5.4.10 409 Conflict 5.4.11 410 Gone 5.4.12 411 Length Required 5.4.13 413 Request Entity Too Large 5.4.14 414 Request-URI Too Long 5.4.15 415 Unsupported Media Type 5.4.16 416 Unsupported URI Scheme 5.4.17 420 Bad Extension 5.4.18 421 Extension Required 5.4.19 422 Session Timer Interval Too Small 5.4.20 423 Interval Too Brief 5.4.21 428 Use Authentication Token 5.4.22 429 Provide Referror Identity 5.4.23 480 Temporarily Unavailable 5.4.24 481 Dialog/Transaction Does Not Exist 5.4.25 482 Loop Detected 5.4.26 483 Too Many Hops 5.4.27 484 Address Incomplete 5.4.28 485 Ambiguous 5.4.29 486 Busy Here 5.4.30 487 Request Terminated 5.4.31 488 Not Acceptable Here Contents 5.4.32 489 Bad Event 5.4.33 491 Request Pending 5.4.34 493 Request Undecipherable Server Error 5.5.1 500 Server Internal Error 5.5.2 501 Not Implemented 5.5.3 502 Bad Gateway 5.5.4 503 Service Unavailable 5.5.5 504 Gateway Timeout 5.5.6 505 Version Not Supported 5.5.7 513 Message Too Large Global Error 5.6.1 600 Busy Everywhere 5.6.2 603 Decline 5.6.3 604 Does Not Exist Anywhere 5.6.4 606 Not Acceptable References SIP Header Fields Request and Response Header Fields 6.1.1 Alert-Info 6.1.2 Allow-Events 6.1.3 Call-ID 6.1.4 Contact 6.1.5 6.1.6 6.1.7 Encryption 6.1.8 6.1.9 Organization 6.1.10 Record-Route 6.1.11 Retry-After 6.1.12 Subject 6.1.13 Supported 6.1.14 Timestamp 6.1.15 6.1.16 User-Agent SIP: Understanding the Session Initiation Protocol 6.1.17 Request Header Fields 6.2.1 Accept 6.2.2 Accept-Contact 6.2.3 Accept-Encoding 6.2.4 Accept-Language 6.2.5 Authorization 6.2.6 Call-Info 6.2.7 Event 6.2.8 6.2.9 In-Reply-To 6.2.10 6.2.11 Priority 6.2.12 Privacy 6.2.13 Proxy-Authorization 6.2.14 Proxy-Require 6.2.15 P-OSP-Auth-Token 6.2.16 P-Asserted-Identity 6.2.17 P-Preferred-Identity 6.2.18 Max-Forwards 6.2.19 Reason 6.2.20 Refer-To 6.2.21 Referred-By 6.2.22 Reply-To 6.2.23 Replaces 6.2.24 Reject-Contact 6.2.25 Request-Disposition 6.2.26 Require 6.2.27 Response-Key 6.2.28 Route 6.2.29 6.2.30 Session-Expires 6.2.31 Subscription-State Response Header Fields 6