| 2119 | Key words for use in RFCs to Indicate Requirement LevelsS. Bradner | Best Current Practice | March 1997 |
| 2234 | Augmented BNF for Syntax Specifications: ABNFD. Crocker, Ed., P. Overell · obsoleted by RFC 4234 | Proposed Standard | November 1997 |
| 2543 | SIP: Session Initiation ProtocolM. Handley, H. Schulzrinne, E. Schooler, J. Rosenberg · obsoleted by RFC 3261, RFC 3262, RFC 3263, RFC 3264, RFC 3265 | Proposed Standard | March 1999 |
| 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 |
| 2804 | IETF Policy on WiretappingIAB, IESG | Informational | May 2000 |
| 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 |
| 3428 | Session Initiation Protocol (SIP) Extension for Instant MessagingB. Campbell, Ed., J. Rosenberg, H. Schulzrinne, C. Huitema, D. Gurle | Proposed Standard | December 2002 |
| 3515 | The Session Initiation Protocol (SIP) Refer MethodR. Sparks | Proposed Standard | April 2003 |
| 3725 | Best Current Practices for Third Party Call Control (3pcc) in the Session Initiation Protocol (SIP)J. Rosenberg, J. Peterson, H. Schulzrinne, G. Camarillo | Best Current Practice | April 2004 |
| 3840 | Indicating User Agent Capabilities in the Session Initiation Protocol (SIP)J. Rosenberg, H. Schulzrinne, P. Kyzivat | Proposed Standard | August 2004 |
| 3851 | Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message SpecificationB. Ramsdell, Ed. · obsoleted by RFC 5751 | Proposed Standard | July 2004 |
| 3891 | The Session Initiation Protocol (SIP) "Replaces" HeaderR. Mahy, B. Biggs, R. Dean | Proposed Standard | September 2004 |
| 3892 | The Session Initiation Protocol (SIP) Referred-By MechanismR. Sparks | Proposed Standard | September 2004 |
| 3893 | Session Initiation Protocol (SIP) Authenticated Identity Body (AIB) FormatJ. Peterson | Proposed Standard | September 2004 |