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Status codes you will actually see

Read provisional and final codes from RFC 3261 section 21, and keep 422 with RFC 4028.

Learn in 5 minutes

  1. Separate provisional codes from final ones
  2. Place 422 with the session-timer RFC
  3. Use 488 for this UA and 606 for a global refusal

Visual

CANCEL, then 487 · study drawing · cyphermonkeylabs.com AliceSBC INVITE 100 180 CANCEL 200 487 ACK

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422 is Session Interval Too Small from RFC 4028. The other rows are the RFC 3261 section 21 phrases this lesson teaches, plus 606.

Worked example

Name the 487 Step the ladder. Which response ends the INVITE, and which 200 belongs to the CANCEL?

  1. Press Play.
  2. Step until the hop named in the question.
  3. Inspect that message and answer the check.

Fault

A carrier answers Session-Expires: 90 with 422 and Min-SE: 1800. The ticket says RFC 3261 section 21 defines 422.

The reason phrase is Session Interval Too Small. The base section 21 list is the wrong citation.

Quiz

487 Request Terminated follows


422 Session Interval Too Small is defined in


488 compared with 606


401 differs from 407 because


183 Session Progress is


The ACK on this ladder's 487 is


Ecosystem

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

Quality management and recording QM scores interactions. The standardized way an SBC forks a session to a recorder is SIPREC.

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