On a possible lockup condition in IMP subnet due to message sequencingL. Kleinrock, H. Opderbeck | Unknown | March 1974 |
| 627 | ASCII text file of hostnamesM.D. Kudlick, E.J. Feinler | Unknown | March 1974 |
| 628 | Status of RFC numbers and a note on pre-assigned journal numbersM.L. Keeney | Unknown | March 1974 |
| 629 | Scenario for using the Network JournalJ.B. North | Unknown | March 1974 |
| 630 | FTP error code usage for more reliable mail serviceJ. Sussman | Unknown | April 1974 |
| 631 | International meeting on minicomputers and data communication: Call for papersA. Danthine | Unknown | April 1974 |
| 632 | Throughput degradations for single packet messagesH. Opderbeck | Unknown | May 1974 |
| 633 | IMP/TIP preventive maintenance scheduleA.M. McKenzie · obsoleted by RFC 638 | Unknown | March 1974 |
| 634 | Change in network address for Haskins LabA.M. McKenzie | Unknown | April 1974 |
| 635 | Assessment of ARPANET protocolsV. Cerf | Unknown | April 1974 |
| 636 | TIP/Tenex reliability improvementsJ.D. Burchfiel, B. Cosell, R.S. Tomlinson, D.C. Walden | Unknown | June 1974 |
| 637 | Change of network address for SU-DSLA.M. McKenzie | Unknown | April 1974 |
| 638 | IMP/TIP preventive maintenance scheduleA.M. McKenzie | Unknown | April 1974 |
| 640 | Revised FTP reply codesJ. Postel | Unknown | June 1974 |
| 642 | Ready line philosophy and implementationJ.D. Burchfiel | Unknown | July 1974 |
| 643 | Network Debugging ProtocolE. Mader | Unknown | July 1974 |
| 644 | On the problem of signature authentication for network mailR. Thomas | Unknown | July 1974 |
| 645 | Network Standard Data Specification syntaxD. Crocker | Unknown | June 1974 |
| 647 | Proposed protocol for connecting host computers to ARPA-like networks via front end processorsM.A. Padlipsky | Unknown | November 1974 |
| 651 | Revised Telnet status optionD. Crocker · obsoleted by RFC 859 | Unknown | October 1974 |
| 652 | Telnet output carriage-return disposition optionD. Crocker | Historic | October 1974 |
| 653 | Telnet output horizontal tabstops optionD. Crocker | Historic | October 1974 |
| 654 | Telnet output horizontal tab disposition optionD. Crocker | Historic | October 1974 |
| 655 | Telnet output formfeed disposition optionD. Crocker | Historic | October 1974 |
| 656 | Telnet output vertical tabstops optionD. Crocker | Historic | October 1974 |
| 657 | Telnet output vertical tab disposition optionD. Crocker | Historic | October 1974 |
| 658 | Telnet output linefeed dispositionD. Crocker | Historic | October 1974 |
| 659 | Announcing additional Telnet optionsJ. Postel | Unknown | October 1974 |
| 660 | Some changes to the IMP and the IMP/Host interfaceD.C. Walden | Unknown | October 1974 |
| 661 | Protocol informationJ. Postel | Unknown | November 1974 |
| 662 | Performance improvement in ARPANET file transfers from MulticsR. Kanodia | Unknown | November 1974 |
| 663 | Lost message detection and recovery protocolR. Kanodia | Unknown | November 1974 |
| 666 | Specification of the Unified User-Level ProtocolM.A. Padlipsky | Unknown | November 1974 |
| 667 | Host PortsS.G. Chipman | Unknown | December 1974 |
| 669 | November, 1974, survey of New-Protocol Telnet serversD.W. Dodds | Unknown | December 1974 |
| 671 | Note on Reconnection ProtocolR. Schantz | Unknown | December 1974 |
| 672 | Multi-site data collection facilityR. Schantz | Unknown | December 1974 |
| 674 | Procedure call documents: Version 2J. Postel, J.E. White | Unknown | December 1974 |
| 675 | Specification of Internet Transmission Control ProgramV. Cerf, Y. Dalal, C. Sunshine · obsoleted by RFC 7805 | Historic | December 1974 |
| 677 | Maintenance of duplicate databasesP.R. Johnson, R. Thomas | Unknown | January 1975 |
| 678 | Standard file formatsJ. Postel | Unknown | December 1974 |
| 679 | February, 1975, survey of New-Protocol Telnet serversD.W. Dodds | Unknown | February 1975 |
| 680 | Message Transmission ProtocolT.H. Myer, D.A. Henderson | Unknown | April 1975 |
| 681 | Network UNIXS. Holmgren | Unknown | March 1975 |
| 683 | FTPSRV - Tenex extension for paged filesR. Clements | Unknown | April 1975 |
| 684 | Commentary on procedure calling as a network protocolR. Schantz | Unknown | April 1975 |
| 685 | Response time in cross network debuggingM. Beeler | Unknown | April 1975 |
| 686 | Leaving well enough aloneB. Harvey | Unknown | May 1975 |
| 687 | IMP/Host and Host/IMP Protocol changesD.C. Walden · obsoleted by RFC 704 | Unknown | June 1975 |
| 688 | Tentative schedule for the new Telnet implementation for the TIPD.C. Walden | Unknown | June 1975 |
| 689 | Tenex NCP finite state machine for connectionsR. Clements | Unknown | May 1975 |
| 690 | Comments on the proposed Host/IMP Protocol changesJ. Postel | Unknown | June 1975 |
| 691 | One more try on the FTPB. Harvey | Unknown | June 1975 |
| 692 | Comments on IMP/Host Protocol changes (RFCs 687 and 690)S.M. Wolfe | Unknown | June 1975 |