SIP请求消息实例: Request-Line: INVITE sip:8882101@10.77.226.41 SIP/2.0(开始行:INVITE + URL+SIP的版本号) Message Header(消息头) From: sip:8882100@10.77.226.41;tag=1c13959(From:说明本次会话是由谁发起的) To: sip:8882101@10.77.226.41(To:说明本消息是送给谁的) Call-Id: call-973574765-4@10.77.226.121(CALL-ID:用来唯一标识一次SIP呼叫的编号) Cseq: 1 INVITE(Cseq:用来区分同一个呼叫不同INVITE消息的编号) Content-Type: application/sdp(Content-Type:用来说明消息体的类型) Content-Length: 199(Content-Length:用来说明消息体的长度) Accept-Language: en(Accept-Language:用来说明消息体语言类型) Contact: sip:8882100@10.77.226.121(Contact:用来告诉对方回信息给谁) User-Agent: Pingtel/1.0.0 (VxWorks)(User-Agent:指明UA的用户类型) Via: SIP/2.0/UDP 10.77.226.121(Via:记录消息的地址路径) Session Description Protocol(SDP) Session Description, version (v): 0(SDP版本号) Owner/Creator, Session Id (o): IN IP4 10.77.226.121(描述源端信息) Session Name (s): phone-call(SDP本次呼叫名字) Connection Information (c): IN IP4 10.77.226.121(本端IP信息) Time Description, active time (t): 0 0 Media Description, name and address (m): audio 8766 RTP/AVP 0 96 8(RTP媒体类型描述) Media Attribute (a): rtpmap:0 pcmu/8000/1(支持PCMU率压缩编码方式) Media Attribute (a): rtpmap:96 telephone-event/8000/1(支持telephone-event) Media Attribute (a): rtpmap:8 pcma/8000/1(支持PCMA率压缩编码方式) 该消息用来指明本次呼叫需要由谁和谁参与,采用那种媒体类型。
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