RFC 3261 – SIP: Session Initiation Protocol

Core specification of the current revision of SIP.

In Short


Status Codes
Header Fields

Cross Reference

RFC 3261 references

RFC 3261 is referenced by


The following sections of RFC 3261 have been updated:


See also the IETF tools' status page for draft-ietf-sip-rfc2543bis


Jonathan Rosenberg on [email protected], message <[email protected]>:

[H]ere are the changes:

1. single consolidated "changes from rfc2543" section, listing major stuff.

2. BNF converted to rfc2234, countless bugs fixed based on comments

3. new loose route text incorporated. Please read this. The text is different from what Robert had described on the list. Whilst incorporating that text, we ran into a case that didn't work. TUrns out the fix simplified the whole thing even further. Based on robert's note, a proxy that wanted to route to a strict router would need to dig up the first loose router in a route set, say A, and replace that route entry with A, target, A, where target is the current r-uri. That is not the case now; it simply appends the r-uri to the bottom-most route element. This improves the backwards compatibility story, improves proxy performance, and makes things much more self consistent. Proxy processing of route/record-route is now shrunk considerably from bis-05 and bis-06.

4. split references into normative and non-normative.

5. incorporated text on generalized offer/answer mappings to SIP requests and responses

6. Reduced usage of 70 as max-forwards value from MUST to SHOULD

7. Included fix for open issue #58. When UAS generates an offer in a 2xx to re-invite, it uses the broadest SDP possible that it belives will not be rejected by its peer.

8. Added some S/MIME error cases.

9. Fixed normative strengths of S/MIME support (MUST for signed-data and certs-only).

10. Strengthened TLS/IPSec wording (fixing nits).

11. S/MIME should now be able to reuse root CAs used to verify TLS/IPSec keys.

12. Added brief statement to start of threat model section describing threat environment.

13. Added eavesdropping to threats based on body modification.

14. clarified conditions under which multiple headers can be folded into one header with comma separated values. Also pointed out exception for the Auth headers.

15. Max-Forwards needs to be between 1 and 255.

16. Added anonymous username and password for digest.

17. Clarified usage of timestamp delay parameter.

RFC 3261

Excerpts from RFCs and Internet Drafts: Copyright © The Internet Society. All Rights Reserved.
All other material is copyrighted by the contributing authors and licensed to the public under the GNU Free Documentation License (GFDL).
For more information, please see the Copyright page.