1. Extending the SIP Reason Header with Warning Codes draft-hautakorpi-reason-header-for-warnings-00.txt

2. The Main Idea New protocol value for SIP Reason header field:
Warning codes from RFC3261.
Motivation: Ability to convey richer information about why a SIP request was generated.
Example:
Reason: SIP-Warning; cause=304;
text="Media type not available"

3. Example Scenario A Controller B INVITE 200 OK ACK INVITE
480 Temp. Unavailable
Warning: 399 pc2.example.org “Low battery”
ACK
BYE
Reason: SIP; cause=480; text="Request Terminated"
Reason: SIP-Warning; cause=399; text="Low battery"
200 OK

4. Way Forward One big open issue: Comments?
RFC3261 only allows Warning codes that are related to the SDP. Should this be the case also in the future?
Comments?