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ABNF for SIP Messages

see  ABNF in RFC 3261

SIP-message =
Request /  Response
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Request =
Request-Line  *( message-header )  CRLF  [ message-body ]
; see an example  Here
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Response =
Status-Line  *(  message-header )  CRLF  [ message-body ]
; see an example  Here
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Request-Line =
Method  SP  Request-URI  SP  SIP-Version  CRLF
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Status-Line =
SIP-Version  SP  Status-Code  SP  Reason-Phrase  CRLF
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Method =
INVITEm /  ACKm /  OPTIONSm /  BYEm /  CANCELm /  REGISTERm /  INFOm /  PRACKm /  SUBSCRIBEm /  NOTIFYm /  UPDATEm /  MESSAGEm /  REFERm /  PUBLISHm /  extension-method
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Request-URI =
SIP‑URI /  SIPS‑URI /  absoluteURI
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SIP-Version =
"SIP"   "/"   1*DIGIT  "."   1*DIGIT
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Reason-Phrase =
*( reserved /  unreserved /  escaped /  UTF8‑NONASCII /  UTF8‑CONT /  SP /  HTAB )
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message-header =
( < see   Headers  and   P‑Headers >   /
extension‑header )  CRLF
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message-body =
*OCTET
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extension-header =
header‑name   HCOLON   header‑value
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header-name =
token
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header-value =
*( TEXT‑UTF8char /  UTF8‑CONT /  LWS )
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extension-method =
token
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INVITEm =
%x49.4E.56.49.54.45
; INVITE in caps
;  RFC 3261 – Section 27.4
;  RFC 6026 – Section 9
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ACKm =
%x41.43.4B
; ACK in caps
;  RFC 3261 – Section 27.4
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OPTIONSm =
%x4F.50.54.49.4F.4E.53
; OPTIONS in caps
;  RFC 3261 – Section 27.4
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BYEm =
%x42.59.45
; BYE in caps
;  RFC 3261 – Section 27.4
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CANCELm =
%x43.41.4E.43.45.4C
; CANCEL in caps
;  RFC 3261 – Section 27.4
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REGISTERm =
%x52.45.47.49.53.54.45.52
; REGISTER in caps
;  RFC 3261 – Section 27.4
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INFOm =
%x49.4E.46.4F
; INFO in caps
;  RFC 6086 – Section 11.1
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PRACKm =
%x50.52.41.43.4B
; PRACK in caps
;  RFC 3262 – Section 6
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SUBSCRIBEm =
%x53.55.42.53.43.52.49.42.45
; SUBSCRIBE in caps
;  RFC 6665 – Section 8.1.1
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NOTIFYm =
%x4E.4F.54.49.46.59
; NOTIFY in caps
;  RFC 6665 – Section 8.1.2
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UPDATEm =
%x55.50.44.41.54.45
; UPDATE in caps
;  RFC 3311 – Section 10
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MESSAGEm =
%x4D.45.53.53.41.47.45
; MESSAGE in caps
;  RFC 3428 – Section 12
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REFERm =
%x52.45.46.45.52
; REFER in caps
;  RFC 3515 – Section 7
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PUBLISHm =
%x50.55.42.4C.49.53.48
; PUBLISH in caps
;  RFC 3903 – Section 13.1
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SIP Request example

INVITE sip:bob@biloxi.example.com SIP/2.0
Via: SIP/2.0/TCP client.atlanta.example.com:5060
;branch=z9hG4bK74bf9
Max-Forwards: 70
From: Alice <sip:alice@atlanta.example.com>
;tag=9fxced76sl
To: Bob <sip:bob@biloxi.example.com>
Call-ID: 3848276298220188511@atlanta.example.com
CSeq: 1 INVITE
Contact: <sip:alice@client.atlanta.example.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 151

v=0
o=alice  2890844526  2890844526  IN IP4 client.atlanta.example.com
s=-
c=IN  IP4  192.0.2.101
t=0 0
m=audio  49172  RTP/AVP 0
a=rtpmap:0  PCMU/8000

 

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SIP Response example

SIP/2.0 180 Ringing
Via: SIP/2.0/TCP  client.atlanta.example.com:5060
;branch=z9hG4bK74bf9
;received=192.0.2.101
From: Alice  <sip:alice@atlanta.example.com>
;tag=9fxced76sl
To: Bob  <sip:bob@biloxi.example.com>
;tag=8321234356
Call-ID: 3848276298220188511@atlanta.example.com
CSeq: 1 INVITE
Contact: <sip:bob@client.biloxi.example.com;transport=tcp>
Content-Length: 0

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