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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Hello,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I’m trying to understand how the dispatcher module works and how the timers in the TM module influence the behavior.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>My architecture looks like this:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>UA1 ---- SBC1 ---- Kamailio ----- SBC2 ---- FreeSWITCH App Server(x2)<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>What I got so far:<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>1)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>UA1 sends an INVITE to SBC1, which bridges the call between the UA1 and Kamailio<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>2)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>INVITE is received by Kamailio.<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>3)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Kamailio looks in its dispatcher table to dispatch the INVITE to its destination<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>4)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Kamailio rewrites the $du value to that of the SBC2<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>5)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Kamailio rewrites the request-uri and sends the INVITE to the destination in $du.<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>6)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>SBC2 is a FreeSWITCH instance which bridges the call (does not answer). It only responds back with a 100 TRYING<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>7)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>SBC2 tries to contact the endpoint (FS App Server 1) in the request-uri, but the destination does not respond because it is unavailable. <o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>8)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Kamailio keeps waiting for a final reply.<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>9)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>The fr_inv_timer is set to 5000 on startup<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>10)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Once the timer hits, Kamailio executes the route set in t_failure_route<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>11)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>The failure route looks like this:<o:p></o:p></p><p class=MsoNormal style='text-indent:.5in'>if(t_is_expired()) { ... }<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal> if (t_is_canceled()) { ... }<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal> if(t_check_status("500") || t_branch_timeout() || !t_branch_replied()) {<o:p></o:p></p><p class=MsoNormal> ....<o:p></o:p></p><p class=MsoNormal> }<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>12)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Kamailio enters the third if block in which the next domain is selected and the $du is rewritten again to that of SBC2<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>13)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>A new INVITE is generated and sent to its destination (FS App Server 2) through SBC2. Nothing is sent back to SBC1 yet, because Kamailio handles the failover here.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Is this correct?<o:p></o:p></p><p class=MsoNormal>Are there any other timers which are fired which I missed, or does the fr_inv_timer have nothing to do with this?<o:p></o:p></p><p class=MsoNormal>If Kamailio is supposed to load balance between FS App Server 1 and 2 using the Round-Robin algorithm, does it in case of an unreachable first destination take the next destination in the route set?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Regards,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Grant<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>