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UPDATE before the INVITE completes

UPDATE can change the session while the initial INVITE is still outstanding, and it does not use the ACK rules.

Learn in 5 minutes

  1. Send UPDATE only when no offer is outstanding
  2. Treat UPDATE as a non-INVITE transaction
  3. Keep dialog identifiers stable across the session change

Visual

Answer the INVITE, then UPDATE · study drawing · cyphermonkeylabs.com UAPeer INVITE 183 PRACK 200 UPDATE 200

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The INVITE offer is answered in the 183. UPDATE is the next offer. The INVITE is still open.

Worked example

Negotiate the second offer The UPDATE offer adds a port change and still lists PCMU and PCMA. The answer keeps PCMU.

  1. Compare the m= lines.
  2. See which payload the answer kept.
  3. Note telephone-event on both sides.

Fault

The INVITE contains SDP. UPDATE with a new offer arrives before any answer. The UAS returns 491.

Offer/answer allows one outstanding offer. The INVITE offer has not been answered.

Quiz

UPDATE is defined in


A successful UPDATE is completed by


UPDATE may run before the INVITE 200 when


Call-ID and tags on UPDATE


Target refresh is specified in


The CSeq method token on the UPDATE is


Ecosystem

Glossary, sister systems, and the integration seam for this room.

Analytics Amazon Connect can attach conversational analytics to an external voice system with a SIPREC connector. The analytics plane is not a second SIP proxy for the customer call.

Glossary · Ecosystem map · Ports · Troubleshooting

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