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Same m-lines, same order

RFC 3264 matches streams by position. The answer has the same number of m-lines, in the same order.

Learn in 5 minutes

  1. Count m-lines in the offer and in the answer
  2. Reject a stream without deleting its position
  3. Keep later offers in the same order

Visual

Two streams, one refused · study drawing · cyphermonkeylabs.com AliceSBC INVITE 100 180 200

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Stream 1 stays stream 1. A rejected second stream is still the second m-line.

Worked example

Negotiate two m-lines Run the negotiator. The answer refuses the second stream without deleting it.

  1. Press Negotiate.
  2. Confirm both m-lines are present.
  3. Read the second port.

Fault

The offer had two m-lines. The answer body has only the PCMU line, and the call fails.

RFC 3264 requires the same number of m-lines in the same order. A missing line is not a clean refusal.

Quiz

An answer to a two-m-line offer must contain


Swapping the two m-lines in the answer


Port 0 on an answer m-line means


RFC 6337 is


A format list on a port-0 line


The offer in the lab has which order?


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.

Glossary · Ecosystem map · Ports · Troubleshooting

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