[Dots] draft-ietf-dots-signal-channel-33: trigger-mitigation

["MeiLing Chen" <[e-mail]>]

Hi Tiru, Med;I read draft-ietf-dots-signal-channel-33, I have a question about the parameter of trigger-mitigation,

 trigger-mitigation:   If the parameter value is set to 'false', DDoS
      mitigation will not be triggered for the mitigation request unless
      the DOTS signal channel session is lost.
      If the DOTS client ceases to respond to heartbeat messages, the
      DOTS server can detect that the DOTS signal channel session is
      lost.  More details are discussed in Section 4.7.
Reddy, et al.           Expires November 11, 2019              [Page 18]
Internet-Draft        DOTS Signal Channel Protocol              May 2019
      The default value of the parameter is 'true' (that is, the
      mitigation starts immediately).  If 'trigger-mitigation' is not
      present in a request, this is equivalent to receiving a request
      with 'trigger-mitigation' set to 'true'.
question1: When send mitigation request first time, trigger-mitigation is set true; when session is lost, trigger-mitigation set false will work, so how to know session is lost?
question2: Why need this parameter and What was the initial requirements scenario?