SIP RFC protocol standards, but unfortunately are in English, can refer to

协议标准
........\RFC 2327(SDP).txt
........\RFC 2543(INVITE).txt
........\RFC 2806(TEL-URL).txt
........\RFC 2976(INFO).txt
........\RFC 3261(INVITE).txt
........\RFC 3262(PRACK) .txt
........\RFC 3265(SUBSCRIBE).txt
........\RFC 3311(UPDATE).txt
........\RFC 3326(Reason Header).txt
........\RFC 3428(MESSAGE).txt
........\RFC 3515(REFER).txt
........\RFC 3581(RPort).txt
........\RFC 3891(Replaces Header).txt
........\RFC 3892(Referred-By).txt
........\RFC 4028(Session Timers).txt
........\RFC 4475(Torture Test Messages).txt

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