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Direction attributes and hold

sendrecv, sendonly, recvonly, and inactive are per stream. Hold is commonly sendonly or inactive.

Learn in 5 minutes

  1. List the four direction attributes
  2. Answer sendonly with recvonly or inactive
  3. Place a call on hold without c=0.0.0.0

Visual

re-INVITE to sendonly · study drawing · cyphermonkeylabs.com AliceSBC INVITE 200 re-INVITE 200

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The answer direction is from the answerer. Hold offers are commonly sendonly or inactive.

Worked example

Answer a hold The offer is sendonly. A legal answer is recvonly. Negotiate and read the direction line.

  1. Press Negotiate.
  2. Read the offer direction.
  3. Read the answer direction.

Fault

Music-on-hold re-INVITE sets the connection address to 0.0.0.0 and leaves a=sendrecv. The peer keeps the old media or drops RTCP.

RFC 3264 uses direction attributes for hold. The zero address is the retired behavior.

Quiz

A sendonly offer may be answered with


Hold is commonly


c=IN IP4 0.0.0.0 for hold is


An inactive offer is answered with


A media-level direction attribute


recvonly means the agent will


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