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OPTIONS keepalives

SBCs probe a peer with OPTIONS. A 200 OK means the peer answered. The interval is product configuration.

Learn in 5 minutes

  1. Build a legal OPTIONS
  2. Read a 200 OK as liveness
  3. Keep the timer out of the RFC

Visual

OPTIONS before the next INVITE · study drawing · cyphermonkeylabs.com SBCCarrier OPTIONS 200 INVITE 100

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RFC 3261 defines OPTIONS. It does not define the SBC’s repeat timer.

Worked example

Check the OPTIONS CSeq Dissect this keepalive. What is the CSeq method?

    Fault

    A peer ignores the keepalive. The request line says OPTIONS and the CSeq says INVITE.

    RFC 3261 requires the CSeq method to match the request.

    Quiz

    A keepalive OPTIONS uses CSeq method


    200 OK to OPTIONS means


    The repeat interval for SBC OPTIONS is


    OPTIONS is defined in


    The INVITE after a keepalive is


    Allow on the 200 OK


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