Last Call Review of draft-ietf-xrblock-rtcp-xr-loss-conceal-10
review-ietf-xrblock-rtcp-xr-loss-conceal-10-opsdir-lc-morton-2014-03-27-00

This is the OPS-DIR review of the subject draft.

I note that this draft was reviewed by Vinayak Hegde for the pm-dir;
he reviewed version 05 on May 31st, 2013.

I find no new operational issues extending RTCP-XR with this new block,
but have the following comments for clarity.

Al


   Interval Metric flag (I): 2 bit

      This field is used to indicate whether the Loss Concealment
      metrics are Sampled, Interval or Cumulative metrics:

         I=10: Interval Duration - the reported value applies to the
         most recent measurement interval duration between successive
         metrics reports.

         I=11: Cumulative Duration - the reported value applies to the
         accumulation period characteristic of cumulative measurements.

         I=01: Sampled Value - the reported value is a sampled
         instantaneous value.


      In this document, Loss Concealment Metrics can only be measured
      over definite intervals, and cannot be sampled.  Also, the value
      I=00 is reserved for future use.  Senders MUST NOT use the values
      I=00 or I=01.  If a block is received with I=00 or I=01, the
      receiver MUST discard the block.

Since I=01 is not allowed, remove it from the list and simply
retain the explanation that follows (like I=00 was omitted).
(the text above occurs twice in the draft)

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   SCS Threshold: 8 bits

      The SCS Threshold is defined as the percentage of packets
      corresponding to lost or discarded frames that must occur within a
      one second period in order for the second to be classified as a
      Severely Concealed Second.  This is expressed in numeric format
      0:8 and hence can represent a range of 0.1 to 25.5 percent loss or
      discard.

      A default threshold of 5% effective frame loss (50ms effective
      frame loss ) per second is suggested.

Please provide the value of the default threshold setting.

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