7.2. Basic Message Flow with Connected Identity (RFC 4916) (连接身份的基本消息流)
前一示例未展示将 RFC 4916 用于连接身份 (connected identity). 以下示例展示该用法:
Alice Proxies Bob |(1) INVITE | | |---------------->| | | |(2) INVITE | | |----------------->| | |(3) hello | |<-----------------------------------| |(4) hello | | |----------------------------------->| | |(5) finished | |<-----------------------------------| | |(6) media | |<-----------------------------------| |(7) finished | | |----------------------------------->| | |(8) 200 OK | |<-----------------------------------| |(9) ACK | | |----------------------------------->| | |(10) UPDATE | | |<-----------------| |(11) UPDATE | | |<----------------| | |(12) 200 OK | | |---------------->| | | |(13) 200 OK | | |----------------->| | |(14) media | |<---------------------------------->|
本例前 9 条消息与先前相同. 消息 (10)–(13) 为执行 RFC 4916 的 UPDATE, 属新增内容.
Message (10): UPDATE Bob -> Proxy
Bob 向 Alice 发送符合 RFC 4916 的 UPDATE, 其中包含其指纹. 该 UPDATE 的会话信息与他在 200 OK (消息 8) 中提供的一致. 原则上 UPDATE 也可用于修改会话参数, 但此处仅用于确认指纹.
UPDATE sip:[email protected] SIP/2.0
Via: SIP/2.0/TLS ua2.example.com;branch=z9hG4bK-0e53sadfkasldkfj
To: "Alice" <sip:[email protected]>;tag=843c7b0b
From <sip:[email protected]>;tag=6418913922105372816
Route: <sip:proxy.example.com;lr>
Call-ID: 6076913b1c39c212@REVMTEpG
CSeq: 2 UPDATE
Contact: <sip:ua2.example.com>
Content-Type: application/sdp
Content-Length: xxxx
Supported: from-change
Max-Forwards: 70
v=0
o=- 6418913922105372816 2105372818 IN IP4 ua2.example.com
s=example2
c=IN IP4 ua2.example.com
a=setup:active
a=fingerprint: SHA-1 \
FF:FF:FF:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB
t=0 0
m=audio 12000 UDP/TLS/RTP/SAVP 0
a=acfg:1 t=1
Message (11): UPDATE Proxy -> Alice
UPDATE 由 Bob (及 Alice 的代理) 转发至 Alice. Bob 的代理插入了 Identity 与 Identity-Info 头字段. 同上, 为简化将两侧代理画成单一元素. Alice 验证所提供的身份. (注意: 文中的身份签名仅为示例, 并非正确值.)
UPDATE sip:[email protected] SIP/2.0
Via: SIP/2.0/TLS proxy.example.com;branch=z9hG4bK-0e53sadfkasldkfj
Via: SIP/2.0/TLS ua2.example.com;branch=z9hG4bK-0e53sadfkasldkfj
To: "Alice" <sip:[email protected]>;tag=843c7b0b
From <sip:[email protected]>;tag=6418913922105372816
Call-ID: 6076913b1c39c212@REVMTEpG
CSeq: 2 UPDATE
Contact: <sip:[email protected]>
Content-Type: application/sdp
Content-Length: xxxx
Supported: from-change
Max-Forwards: 69
Identity: CyI4+nAkHrH3ntmaxgr01TMxTmtjP7MASwliNRdupRI1vpkXRvZXx1ja9k
3W+v1PDsy32MaqZi0M5WfEkXxbgTnPYW0jIoK8HMyY1VT7egt0kk4XrKFC
HYWGCl0nB2sNsM9CG4hq+YJZTMaSROoMUBhikVIjnQ8ykeD6UXNOyfI=
Identity-Info: https://example.com/cert
v=0
o=- 6418913922105372816 2105372818 IN IP4 ua2.example.com
s=example2
c=IN IP4 ua2.example.com
a=setup:active
a=fingerprint: SHA-1 \
FF:FF:FF:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB
t=0 0
m=audio 12000 UDP/TLS/RTP/SAVP 0
a=acfg:1 t=1
Message (12): 200 OK Alice -> Bob
Alice 对 Bob 的 UPDATE 返回 200 OK. 因 Bob 仅重发其在 200 OK 中的相同会话参数, Alice 亦可重放其对会话参数的视图.
SIP/2.0 200 OK
To: "Alice" <sip:[email protected]>;tag=843c7b0b
From <sip:[email protected]>;tag=6418913922105372816
Via: SIP/2.0/TLS proxy.example.com;branch=z9hG4bK-0e53sadfkasldkfj
Via: SIP/2.0/TLS ua2.example.com;branch=z9hG4bK-0e53sadfkasldkfj
Call-ID: 6076913b1c39c212@REVMTEpG
CSeq: 2 UPDATE
Contact: <sip:[email protected]>
Content-Type: application/sdp
Content-Length: xxxx
Supported: from-change
v=0
o=- 1181923068 1181923196 IN IP4 ua2.example.com
s=example1
c=IN IP4 ua2.example.com
a=setup:actpass
a=fingerprint: SHA-1 \
4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB
t=0 0
m=audio 6056 RTP/AVP 0
a=sendrecv
a=tcap:1 UDP/TLS/RTP/SAVP RTP/AVP
a=pcfg:1 t=1