| 2119 | Key words for use in RFCs to Indicate Requirement LevelsS. Bradner | Best Current Practice | March 1997 |
| 2782 | A DNS RR for specifying the location of services (DNS SRV)A. Gulbrandsen, P. Vixie, L. Esibov | Proposed Standard | February 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 |
| 3263 | Session Initiation Protocol (SIP): Locating SIP ServersJ. Rosenberg, H. Schulzrinne | Proposed Standard | July 2002 |
| 3428 | Session Initiation Protocol (SIP) Extension for Instant MessagingB. Campbell, Ed., J. Rosenberg, H. Schulzrinne, C. Huitema, D. Gurle | Proposed Standard | December 2002 |
| 3454 | Preparation of Internationalized Strings ("stringprep")P. Hoffman, M. Blanchet · obsoleted by RFC 7564 | Proposed Standard | January 2003 |
| 3856 | A Presence Event Package for the Session Initiation Protocol (SIP)J. Rosenberg | Proposed Standard | August 2004 |
| 3859 | Common Profile for Presence (CPP)J. Peterson | Proposed Standard | August 2004 |
| 3860 | Common Profile for Instant Messaging (CPIM)J. Peterson | Proposed Standard | August 2004 |
| 3966 | The tel URI for Telephone NumbersH. Schulzrinne | Proposed Standard | December 2004 |
| 3986 | Uniform Resource Identifier (URI): Generic SyntaxT. Berners-Lee, R. Fielding, L. Masinter | Internet Standard | January 2005 |
| 3987 | Internationalized Resource Identifiers (IRIs)M. Duerst, M. Suignard | Proposed Standard | January 2005 |
| 5122 | Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) for the Extensible Messaging and Presence Protocol (XMPP)P. Saint-Andre | Proposed Standard | February 2008 |
| 5234 | Augmented BNF for Syntax Specifications: ABNFD. Crocker, Ed., P. Overell | Internet Standard | January 2008 |
| 5246 | The Transport Layer Security (TLS) Protocol Version 1.2T. Dierks, E. Rescorla · obsoleted by RFC 8446, RFC 9846 | Proposed Standard | August 2008 |
| 5322 | Internet Message FormatP. Resnick, Ed. | Draft Standard | October 2008 |
| 5393 | Addressing an Amplification Vulnerability in Session Initiation Protocol (SIP) Forking ProxiesR. Sparks, Ed., S. Lawrence, A. Hawrylyshen, B. Campen | Proposed Standard | December 2008 |
| 5626 | Managing Client-Initiated Connections in the Session Initiation Protocol (SIP)C. Jennings, Ed., R. Mahy, Ed., F. Audet, Ed. | Proposed Standard | October 2009 |
| 5627 | Obtaining and Using Globally Routable User Agent URIs (GRUUs) in the Session Initiation Protocol (SIP)J. Rosenberg | Proposed Standard | October 2009 |
| 5630 | The Use of the SIPS URI Scheme in the Session Initiation Protocol (SIP)F. Audet | Proposed Standard | October 2009 |
| 5741 | RFC Streams, Headers, and BoilerplatesL. Daigle, Ed., O. Kolkman, Ed., IAB · obsoleted by RFC 7841 | Informational | December 2009 |
| 6120 | Extensible Messaging and Presence Protocol (XMPP): CoreP. Saint-Andre | Proposed Standard | March 2011 |
| 6121 | Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and PresenceP. Saint-Andre | Proposed Standard | March 2011 |
| 6122 | Extensible Messaging and Presence Protocol (XMPP): Address FormatP. Saint-Andre · obsoleted by RFC 7622 | Proposed Standard | March 2011 |
| 6347 | Datagram Transport Layer Security Version 1.2E. Rescorla, N. Modadugu · obsoleted by RFC 9147 | Proposed Standard | January 2012 |
| 6665 | SIP-Specific Event NotificationA.B. Roach | Proposed Standard | July 2012 |