| 1319 | The MD2 Message-Digest AlgorithmB. Kaliski · obsoleted by RFC 6149 | Historic | April 1992 |
| 1321 | The MD5 Message-Digest AlgorithmR. Rivest | Informational | April 1992 |
| 2119 | Key words for use in RFCs to Indicate Requirement LevelsS. Bradner | Best Current Practice | March 1997 |
| 2617 | HTTP Authentication: Basic and Digest Access AuthenticationJ. Franks, P. Hallam-Baker, J. Hostetler, S. Lawrence, P. Leach, A. Luotonen, L. Stewart · obsoleted by RFC 7235, RFC 7615, RFC 7616, RFC 7617 | Draft Standard | June 1999 |
| 2818 | HTTP Over TLSE. Rescorla · obsoleted by RFC 9110 | Informational | May 2000 |
| 2974 | Session Announcement ProtocolM. Handley, C. Perkins, E. Whelan | Experimental | October 2000 |
| 3174 | US Secure Hash Algorithm 1 (SHA1)D. Eastlake 3rd, P. Jones | Informational | September 2001 |
| 3261 | SIP: Session Initiation ProtocolJ. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, E. Schooler | Proposed Standard | July 2002 |
| 3264 | An Offer/Answer Model with Session Description Protocol (SDP)J. Rosenberg, H. Schulzrinne | Proposed Standard | July 2002 |
| 3279 | Algorithms and Identifiers for the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) ProfileL. Bassham, W. Polk, R. Housley | Proposed Standard | May 2002 |
| 3280 | Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) ProfileR. Housley, W. Polk, W. Ford, D. Solo · obsoleted by RFC 5280 | Proposed Standard | May 2002 |
| 3525 | Gateway Control Protocol Version 1C. Groves, Ed., M. Pantaleo, Ed., T. Anderson, Ed., T. Taylor, Ed. · obsoleted by RFC 5125 | Historic | June 2003 |
| 3711 | The Secure Real-time Transport Protocol (SRTP)M. Baugher, D. McGrew, M. Naslund, E. Carrara, K. Norrman | Proposed Standard | March 2004 |
| 3851 | Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message SpecificationB. Ramsdell, Ed. · obsoleted by RFC 5751 | Proposed Standard | July 2004 |
| 4055 | Additional Algorithms and Identifiers for RSA Cryptography for use in the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) ProfileJ. Schaad, B. Kaliski, R. Housley | Proposed Standard | June 2005 |
| 4145 | TCP-Based Media Transport in the Session Description Protocol (SDP)D. Yon, G. Camarillo | Proposed Standard | September 2005 |
| 4234 | Augmented BNF for Syntax Specifications: ABNFD. Crocker, Ed., P. Overell · obsoleted by RFC 5234 | Draft Standard | October 2005 |
| 4251 | The Secure Shell (SSH) Protocol ArchitectureT. Ylonen, C. Lonvick, Ed. | Proposed Standard | January 2006 |
| 4288 | Media Type Specifications and Registration ProceduresN. Freed, J. Klensin · obsoleted by RFC 6838 | Best Current Practice | December 2005 |
| 4346 | The Transport Layer Security (TLS) Protocol Version 1.1T. Dierks, E. Rescorla · obsoleted by RFC 5246 | Historic | April 2006 |
| 4566 | SDP: Session Description ProtocolM. Handley, V. Jacobson, C. Perkins · obsoleted by RFC 8866 | Proposed Standard | July 2006 |
| 4571 | Framing Real-time Transport Protocol (RTP) and RTP Control Protocol (RTCP) Packets over Connection-Oriented TransportJ. Lazzaro | Proposed Standard | July 2006 |