| 2119 | Key words for use in RFCs to Indicate Requirement LevelsS. Bradner | Best Current Practice | March 1997 |
| 2434 | Guidelines for Writing an IANA Considerations Section in RFCsT. Narten, H. Alvestrand · obsoleted by RFC 5226 | Best Current Practice | October 1998 |
| 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 |
| 2976 | The SIP INFO MethodS. Donovan · obsoleted by RFC 6086 | Proposed Standard | October 2000 |
| 3261 | SIP: Session Initiation ProtocolJ. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, E. Schooler | Proposed Standard | July 2002 |
| 3262 | Reliability of Provisional Responses in Session Initiation Protocol (SIP)J. Rosenberg, H. Schulzrinne | Proposed Standard | July 2002 |
| 3265 | Session Initiation Protocol (SIP)-Specific Event NotificationA. B. Roach · obsoleted by RFC 6665 | Proposed Standard | July 2002 |
| 3311 | The Session Initiation Protocol (SIP) UPDATE MethodJ. Rosenberg | Proposed Standard | October 2002 |
| 3323 | A Privacy Mechanism for the Session Initiation Protocol (SIP)J. Peterson | Proposed Standard | December 2002 |
| 3325 | Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted NetworksC. Jennings, J. Peterson, M. Watson | Informational | December 2002 |
| 3420 | Internet Media Type message/sipfragR. Sparks | Proposed Standard | November 2002 |
| 3427 | Change Process for the Session Initiation Protocol (SIP)A. Mankin, S. Bradner, R. Mahy, D. Willis, J. Ott, B. Rosen · obsoleted by RFC 5727 | Best Current Practice | December 2002 |
| 3428 | Session Initiation Protocol (SIP) Extension for Instant MessagingB. Campbell, Ed., J. Rosenberg, H. Schulzrinne, C. Huitema, D. Gurle | Proposed Standard | December 2002 |
| 3487 | Requirements for Resource Priority Mechanisms for the Session Initiation Protocol (SIP)H. Schulzrinne | Informational | March 2003 |
| 3515 | The Session Initiation Protocol (SIP) Refer MethodR. Sparks | Proposed Standard | April 2003 |
| 3546 | Transport Layer Security (TLS) ExtensionsS. Blake-Wilson, M. Nystrom, D. Hopwood, J. Mikkelsen, T. Wright · obsoleted by RFC 4366 | Proposed Standard | June 2003 |
| 3550 | RTP: A Transport Protocol for Real-Time ApplicationsH. Schulzrinne, S. Casner, R. Frederick, V. Jacobson | Internet Standard | July 2003 |
| 3665 | Session Initiation Protocol (SIP) Basic Call Flow ExamplesA. Johnston, S. Donovan, R. Sparks, C. Cunningham, K. Summers | Best Current Practice | January 2004 |
| 3851 | Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message SpecificationB. Ramsdell, Ed. · obsoleted by RFC 5751 | Proposed Standard | July 2004 |
| 3893 | Session Initiation Protocol (SIP) Authenticated Identity Body (AIB) FormatJ. Peterson | Proposed Standard | September 2004 |
| 3903 | Session Initiation Protocol (SIP) Extension for Event State PublicationA. Niemi, Ed. | Proposed Standard | November 2004 |
| 4411 | Extending the Session Initiation Protocol (SIP) Reason Header for Preemption EventsJ. Polk | Proposed Standard | February 2006 |