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SBC drill with the cited answer

B2BUA, where PSTN SIP lands, the trusted list, and Teams TLS, answered in the body.

Learn in 5 minutes

  1. Call an SBC a B2BUA with RFC 7092
  2. Land PSTN SIP on CUBE or CUCM
  3. Separate IOS trusted-list checks from SIP RFCs

Visual

Two legs, two Call-IDs possible · study drawing · cyphermonkeylabs.com AliceCUBECarrier INVITE 100 INVITE 200 200

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Product pages and RFCs stay in different sentences.

Worked example

Count the legs How do you match the carrier 200 to the caller's ACK?

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

Fault

The carrier leg uses a new Call-ID. The ticket says the SBC is broken because Record-Route is absent, and it moves the carrier trunk onto UCCX in the same edit.

A B2BUA terminates one dialog and opens another. UCCX does not take the carrier trunk.

Quiz

An SBC is commonly


A B2BUA Call-ID


PSTN SIP lands on


The trusted list is


Teams TLS in this answer is


Teams 403 in this answer means


Ecosystem

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

E911 / emergency calling Location has to ride with the call. RFC 6881 is the BCP, RFC 6442 carries location in SIP, and the FCC MLTS page states Kari’s Law and RAY BAUM’s Act obligations for multi-line systems.

Glossary · Ecosystem map · Ports · Troubleshooting

Sources and go deeper