SIP基本呼叫

我们首先来看下主要的呼叫流程。

INVITEsip:[email protected];user=phone SIP/2.0

From:"+861069690069"<sip:[email protected];user=phone>;tag=8741b8-ac1014d2-13c4-1c6-10e9bfd8-1c6

To:<sip:[email protected];user=phone>

Call-ID: [email protected]

CSeq: 1 INVITE

Via: SIP/2.0/UDP172.16.20.210:5060;branch=z9hG4bK-1c6-6f0cc-66d0e581

Allow: INVITE,ACK,CANCEL,BYE,REGISTER,REFER,NOTIFY,PRACK,CANCEL,SUBSCRIBE,OPTIONS,INFO,UPDATE,MESSAGE

Max-Forwards: 70

Supported: 100rel,replaces,timer

P-Preferred-Identity:"+861069690069"<sip:[email protected];user=phone>

Contact: <sip:[email protected]:5060>

Content-Type: application/SDP

Content-Length: 236

 

v=0

o=+861069690069 454 454 IN IP4172.16.20.210

s=-

c=IN IP4 172.16.20.210

t=0 0

m=audio 10008 RTP/AVP 8 0 18 4

a=rtpmap:8 PCMA/8000

a=rtpmap:0 PCMU/8000

a=rtpmap:18 G729/8000

a=rtpmap:4 G723/8000

a=ptime:20

a=ecan:fb on -

 

用户摘机发起一路呼叫，终端+861069690069向代理server发送INVITE请求

 

SIP/2.0 100 Trying

Via: SIP/2.0/UDP172.16.20.210:5060;branch=z9hG4bK-1c6-6f0cc-66d0e581;received=192.168.100.41

Call-ID: [email protected]

From: "+861069690069"<sip:[email protected];user=phone>;tag=8741b8-ac1014d2-13c4-1c6-10e9bfd8-1c6

To:<sip:[email protected];user=phone>

CSeq: 1 INVITE

Content-Length: 0

 

代理server收到终端发送的INVITE请求，向终端+861069690069发送100 trying说明该请求已经收到，让终端停止INVITE重发定时器。

 

INVITEsip:[email protected]:5060 SIP/2.0

Via: SIP/2.0/UDP192.168.246.210:5060;branch=z9hG4bKw0hwph6xp20yo0gg2zhmwwpvmT25426

Call-ID: [email protected]

From:<sip:[email protected]>;tag=sbc05100m0qlxw6

To:<sip:[email protected];user=phone>

CSeq: 1 INVITE

Allow:INVITE,CANCEL,ACK,BYE,OPTIONS,INFO,UPDATE,PRACK,REFER,NOTIFY,REGISTER,MESSAGE,SUBSCRIBE

Contact:<sip:192.168.246.210:5060>

Max-Forwards: 69

Supported: 100rel,replaces,timer

P-Asserted-Identity:<tel:+861069690069>

Privacy: none

P-Called-Party-ID:<sip:[email protected]>

Content-Length: 235

Content-Type: application/sdp

 

v=0

o=- 454 454 IN IP4 192.168.246.218

s=SBC call

c=IN IP4 192.168.246.218

t=0 0

m=audio 12962 RTP/AVP 8 0 18 4

a=rtpmap:8 PCMA/8000

a=rtpmap:0 PCMU/8000

a=rtpmap:18 G729/8000

a=rtpmap:4 G723/8000

a=ptime:20

a=ecan:fb on –

 

代理server通过对INVITE请求的验证通过后，检查via头域中是否包括自己的地址。若已包括自己的地址，说明已经发生回路，向终端+861069690069发送错误的应答；假设没有问题，代理server在请求消息的via头域插入自己的地址，并向INVITE消息的to头域所指的被叫终端转发INVITE请求。

 

SIP/2.0  100 Trying

From:<sip:[email protected]>;tag=sbc05100m0qlxw6

To:<sip:[email protected];user=phone>

Call-ID: [email protected]

CSeq: 1 INVITE

Via: SIP/2.0/UDP192.168.246.210:5060;branch=z9hG4bKw0hwph6xp20yo0gg2zhmwwpvmT25426

Supported: 100rel,replaces,timer

P-Preferred-Identity:"+861069690067"<sip:[email protected];user=phone>

Contact:<sip:[email protected]:5060>

Content-Length: 0

 

终端+861069690067收到代理server发送的INVITE请求，并向代理server发送100 trying说明该请求已经收到，让终端停止INVITE重发定时器。

SIP/2.0 180 Ringing

From:<sip:[email protected]>;tag=sbc05100m0qlxw6

To:<sip:[email protected];user=phone>;tag=874368-ac1014d2-13c4-1c7-26f60a2f-1c7

Call-ID: [email protected]

CSeq: 1 INVITE

Via: SIP/2.0/UDP192.168.246.210:5060;branch=z9hG4bKw0hwph6xp20yo0gg2zhmwwpvmT25426

Supported: 100rel,replaces,timer

P-Preferred-Identity: "+861069690067"<sip:[email protected];user=phone>

Contact:<sip:[email protected]:5060>

Content-Length: 0

 

被叫终端对INVITE消息的合法性检查通过，指示代理server振铃，向代理server发送180 ring消息

 

SIP/2.0 180 Ringing

Via: SIP/2.0/UDP172.16.20.210:5060;branch=z9hG4bK-1c6-6f0cc-66d0e581;received=192.168.100.41

Call-ID:[email protected]

From:"+861069690069"<sip:[email protected];user=phone>;tag=8741b8-ac1014d2-13c4-1c6-10e9bfd8-1c6

To:<sip:[email protected];user=phone>;tag=sbc0509wwxwpz1q

CSeq: 1 INVITE

Allow:INVITE,CANCEL,ACK,BYE,OPTIONS,INFO,UPDATE,PRACK,REFER,NOTIFY,REGISTER,MESSAGE,SUBSCRIBE

Contact:<sip:192.168.246.210:5060>

P-Asserted-Identity:<sip:[email protected]>,<tel:+861069690067>

Content-Length: 0

 

代理server收到180 ring消息，指示主叫方听回铃音

 

SIP/2.0 200 OK

From:<sip:[email protected]>;tag=sbc05100m0qlxw6

To:<sip:[email protected];user=phone>;tag=874368-ac1014d2-13c4-1c7-26f60a2f-1c7

Call-ID:[email protected]

CSeq: 1 INVITE

Allow: INVITE,ACK,CANCEL,BYE,REGISTER,REFER,NOTIFY,PRACK,CANCEL,SUBSCRIBE,OPTIONS,INFO,UPDATE,MESSAGE

Via: SIP/2.0/UDP192.168.246.210:5060;branch=z9hG4bKw0hwph6xp20yo0gg2zhmwwpvmT25426

Supported: 100rel,replaces,timer

P-Preferred-Identity:"+861069690067"<sip:[email protected];user=phone>

Contact:<sip:[email protected]:5060>

Content-Type: application/SDP

Content-Length: 248

 

v=0

o=+861069690067 456 456 IN IP4172.16.20.210

s=-

c=IN IP4 172.16.20.210

t=0 0

m=audio 10012 RTP/AVP 8 0 18 4

a=rtpmap:8 PCMA/8000

a=rtpmap:0 PCMU/8000

a=rtpmap:18 G729/8000

a=rtpmap:4 G723/8000

a=ptime:20

a=ecan:fb on -

a=sendrecv

 

被叫方摘机，向代理server发送200OK消息，表示已经摘机能够開始通话了

 

SIP/2.0 200 OK

Via: SIP/2.0/UDP172.16.20.210:5060;branch=z9hG4bK-1c6-6f0cc-66d0e581;received=192.168.100.41

Call-ID: [email protected]

From:"+861069690069"<sip:[email protected];user=phone>;tag=8741b8-ac1014d2-13c4-1c6-10e9bfd8-1c6

To:<sip:[email protected];user=phone>;tag=sbc0509wwxwpz1q

CSeq: 1 INVITE

Allow:INVITE,CANCEL,ACK,BYE,OPTIONS,INFO,UPDATE,PRACK,REFER,NOTIFY,REGISTER,MESSAGE,SUBSCRIBE

Contact:<sip:192.168.246.210:5060>

Supported: 100rel,replaces,timer

P-Asserted-Identity:<sip:[email protected]>,<tel:+861069690067>

Content-Length: 247

Content-Type: application/sdp

 

v=0

o=- 456 456 IN IP4 192.168.246.218

s=SBC call

c=IN IP4 192.168.246.218

t=0 0

m=audio 12964 RTP/AVP 8 0 18 4

a=rtpmap:8 PCMA/8000

a=rtpmap:0 PCMU/8000

a=rtpmap:18 G729/8000

a=rtpmap:4 G723/8000

a=ptime:20

a=ecan:fb on -

a=sendrecv

 

代理server收到200 OK消息后改动状态机，而且发送200OK消息到主叫，告诉主叫，被叫已经接通

 

ACK sip:192.168.246.210:5060SIP/2.0

From:"+861069690069"<sip:[email protected];user=phone>;tag=8741b8-ac1014d2-13c4-1c6-10e9bfd8-1c6

To:<sip:[email protected];user=phone>;tag=sbc0509wwxwpz1q

Call-ID:[email protected]

CSeq: 1 ACK

Via: SIP/2.0/UDP172.16.20.210:5060;branch=z9hG4bK-1c8-6f6ac-7e19e755

Max-Forwards: 70

P-Preferred-Identity:"+861069690069"<sip:[email protected];user=phone>

Contact:<sip:[email protected]:5060>

Content-Length: 0

 

代理server收到ACK后，向被叫方发送200 OK相应的ACK消息，表示200 OK消息已经收到，而且主叫和被叫能够进行通话

 

ACKsip:[email protected]:5060 SIP/2.0

Via: SIP/2.0/UDP192.168.246.210:5060;branch=z9hG4bKw0wp6h1p6ovh1lzr1lgr1rpzmT25427

Call-ID:[email protected]

From:<sip:[email protected]>;tag=sbc05100m0qlxw6

To:<sip:[email protected];user=phone>;tag=874368-ac1014d2-13c4-1c7-26f60a2f-1c7

CSeq: 1 ACK

Max-Forwards: 69

Content-Length: 0

 

被叫发送收到ACK消息后，通话建立成功

 

语音通讯建立成功，開始进行正常的语音通话……

 

BYE sip:192.168.246.210:5060SIP/2.0

From:<sip:[email protected];user=phone>;tag=874368-ac1014d2-13c4-1c7-26f60a2f-1c7

To:<sip:[email protected]>;tag=sbc05100m0qlxw6

Call-ID: [email protected]

CSeq: 1 BYE

Via: SIP/2.0/UDP172.16.20.210:5060;branch=z9hG4bK-1d1-719f3-76b3cbbd

Max-Forwards: 70

Supported: 100rel,replaces,timer

P-Preferred-Identity:"+861069690067"<sip:[email protected];user=phone>

Content-Length: 0

 

主叫方挂机，向代理server发送BYE消息

 

SIP/2.0 200 OK

Via: SIP/2.0/UDP172.16.20.210:5060;branch=z9hG4bK-1d1-719f3-76b3cbbd;received=192.168.100.41

Call-ID:[email protected]

From: <sip:[email protected];user=phone>;tag=874368-ac1014d2-13c4-1c7-26f60a2f-1c7

To:<sip:[email protected]>;tag=sbc05100m0qlxw6

CSeq: 1 BYE

Content-Length: 0

 

代理server收到，BYE消息后，确认挂机后，向主叫方发送200OK，表示主叫方已经成功挂机，而且向被叫方发送BYE消息，通知其挂机

 

BYEsip:[email protected]:5060 SIP/2.0

Via: SIP/2.0/UDP 192.168.246.210:5060;branch=z9hG4bKlvog2lhovvv0w6pmllymrhl16T15221

Call-ID: [email protected]

From:<sip:[email protected];user=phone>;tag=sbc0509wwxwpz1q

To:"+861069690069"<sip:[email protected];user=phone>;tag=8741b8-ac1014d2-13c4-1c6-10e9bfd8-1c6

CSeq: 1 BYE

Max-Forwards: 69

Reason: Q.850;cause=16

Content-Length: 0

 

代理server向被叫发送关机消息BYE，告诉被叫主叫已经挂机

 

SIP/2.0 200 OK

From:<sip:[email protected];user=phone>;tag=sbc0509wwxwpz1q

To: "+861069690069"<sip:[email protected];user=phone>;tag=8741b8-ac1014d2-13c4-1c6-10e9bfd8-1c6

Call-ID: [email protected]

CSeq: 1 BYE

Via: SIP/2.0/UDP192.168.246.210:5060;branch=z9hG4bKlvog2lhovvv0w6pmllymrhl16T15221

Supported: 100rel,replaces,timer

P-Preferred-Identity:"+861069690069"<sip:[email protected];user=phone>

Content-Length: 0

 

被叫方收到BYE消息后，确认挂机，而且回复200OK，表示挂机操作已经成功完毕

呼叫消息的流程图

 

依据上述的呼叫信息，对其进行具体的解说。

1）  主叫方“+861069690069”发起语音呼叫，主叫方地址：172.16.20.210，向代理server（192.168.246.210:）发送INVITE请求，须要和被叫方“69690067”建立呼叫。

2）  代理server收到主叫方，发送的INVITE请求后，回复100 Trying。100 Trying表示代理server已经收到了INVITE请求，不须要UAC，即主叫方启用INVITE重发定时间，再次发送INVITE消息。

3）  代理server对收到的INVITE消息进行合法性检查，检查通过后，在注冊server上查找被叫，是否存在这种注冊被叫号码，假设被叫不存在向主叫方发送404消息结束本次呼叫请求，否则，想被叫注冊的地址发送呼叫请求INVITE消息。

4）  被叫方收到INVITE请求消息后，回复100 Trying。并对INVITE消息的合法性检測。

5）  被叫方对INVITE消息的合法性检測通过后，開始振铃，而且向代理server发送180，表示被叫方開始振铃，主叫方听回铃音或彩铃。

6）  代理server收到180后，改动代理server的状态机状态，改动为振铃状态，而且发送振铃消息给主叫方，主叫方听回铃音。

7）  被叫方摘机，向代理server发送200OK消息，表示被叫方已经摘机。

8）  代理server收到200OK消息后改动状态机，而且发送200OK消息到主叫，告诉主叫，被叫已经接通。

9）  主叫收到200OK后，打开媒体通道，建立通话，而且向代理server发送ACK消息，表示已经收到200OK消息。

10）代理server收到ACK后，向被叫方发送200OK相应的ACK消息，表示200OK消息已经收到，而且主叫和被叫能够进行通话。

11） 被叫发送收到ACK消息后，通话建立成功。

12）通过以上11个步骤，通话最终建立成功。

13）主叫方挂机，向代理server发送BYE消息。

14）代理server收到，BYE消息后，确认挂机后，向主叫方发送200OK，表示主叫方已经成功挂机，而且向被叫方发送BYE消息，通知其挂机。

15） 被叫方收到BYE消息后，确认挂机，而且回复200OK，表示挂机操作已经成功完毕。

16） 经过以上步骤，通话到此结束。