[xrblock] IESG evaluation comments for draft-ietf-xrblock-rtcp-xr-meas-identity-07

["Charles Eckel (eckelcu)" <[e-mail]>]

During IESG evaluation of the draft, two issues have been raised that, as document shepherd, I feel require additional input from the working group.
First, section 3.1 of the draft currently reads follows:

   3.1. APSI: Application Specific Identifier SDES Item
   Application specific identifier is an additional identifier which is
   useful in the context of a specific application, e.g. an MPEG-2
   transport identifier [MPEG2].  This item MUST be ignored by
   applications that are not configured to make use of it.  The
   identifier is variable length.  Its length is described by the length
   field.  The value of the length field does not include the two octet
   SDES item header.  If no identifier is provided, the length field
   MUST be set to zero.

The question is, why set the length field to 0 instead of omitting the SDES item entirely? As the APSI identifier is the only piece information conveyed by this SDES item, it seems more appropriate to omit it altogether. If there is a good reason to do otherwise, an explanation of that  reason should be added as justification.

Second, the cumulative duration is defined in section 4.1 as follows:

   Measurement Duration (Cumulative) : 32 bits
      The duration, expressed in units of 1/65536 seconds, of the
      reporting interval applicable to Cumulative reports which use this
      Measurement Information block.  The value of this field can be
      calculated by the receiver of the RTP media stream, for example,
      based on received RTP media packets or using RTCP method described
      in [RFC3550]. 

The units for the measurement was changed from millisecond to 1/65536 based on working group input. A side effect of this however, is that the maximum cumulative duration that can be expressed is 18.2 hours. This does not seem sufficient, as the cumulative duration may be up to the length of the RTP session. The proposal is to increase the field from 32 bits to 64 bits.

Comments on both of these issues would be greatly appreciated.

Cheers,
Charles