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

Hi,Charles:
I agree we should discuss how to fix these issues on XRBLOCK list. Below is my proposed changes and input.
Some of my proposed changes have already been posted to IESG mailing list.

Regards!
-Qin
----- Original Message ----- 
From: "Charles Eckel (eckelcu)" <eckelcu@cisco.com>
To: <xrblock@ietf.org>
Sent: Wednesday, July 04, 2012 3:59 AM
Subject: [xrblock] IESG evaluation comments for draft-ietf-xrblock-rtcp-xr-meas-identity-07

> 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.

[Qin]: Agree to omit it altogether rather than set the lenght field to 0 since early APSI is one metric carried in the measurement information now it is separated out and carried using one new SDES item.
My proposed change in IESG also is to delete the last sentence " If no identifier is provided, the length field
MUST be set to zero." from the section 3.1.

> 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.

[Qin]: Agree, we should not limit the cumulative duration to less than 18.2 hours. The proposal looks good to me.
Here is my input to fix this issue:
OLD TEXT:
"
      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]. 

"
NEW TEXT:
"
      Measurement Duration (Cumulative) : 64 bits
      The duration of the reporting interval applicable to Cumulative reports which use this
      Measurement Information block.  The value of this field is represented using a 64-bit 
      NTP-format timestamp as defined in [RFC5905], which is 64-bit unsigned fixed-point
      number with the integer part in the first 32 bits and the fractional part  in the last 32 bits. 
      It 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]. 

"

> Comments on both of these issues would be greatly appreciated.
> 
> Cheers,
> Charles
> 
> 
> 
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