图4-10是软交换之间的呼叫流程。

下面是软交换之间SIP消息的格式：

♦ INVITE

消息如下：

INVITE sip:66500002@191.169.1.116:5060;User=phone

SIP/2.0

Allow:INVITE,ACK,BYE,CANCEL,PRACK...；允许

From:<sip:7670000@191J694J12:5061;UseP=phone>;tag=446B5358336B534H)00()9820；发端

To:<sip:66500002@191.169.1.116:5060;User=phone>；收端

Supported: lOOrel

Content-Type:multipart/mixed;boundary=unique-boundary-1；内容

Call-ID:01F01A709DA1400000000001@191.169.1.112；呼叫 ID

CSeq:l INVITE

Expires:180；过期时间

Via:SIP/2.0/UDP 191.169.1.112:5061; branch^

Record-Route: <sip: 191.169.1.112;lr>

Contact:<sip:7670000@191.169.1.112:5061>

Max-Forwards:70；最大转发次数

Content-Length:597 ；内容长度

-unique-boundary-1

Content-Type:application/SDP

v=0

o=SoftX 1073741827 1073741827 IN IP4 191.169.1.112 s=Sip Call

c=IN IP4 191.169.1.45；连接

t=0 0

m=audio 14380 RTP/AVP 804 18；媒体类型 a=rtpmap:8 PCMA/8000 a=rtpmap:0 PCMU/8000 a=rtpmap:4 G723/8000 a=rtpmap:18 G729/8000

—unique-boundary-1

Content-Type:application/ISUP; version=；itu-t92+;base= itu-t92+

Content-Disposition: signal; handling=optional

01 00 20 00 0A 03 02 09 07 83 90 66 05 00 20 OF 08 01 00 0A 06 81 13 67 07 00 00 00

-unique-boundary-1—

♦SIP/2.0 100 Trying

消息如下：

Call-ID:01F01A709DA1400000000001@191.169.1.112

CSeq:l INVITE

Fmm:<sip:7670000@191.169丄112:5061;Useuphoiie>;ta沪446B5358336B534F00009820；发端

To:<sip:66500002@191.169.1.116:5060;User=phone>；收端

Via:SIP/2.0/UDP 191.169.1.112:5061;branch=

Content-Length:0

♦SIP/2.0 180 Ringing

消息如下：

Allow:INVITE,ACK,BYE,CANCEL,PRACK

Require: lOOrel

Supported: lOOrel

Via:SIP/2.0/UDP 191.169.1.112:5061

Call-ID:01F01A709DA1400000000001@191.169.1.112

CSeq:l INVITE

Fiom:<sip:7670000@ 191.169 丄 112:5061;Useuphone>;tag=446B5358336B534F00009820「发端 To:<sip:66500002@191.169.1.116:5060;Usen=phone>;tag=5358336B534F7A5F0021649B；收端

RSeq:633013647

Contact:<sip:66500002@191.169.1.116:5061>

Content-Length:4:内容长度

Content-Type:application/ISUP

06 C2 00 00

180中任选包含SDP信息

.PRACK

消息如下：

PRACK sip:66500002@191.169.1.116:5060;User=phone SIP/2.0

Call-ID:01F01A709DA1400000000001@191.169.1.112

CSeq:2 PRACK

From:<sip:767(XW@191.169.1.112:5()61;Usen=phone>;tag=446B5358336B534HX)0()9820；发端

To:<sip:66500002@ 191.169.1.116:5060;Usen=phone>;tag=5358336B534F7A5H)021649B ；收端

RAck:633013647 1 INVITE

Vh：SIP/2.0/UDP

191.169.1.112:5061;branch=898E03EElDBA24C581E03DB69E23FF0L80000001

Max-Forwards:70；最大转发次数

Content-Length:0 ；长度

♦SIP/2.0 200 OK

消息如下：

Call-ID:01F01A709DA1400000000001@191.169.1.112

CSeq:2 PRACK

FK)m:<sip:7670000@191.169.1.112:5061;UseF=phoiie>;tag=446B5358336B534F00009820；发端 Tb:<sip:66500002@191.169.1.116:5060;Usen=phone>;tag=5358336B534F7A5F0021649B;收端 Via:SIP/2.0/UDP

191.169.1.112:5061;branch=898E03EElDBA24C581E03DB69E23FF01.80000001

Content-Length:0 ；内容长度

♦SIP/2.0 200 OK

消息如下：

Content-Type:multipart/inixed;boundary=unique-boundary-l

Via:SIP/2.0/UDP 191.169.1.112:5061

Call-ID:01F01A709DA1400000000001@191.169.1.112；呼叫 ID

CSeq:l INVITE

From:<sip:7670000@191.169丄 112:5061;Usen=phog>;tag=446B5358336B534F00009820；发端

Ib:<sip:66500002@191.169.1.116:5060;Us^phone>;tag=5358336B534F7A5F0021649B；收端

Contact:<sip:66500002@191.169.1.116:5061>

Content-Length:298 ；长度

-unique-boundary-1

Content-Type:application/SDP；内容类型

v=0

o=SS 1073741851 1073741851 INIP4 191.169.1.116

s=Sip Call

c=IN IP4 191.169.1.35；连接

t=0 0

m=audio 30000 RTP/AVP & 媒体类型

a=rtpmap:8 PCMA/8000

-unique-boundary-1

Content-Type:application/ISUP; version=itu-t92+;base= itu-t92+

Content-Disposition: signal; handling=optional

09 01 1103C6 00 00 00

-unique-boundary-1—

♦ACK sip:66500002@ 191.169.1.116:5061 SIP/2.0

消息如下：

Call-ID:01F01A709DA1400000000001@191.169.1.112；呼叫 ID

CSeq:l ACK

From:<sip:7670000@191.169.1.112:5061;User=Thone>;tag=446B5358336B534F00009820；发端

To:<sip:66500002@ 191.169.1.116:5060;UseF=phone>;tag=5358336B534F7A5F0021649B ；收端

Via:SIP/2,0/UDP 191.169.1.112:5061

Max-Forwards:70；最大转发次数

Content-Length:0 ；长度

♦BYE

消息如下：

BYE sip:7670000@191.169.1.112:5061 SIP/2.0 Call-ID:01F01A709DA1400000000001@191.169.1.112；呼叫 ID

CSeq:l BYE