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<p class="MsoNormal"><span lang="EN-US">Hi experts,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I’m working on the implementation for ‘2.4.6 Multiple REFER Requests in a Dialog’ of RFC3515 in a B2B SIP Proxy. Right now, I got stuck with two problems in the solution. Please see the paragraph from RFC- <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"> A REFER creates an implicit subscription sharing the dialog<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"> identifiers in the REFER request. If more than one REFER is issued<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"> in the same dialog (a second attempt at transferring a call for<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"> example), the dialog identifiers do not provide enough information to<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"> associate the resulting NOTIFYs with the proper REFER.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"> Thus, for the second and subsequent REFER requests a UA receives in a<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"> given dialog, it MUST include an id parameter[2] in the Event header<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"> field of each NOTIFY containing the sequence number (the number from<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"> the CSeq header field value) of the REFER this NOTIFY is associated<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"> with. This id parameter MAY be included in NOTIFYs to the first<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"> REFER a UA receives in a given dialog. A SUBSCRIBE sent to refresh<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-CA"> or terminate this subscription MUST contain this id parameter.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Different from the definition in RFC, the NOTIFY forwarded by the proxy contains the same Id in Event header as the other side. Please see the below chart –<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> B2BProxy<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> |
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> <- REFER 2 (Cseq=2) | <-REFER 1 (Cseq=1003)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> . . . | . . .<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">->NOTIFY 1 (event:<b>id=2</b>) | ->NOTIFY 2 (<u>event<b>:id=2</b>)</u><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The current problem is, the above NOTIFY on the right side should
<u>include ‘id=1003’ instead of ‘id=2’</u>.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The solution I’m trying is as in the following flow –<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> 1. get CSeq 1 of REFER 1 in route[b2b_request]{} -><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> 2. get CSeq 2 of REFER 2 in local_route{}, then save the pair(key=CSeq2, value=CSeq1) in a map set-><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> 3. get Id from NOTIFY 1 event in route[b2b_request]{} -><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> 4. use Id as key then get matched CSeq1 from the map set, use remove_hf() and append_hf() to modify the event header in local_route{}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">My two questions are:<o:p></o:p></span></p>
<ol style="margin-top:0cm" start="1" type="1">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l1 level1 lfo2"><span lang="EN-US">To transfer Cseq 1 from step1 to step2, I tried a variable in the AVP type but it didn’t work. The script variable can work but it doesn’t fit because the processing
is based on per request. Can I ask if you have any suggest on how to transfer the value from route[b2b_request]{} to local_route{}? <o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l1 level1 lfo2"><span lang="EN-US">In the step2, I tried to create and operate a JSON map set to save the CSeq pairs. But the JSON data didn’t work for me.<o:p></o:p></span></li></ol>
<p class="MsoListParagraph"><span lang="EN-US"> My source : <o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US"> $json(csList) = ””; # Initialize the data set, not sure if it’s correct<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US"> $json(csList/”$cs”) = “$avp(csNum)”;<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US"> The error I got:<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US"> ERROR:core:do_assign: setting PV failed<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US"> ERROR:core:do_assign: error at /usr/local//et/opensips/opensips.cfg:531<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thank you very much for the help! Any your suggests are very welcomed.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Li<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p></o:p></span></p>
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