IANA registers headers and their abbreviations.
| Abbreviation | Header | defined by | origin (mnemonic) |
|---|---|---|---|
| a | Accept-Contact | draft-ietf-sip-callerprefs | -- |
| b | Referred-By | -refer- | "by" |
| c | Content-Type | RFC 3261 | |
| e | Content-Encoding | RFC 3261 | |
| f | From | RFC 3261 | |
| i | Call-ID | RFC 3261 | |
| k | Supported | RFC 3261 | "know" |
| l | Content-Length | RFC 3261 | |
| m | Contact | RFC 3261 | "moved" |
| o | Event | -event- | "occurance" |
| r | Refer-To | -refer- | |
| s | Subject | RFC 3261 | |
| t | To | RFC 3261 | |
| u | Allow-Events | -events- | "understand" |
| v | Via | RFC 3261 |
Last updated by Henning Schulzrinne