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<p class="MsoNormal"><span style="color:black">Wrapping up on this one…<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">The SIP Stack error below occurred because CUCM (as the UAS) received an UPDATE request before receiving a PRACK for its 183 w/ answer. Possible solution is to have CUCM send a Require: 100rel in the 183 answer,
forcing the UAC to PRACK before sending the update, but the caveat in our scenario is that NRS v5.5 does not support PRACK.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">The UPDATE request from the NRS is sent during a blind transfer event. I guess another solution would be for the NRS to use REFER instead of UPDATE, but I cannot say whether or not this is possible from the Nortel
side. However, because the NRS doesn’t support sending PRACK, and CUCM is requiring PRACK before receiving an update (as per RFC 3311), it seems we’re stuck between a rock and a hard place unless it turns out the NRS can use REFER. The vendor supporting the
NRS is investigating this side of it further.<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>Relevant information<o:p></o:p></b></p>
<p class="MsoNormal"><span style="color:#404040"><a href="https://tools.ietf.org/html/rfc3311#section-5">https://tools.ietf.org/html/rfc3311#section-5</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#404040"><a href="https://tools.ietf.org/html/rfc3262#section-3">https://tools.ietf.org/html/rfc3262#section-3</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#404040"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="color:black">While on the topic of documentation, and please correct me if I’m mistaken, but I think the following Cisco doc should be updated:<o:p></o:p></span></b></p>
<p class="MsoPlainText" style="background:#C4BC96"><b>SIP Profile – 1xxRel<o:p></o:p></b></p>
<p class="MsoNormal" style="background:#C4BC96"><b><i><span style="color:#404040">“Note: Even if you make the above change, CUCM can support reliable responses only by sending PRACK as a UAC; however, for now,
</span></i></b><b><i><span style="color:red">it cannot send 180/183 with the Require: 100rel header as a UAS</span></i></b><b><i><span style="color:#404040">.”
</span></i></b><span style="font-size:12.0pt;color:#404040"> </span><span style="color:#404040"><a href="http://www.cisco.com/image/gif/paws/116086/116086-configure-cube-cucm-sip-00.pdf">http://www.cisco.com/image/gif/paws/116086/116086-configure-cube-cucm-sip-00.pdf</a><b><i><o:p></o:p></i></b></span></p>
<p class="MsoNormal"><span style="color:#404040"><o:p> </o:p></span></p>
<p class="MsoNormal">A more accurate statement would be that CUCM can send a Require: 100rel header and option as a UAS only when meeting the following prerequisites:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l0 level1 lfo3">
<![if !supportLists]><b><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman"">
</span></span></b><![endif]>First receiving 100rel in either the Supported: or Require: headers within the INVITE from the UAC<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:1.0in;text-indent:.5in"><b>| and |<o:p></o:p></b></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l0 level1 lfo3">
<![if !supportLists]><b><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman"">
</span></span></b><![endif]>Enabling Rel1XX Option on the SIP Profile to “Send PRACK for all 1xx Messages”.
<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in">Setting this option to “Send PRACK if 1xx Contains SDP” will not force CUCM to send a reliable provisional response to the UAC.<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:1.5in"><b>| or |<o:p></o:p></b></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l0 level1 lfo3">
<![if !supportLists]><b><span style="mso-list:Ignore">3.<span style="font:7.0pt "Times New Roman"">
</span></span></b><![endif]>Adding a SIP normalization script that inserts the Require header with 100rel option (UAC must support it)<o:p></o:p></p>
<p class="MsoNormal"><span style="color:#404040"><o:p> </o:p></span></p>
<p class="MsoNormal">Thank you for helping out on this earlier, Brian.<o:p></o:p></p>
<p class="MsoNormal"><span style="color:#404040"><o:p> </o:p></span></p>
<p class="MsoNormal">- Daniel<o:p></o:p></p>
<p class="MsoNormal"><span style="color:#404040"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b>From:</b> cisco-voip [mailto:cisco-voip-bounces@puck.nether.net]
<b>On Behalf Of </b>Daniel Pagan<br>
<b>Sent:</b> Thursday, February 13, 2014 6:16 PM<br>
<b>To:</b> Brian Meade (brmeade); cisco-voip@puck.nether.net<br>
<b>Subject:</b> Re: [cisco-voip] SIP Stack & Trace Question<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Brian:<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Thanks for the response.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">I’d have to review traces for a non-transfer scenario but it’s my understanding that, in this scenario, the 183 w/SDP from CUCM was the answer in the offer/answer model – the offer being Nortel’s INVITE w/SDP. Just after allocation of the
MTP, SIP Interface shows “SIPInterface-(292194)::handleOutgoingSDPAnswer”, which, correct me if I’m wrong, should complete the offer/answer:<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">INVITE (SDP offer) <span style="font-family:Wingdings">
à</span> CUCM<o:p></o:p></p>
<p class="MsoNormal">100 Trying <span style="font-family:Wingdings">
ß</span> <o:p></o:p></p>
<div>
<p class="MsoNormal"><span style="color:black">183 (SDP answer) </span>
<span style="font-family:Wingdings;color:black">ß</span><span style="color:black">
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:black">183 (No SDP)</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:black">UPDATE (SDP) </span>
<span style="font-family:Wingdings;color:black">à</span><span style="color:black">
</span><o:p></o:p></p>
</div>
<p class="MsoNormal"><b><span style="font-size:10.0pt">==</span></b><b><span style="font-size:10.0pt;font-family:"Courier New"">
<span style="color:red">SIP/Stack/Error/0x0/Last Offer not answered yet</span></span></b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt">== Note: Context ID (ccb=<id>) matches the ID created at the start of the dialogue</span></b><o:p></o:p></p>
<p class="MsoNormal">500 Internal SvrErr <span style="font-family:Wingdings">
ß</span> <o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal">Thoughts? Thanks again Brian.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">- Daniel<o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<div>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Brian Meade (brmeade) [<a href="mailto:brmeade@cisco.com">mailto:brmeade@cisco.com</a>]
<br>
<b>Sent:</b> Thursday, February 13, 2014 5:59 PM<br>
<b>To:</b> Daniel Pagan; <a href="mailto:cisco-voip@puck.nether.net">cisco-voip@puck.nether.net</a><br>
<b>Subject:</b> RE: SIP Stack & Trace Question</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Daniel,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">It seems to me like CUCM is waiting for an answer to the offer it sent in the 183 w/SDP. In a non-transfer scenario, does the Nortel side normally send a PRACK at that point? Possibly the Nortel side is sending
the Update before the PRACK?</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Thanks,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Brian</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<div>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> cisco-voip [<a href="mailto:cisco-voip-bounces@puck.nether.net">mailto:cisco-voip-bounces@puck.nether.net</a>]
<b>On Behalf Of </b>Daniel Pagan<br>
<b>Sent:</b> Thursday, February 13, 2014 5:08 PM<br>
<b>To:</b> <a href="mailto:cisco-voip@puck.nether.net">cisco-voip@puck.nether.net</a><br>
<b>Subject:</b> [cisco-voip] SIP Stack & Trace Question</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><b>Folks</b>:<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">I’m reviewing an issue and looking for some feedback on a specific SIP stack error. In a nutshell, what appears to be happening is CUCM (8.6.2.24090-1) responding to an UPDATE request with a 500 Internal Server Error in a very specific
transfer call flow:<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><b>.::: Call is established :::</b><o:p></o:p></p>
<p class="MsoNormal"><b>.::: Nortel Begins a xfer to CUCM :::</b><o:p></o:p></p>
<p class="MsoNormal"><b> </b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:12.0pt">Nortel ==== CUCM</span></b><o:p></o:p></p>
<p class="MsoNormal"><b>>>> INVITE w/SDP</b><o:p></o:p></p>
<p class="MsoNormal"><b> 100 Trying <<<</b><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4A452A">=======DA Successful</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4A452A">=======Outbound to ITSP</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4A452A">=======MTP Required on Rx SIP Trunk</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4A452A">=======MTP resource allocated</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4A452A">=======SDI trace events show </span>
<b><span style="font-size:10.0pt;color:#4A452A">SIPInterface-(292194)::handleOutgoing<u>SDPAnswer</u></span></b><span style="font-size:10.0pt;color:#4A452A">
</span><span style="color:#4A452A">once media info is collected for MTP</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><b> 183 w/ SDP </b><b><span style="font-size:9.0pt">(for MTP)</span> <<<</b><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4A452A">=====ITSP returns 183 w/ SDP</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><b> 183 <u>no</u> SDP <<<</b><o:p></o:p></p>
<p class="MsoNormal"><b>>>> UPDATE w/SDP</b><o:p></o:p></p>
<p class="MsoNormal"><b> </b><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4A452A">=====SIP stack detects an existing connection</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4A452A">=====SIP stack detects an SDP offer has yet to be answered</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><b> 500 Internal Svr Error <<<</b><o:p></o:p></p>
<p class="MsoNormal"><b> w/ retry-timer header</b><o:p></o:p></p>
<p class="MsoNormal"><b> ::: Call Xfer attempt fails :::</b><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">The SIP stack trace excerpt that raised a flag states<b>:</b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Courier New";color:red">SIP/Stack/Error/0x0/Last Offer not answered yet</span></b><o:p></o:p></p>
<p class="MsoNormal">This occurs after the UPDATE w/ SDP offer is received and immediately before the 500 response is generated.<o:p></o:p></p>
<p class="MsoNormal">SDI traces show the event was added to the UAS response table using same context ID created for the original INVITE.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">With this error in mind I decided to review the RFC for SIP UPDATE and found a very interesting piece of information:<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">“If an UPDATE is received that contains an offer, and the UAS has</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> generated an offer (in an UPDATE, PRACK or INVITE) to which it has</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> not yet received an answer, the UAS MUST reject the UPDATE with a 491</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> response.
</span><span style="font-size:10.0pt;font-family:"Courier New";color:#C00000">Similarly, if an UPDATE is received that contains an</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:#C00000"> offer, and the UAS has received an offer (in an UPDATE, PRACK, or</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:#C00000"> INVITE)
<u>to which it has not yet generated an answer</u>, the UAS MUST</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:#C00000"> reject the UPDATE with a 500 response, and MUST include a Retry-After</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:#C00000"> header field with a randomly chosen value between 0 and 10 seconds.”</span><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Courier New""> </span></b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Courier New""><a href="http://www.rfc-editor.org/rfc/rfc3311.txt">http://www.rfc-editor.org/rfc/rfc3311.txt</a></span></b><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">The 500 response to the UPDATE does indeed contain a Retry-After header. CUCM did generate an answer (see above) but SIP stack detects the last offer wasn’t answered. Although the Nortel PBX doesn’t reattempt after x seconds, a related
RFC states the UAC *may* reattempt but it’s not a requirement. With that said, I’m wondering if anyone can help answer a few questions:<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]><b><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman"">
</span></span></b><![endif]>Has anyone encountered this before?<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><![if !supportLists]><b><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman"">
</span></span></b><![endif]>Bug toolkit doesn’t return any good matches. Perhaps there’s an internal defect?<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><![if !supportLists]><b><span style="mso-list:Ignore">3.<span style="font:7.0pt "Times New Roman"">
</span></span></b><![endif]>The 2<sup>nd</sup> 183 from CUCM (with no SDP) contains a CSeq header for the original INVITE from Nortel.<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in">This is the most recent provisional from CUCM in response to the offer from Nortel.<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in">My initial thought is CUCM is referring back to this 2<sup>nd</sup> 183 when determining no answer was generated for the last offer. This would explain the 500 response w/ Retry-After header
<u>and</u> the SIP stack error stating that an answer has yet to be generated.<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in">:: Note: Call-ID headers are confirmed to be consistent throughout the SDI traces reviewed
<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in">:: Note: The Allow header contains UPDATE<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in">:: Note: CUBE is not involved in this call-flow<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><![if !supportLists]><b><span style="mso-list:Ignore">4.<span style="font:7.0pt "Times New Roman"">
</span></span></b><![endif]>Can anyone tell me what CCB is in the context of UAS response tables? Seeing quite a few “Adding to Response/Request Table” also piques my interest. Is there anything useful from a troubleshooting standpoint from these tables when
the ccb=<ID> is identified and marked in Notepad++?<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"> <o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in">Thoughts?<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Thanks ahead of time.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">- Daniel<o:p></o:p></p>
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