|
Written by Hemanshu Patel
|
|
Thursday, 08 November 2007 |
|
Page 8 of 17 3.2. Session Establishment Through Two Proxies
Alice Proxy 1 Proxy 2 Bob
| | | |
| INVITE F1 | | |
|--------------->| | |
| 407 F2 | | |
|<---------------| | |
| ACK F3 | | |
|--------------->| | |
| INVITE F4 | | |
|--------------->| INVITE F5 | |
| 100 F6 |--------------->| INVITE F7 |
|<---------------| 100 F8 |--------------->|
| |<---------------| |
| | | 180 F9 |
| | 180 F10 |<---------------|
| 180 F11 |<---------------| |
|<---------------| | 200 F12 |
| | 200 F13 |<---------------|
| 200 F14 |<---------------| |
|<---------------| | |
| ACK F15 | | |
|--------------->| ACK F16 | |
| |--------------->| ACK F17 |
| | |--------------->|
| Both Way RTP Media |
|<================================================>|
| | | BYE F18 |
| | BYE F19 |<---------------|
| BYE F20 |<---------------| |
|<---------------| | |
| 200 F21 | | |
|--------------->| 200 F22 | |
| |--------------->| 200 F23 |
| | |--------------->|
| | | |
In this scenario, Alice completes a call to Bob using two proxies
Proxy 1 and Proxy 2. The initial INVITE (F1) contains a pre-loaded
Route header with the address of Proxy 1 (Proxy 1 is configured as a
default outbound proxy for Alice). The request does not contain the
Authorization credentials Proxy 1 requires, so a 407 Proxy
Authorization response is sent containing the challenge information.
A new INVITE (F4) is then sent containing the correct credentials and
the call proceeds. The call terminates when Bob disconnects by
initiating a BYE message.
Proxy 1 inserts a Record-Route header into the INVITE message to
ensure that it is present in all subsequent message exchanges. Proxy
2 also inserts itself into the Record-Route header. The ACK (F15)
and BYE (F18) both have a Route header.
Message Details
F1 INVITE Alice -> Proxy 1
INVITE sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
SIP/2.0
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74b43
Max-Forwards: 70
Route: <sip:ss1.atlanta.example.com;lr>
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 1 INVITE
Contact: <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
;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
/* Proxy 1 challenges Alice for authentication */
F2 407 Proxy Authorization Required Proxy 1 -> Alice
SIP/2.0 407 Proxy Authorization Required
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74b43
;received=192.0.2.101
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=3flal12sf
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 1 INVITE
Proxy-Authenticate: Digest realm="atlanta.example.com", qop="auth",
nonce="f84f1cec41e6cbe5aea9c8e88d359",
opaque="", stale=FALSE, algorithm=MD5
Content-Length: 0
F3 ACK Alice -> Proxy 1
ACK sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
SIP/2.0
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74b43
Max-Forwards: 70
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=3flal12sf
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 1 ACK
Content-Length: 0
/* Alice responds be re-sending the INVITE with authentication
credentials in it. */
F4 INVITE Alice -> Proxy 1
INVITE sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
SIP/2.0
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
Route: <sip:ss1.atlanta.example.com;lr>
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 2 INVITE
Contact: <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
;transport=tcp>
Proxy-Authorization: Digest username="alice",
realm="atlanta.example.com",
nonce="wf84f1ceczx41ae6cbe5aea9c8e88d359", opaque="",
uri="sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
",
response="42ce3cef44b22f50c6a6071bc8"
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
/* Proxy 1 accepts the credentials and forwards the INVITE to Proxy
2. Client for Alice prepares to receive data on port 49172 from the
network. */
F5 INVITE Proxy 1 -> Proxy 2
INVITE sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
SIP/2.0
Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 69
Record-Route: <sip:ss1.atlanta.example.com;lr>
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 2 INVITE
Contact: <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
;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
F6 100 Trying Proxy 1 -> Alice
SIP/2.0 100 Trying
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 2 INVITE
Content-Length: 0
F7 INVITE Proxy 2 -> Bob
INVITE sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
SIP/2.0
Via: SIP/2.0/TCP ss2.biloxi.example.com:5060;branch=z9hG4bK721e4.1
Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 68
Record-Route: <sip:ss2.biloxi.example.com;lr>,
<sip:ss1.atlanta.example.com;lr>
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 2 INVITE
Contact: <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
;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
F8 100 Trying Proxy 2 -> Proxy 1
SIP/2.0 100 Trying
Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 2 INVITE
Content-Length: 0
F9 180 Ringing Bob -> Proxy 2
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP ss2.biloxi.example.com:5060;branch=z9hG4bK721e4.1
;received=192.0.2.222
Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.example.com;lr>,
<sip:ss1.atlanta.example.com;lr>
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
Contact: <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
;transport=tcp>
CSeq: 2 INVITE
Content-Length: 0
F10 180 Ringing Proxy 2 -> Proxy 1
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.example.com;lr>,
<sip:ss1.atlanta.example.com;lr>
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
Contact: <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
;transport=tcp>
CSeq: 2 INVITE
Content-Length: 0
F11 180 Ringing Proxy 1 -> Alice
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.example.com;lr>,
<sip:ss1.atlanta.example.com;lr>
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
Contact: <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
;transport=tcp>
CSeq: 2 INVITE
Content-Length: 0
F12 200 OK Bob -> Proxy 2
SIP/2.0 200 OK
Via: SIP/2.0/TCP ss2.biloxi.example.com:5060;branch=z9hG4bK721e4.1
;received=192.0.2.222
Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.example.com;lr>,
<sip:ss1.atlanta.example.com;lr>
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 2 INVITE
Contact: <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
;transport=tcp>
Content-Type: application/sdp
Content-Length: 147
v=0
o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F13 200 OK Proxy 2 -> Proxy 1
SIP/2.0 200 OK
Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.example.com;lr>,
<sip:ss1.atlanta.example.com;lr>
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 2 INVITE
Contact: <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
;transport=tcp>
Content-Type: application/sdp
Content-Length: 147
v=0
o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F14 200 OK Proxy 1 -> Alice
SIP/2.0 200 OK
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.example.com;lr>,
<sip:ss1.atlanta.example.com;lr>
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 2 INVITE
Contact: <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
;transport=tcp>
Content-Type: application/sdp
Content-Length: 147
v=0
o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F15 ACK Alice -> Proxy 1
ACK sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
SIP/2.0
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74b76
Max-Forwards: 70
Route: <sip:ss1.atlanta.example.com;lr>,
<sip:ss2.biloxi.example.com;lr>
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 2 ACK
Content-Length: 0
F16 ACK Proxy 1 -> Proxy 2
ACK sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
SIP/2.0
Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74b76
;received=192.0.2.101
Max-Forwards: 69
Route: <sip:ss2.biloxi.example.com;lr>
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 2 ACK
Content-Length: 0
F17 ACK Proxy 2 -> Bob
ACK sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
SIP/2.0
Via: SIP/2.0/TCP ss2.biloxi.example.com:5060;branch=z9hG4bK721e4.1
Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74b76
;received=192.0.2.101
Max-Forwards: 68
From: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
To: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 2 ACK
Content-Length: 0
/* RTP streams are established between Alice and Bob */
/* Bob Hangs Up with Alice. */
/* Again, note that the CSeq is NOT 3. Alice and Bob maintain
their own separate CSeq counts */
F18 BYE Bob -> Proxy 2
BYE sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
SIP/2.0
Via: SIP/2.0/TCP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
Max-Forwards: 70
Route: <sip:ss2.biloxi.example.com;lr>,
<sip:ss1.atlanta.example.com;lr>
From: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
To: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 1 BYE
Content-Length: 0
F19 BYE Proxy 2 -> Proxy 1
BYE sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
SIP/2.0
Via: SIP/2.0/TCP ss2.biloxi.example.com:5060;branch=z9hG4bK721e4.1
Via: SIP/2.0/TCP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.201
Max-Forwards: 69
Route: <sip:ss1.atlanta.example.com;lr>
From: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
To: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 1 BYE
Content-Length: 0
F20 BYE Proxy 1 -> Alice
BYE sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
SIP/2.0
Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1
Via: SIP/2.0/TCP ss2.biloxi.example.com:5060;branch=z9hG4bK721e4.1
;received=192.0.2.222
Via: SIP/2.0/TCP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.201
Max-Forwards: 68
From: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
To: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 1 BYE
Content-Length: 0
F21 200 OK Alice -> Proxy 1
SIP/2.0 200 OK
Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP ss2.biloxi.example.com:5060;branch=z9hG4bK721e4.1
;received=192.0.2.222
Via: SIP/2.0/TCP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.201
From: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
To: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 1 BYE
Content-Length: 0
F22 200 OK Proxy 1 -> Proxy 2
SIP/2.0 200 OK
Via: SIP/2.0/TCP ss2.biloxi.example.com:5060;branch=z9hG4bK721e4.1
;received=192.0.2.222
Via: SIP/2.0/TCP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.101
From: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
To: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 1 BYE
Content-Length: 0
F23 200 OK Proxy 2 -> Bob
SIP/2.0 200 OK
Via: SIP/2.0/TCP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.201
From: Bob <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=314159
To: Alice <sip:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
>;tag=9fxced76sl
Call-ID:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
CSeq: 1 BYE
Content-Length: 0
|
|
| |
|
|
