Accept Accept‑Contact Accept‑Encoding Accept‑Language Accept‑Resource‑Priority Alert‑Info Allow Allow‑Events Answer‑Mode Authentication‑Info Authorization Call‑ID Call‑Info Contact Content‑Disposition Content‑Encoding Content‑ID Content‑Language Content‑Length Content‑Type CSeq Date Error‑Info Event Expires Feature‑Caps Flow‑Timer From Geolocation Geolocation‑Error Geolocation‑Routing History‑Info Identity Identity‑Info Info‑Package In‑Reply‑To Join Max‑Breadth Max‑Forwards MIME‑Version Min‑Expires Min‑SE Organization Path Permission‑Missing Policy‑Contact Policy‑ID Priority Privacy Priv‑Answer‑Mode Proxy‑Authenticate Proxy‑Authorization Proxy‑Require RAck Reason Record‑Route Recv‑Info Refer‑Events‑At Refer‑Sub Refer‑To Referred‑By Reject‑Contact Replaces Reply‑To Request‑Disposition Require Resource‑Priority Retry‑After Route RSeq Security‑Client Security‑Server Security‑Verify Server Service‑Route Session‑Expires Session-ID SIP‑ETag SIP‑If‑Match Subject Subscription‑State Supported Suppress‑If‑Match Target‑Dialog Timestamp To Trigger‑Consent Unsupported User‑Agent UUI (User‑to‑User) Via Warning WWW‑Authenticate