As explained in my last post showing the FusionPBX architecture, I am currently doing a training with some friends and before going to the wild command line, I am trying to explain information flows. In this article, I am trying to document a simple call flow. Please note that this diagram could vary if you compare with reality as dial-plans always vary from user to user. I have also taken out some SIP answers (in case a SIP purist read it)
When a call starts, regardless if it is an incoming call, outgoing call or internal call, it always follows the same basic processing. Leg A is who has started the call, Leg B is the target; not all the calls have two legs, calling to an IVR is an example of one-leg call. So, let us start with the call flow analysis.
INVITE sip:This email address is being protected from spambots. You need JavaScript enabled to view it.;user=phone SIP/2.0
v: SIP/2.0/UDP 192.168.7.230:3073;branch=z9hG4bK-syuwuao4azwr;rport
f: "LDLQ" <sip:This email address is being protected from spambots. You need JavaScript enabled to view it.;transport=tcp>;tag=ng04c3f006
t: <sip:This email address is being protected from spambots. You need JavaScript enabled to view it.;user=phone>
i: 9bbdbb5a1923-b8xknstp41e3
CSeq: 1 INVITE
Max-Forwards: 70
m: <sip:This email address is being protected from spambots. You need JavaScript enabled to view it.:3073;line=mvyrdokj>;reg-id=1
X-Serialnumber: 000413414375
P-Key-Flags: resolution="31x13", keys="4"
User-Agent: snom870/8.7.3.25
Accept: application/sdp
Allow: INVITE, ACK, CANCEL, BYE, REFER, OPTIONS, NOTIFY, SUBSCRIBE, PRACK, MESSAGE, INFO, UPDATE
Allow-Events: talk, hold, refer, call-info
Supported: 100rel, replaces, from-change
c: application/sdp
l: 293
v=0
o=root 1261059876 1261059876 IN IP4 192.168.7.230
s=call
c=IN IP4 192.168.7.230
t=0 0
m=audio 56460 RTP/AVP 18 0 8 101
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=ptime:20
a=sendrecv
SIP/2.0 407 Proxy Authentication Required
Via: SIP/2.0/UDP 192.168.7.230:3073;branch=z9hG4bK-syuwuao4azwr;rport=3073;received=65.110.221.7
From: "LDLQ" <sip:This email address is being protected from spambots. You need JavaScript enabled to view it.;transport=tcp>;tag=ng04c3f006
To: <sip:This email address is being protected from spambots. You need JavaScript enabled to view it.;user=phone>;tag=7HacvmgjZ6Zpc
Call-ID: 9bbdbb5a1923-b8xknstp41e3
CSeq: 1 INVITE
User-Agent: FreeSWITCH
Accept: application/sdp
Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLIC, SUBSCRIBE
Supported: timer, path, replaces
Allow-Events: talk, hold, conference, presence, as-feature-event, dialog, line-seize, call-info, sla, include-session-description, presence.winfo, message-summary, refer
Proxy-Authenticate: Digest realm="pbx.to-call.me", nonce="94604a51-f4eb-45f1-ba0a-4e116d84c8a9" algorithm=MD5, qop="auth"
Content-Length: 0
INVITE sip:This email address is being protected from spambots. You need JavaScript enabled to view it.;user=phone SIP/2.0
v: SIP/2.0/UDP 192.168.7.230:3073;branch=z9hG4bK-6b1qnxauwmq2;rport
f: "LDLQ" <sip:This email address is being protected from spambots. You need JavaScript enabled to view it.;transport=tcp>;tag=ng04c3f006
t: <sip:This email address is being protected from spambots. You need JavaScript enabled to view it.;user=phone>
i: 9bbdbb5a1923-b8xknstp41e3
CSeq: 2 INVITE
Max-Forwards: 70
m:
<sip:This email address is being protected from spambots. You need JavaScript enabled to view it.:3073;line=mvyrdokj>;reg-id=1
X-Serialnumber: 000413414375
P-Key-Flags: resolution="31x13", keys="4"
User-Agent: snom870/8.7.3.25
Accept: application/sdp
Allow: INVITE, ACK, CANCEL, BYE, REFER, OPTIONS, NOTIFY, SUBSCRIBE, PRACK, MESSAGE, INFO, UPDATE
Allow-Events: talk, hold, refer, call-info
Supported: 100rel, replaces, from-change
Proxy-Authorization: Digest username="daniel.lucio",realm="pbx.to-call.me",nonce="94604a51-f4eb-45f1-ba0a-4e116d84c8a9",uri="sip:This email address is being protected from spambots. You need JavaScript enabled to view it.;user=phone",qop=auth,nc=00000001,cnone="7936b0b1",response="1be4eba1bc250a0b69986bf634dbdcfe",algorithm=MD5
c: application/sdp
l: 293
v=0
o=root 1261059876 1261059876 IN IP4 192.168.7.230
s=call
c=IN IP4 192.168.7.230
t=0 0
m=audio 56460 RTP/AVP 18 0 8 101
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=ptime:20
a=sendrecv
SIP/2.0 200 OK
Via: SIP/2.0/UDP 192.168.7.230:3073;branch=z9hG4bK-6b1qnxauwmq2;rport=3073;received=65.110.221.7
From: "LDLQ" <sip:This email address is being protected from spambots. You need JavaScript enabled to view it.;transport=tcp>;tag=ng04c3f006
To: <sip:This email address is being protected from spambots. You need JavaScript enabled to view it.;user=phone>;tag=93vXZajSSrcvK
Call-ID: 9bbdbb5a1923-b8xknstp41e3
CSeq: 2 INVITE
Contact: <sip:This email address is being protected from spambots. You need JavaScript enabled to view it.:5060;transport=udp>
User-Agent: FreeSWITCH
Accept: application/sdp
Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLI, SUBSCRIBE
Supported: timer, path, replaces
Allow-Events: talk, hold, conference, presence, as-feature-event, dialog, line-seize, call-info, sla, include-session-description, presence.winfo, message-summary, refer
Session-Expires: 120;refresher=uas
Content-Type: application/sdp
Content-Disposition: session
Content-Length: 247
Remote-Party-ID: "16137371111" <sip:This email address is being protected from spambots. You need JavaScript enabled to view it.>;party=calling;privacy=off;scree=on
v=0
o=FreeSWITCH 1522221044 1522221045 IN IP4 198.23.164.220
s=FreeSWITCH
c=IN IP4 198.23.164.220
t=0 0
m=audio 32180 RTP/AVP 18 101
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=ptime:20
Note that this payload has the final decision about what codec and RTP ports the Leg A will interact with the FreeSWITCH daemon.
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