Re: [xrblock] 2nd WGLC for draft-ietf-xrblock-rtcp-xr-qoe

Hi,Colin:
Thank for your valuable comments, see my reply inline below.

Regards!
-Qin

-----Original Message-----
From: xrblock-bounces@ietf.org [mailto:xrblock-bounces@ietf.org] On Behalf Of Colin Perkins
Sent: Tuesday, August 27, 2013 4:35 AM
To: Romascanu, Dan (Dan)
Cc: xrblock@ietf.org
Subject: Re: [xrblock] 2nd WGLC for draft-ietf-xrblock-rtcp-xr-qoe

On 21 Aug 2013, at 14:35, "Romascanu, Dan (Dan)" <dromasca@avaya.com> wrote:
> This is the second WGLC for the Internet-Draft 'RTP Control Protocol (RTCP) Extended Report (XR) Blocks for MoS Metric Reporting' previously known as 'RTP Control Protocol (RTCP) Extended Report (XR) Blocks for QoE Metric Reporting'. Please send your comments, questions, and concerns to the WG list before Wednesday 9/4. If you have no comments or questions and you believe that this document is ready for submission to the IESG for consideration as a Proposed Standard, please send a message stating this. 
> 
> The latest version of the document can be retrieved from http://www.ietf.org/id/draft-ietf-xrblock-rtcp-xr-qoe-10.txt.

The first paragraph of Section 3.1 talks about various flag bits in the header indicating which fields are present. However, the header doesn't appear to contain any such flags.

[Qin]: Good catch, I propose to remove the 1st useless paragraph that describes various flag bits as follows:
OLD TEXT:
"
3.1.  Metric Block Structure

   The report block contents are dependent upon a series of flag bits
   carried in the first part of the header.  Not all parameters need to
   be reported in each block.  Flags indicate which are and which are
   not reported. The fields corresponding to unreported parameters MUST
   be present, and MUST be set to zero.  The receiver MUST ignore any
   MoS Metrics Block with a non-zero value in any field flagged as
   unreported.  The encoding of MoS Metrics block payload consists of a
   series of 32 bit units called segments that describe payload Type,
   MoS algorithm and MoS value.

   The MoS Metrics Block has the following format:
"
NEW TEXT:
"
3.1.  Metric Block Structure

   The MoS Metrics Block has the following format:
"

The header described in Section 3.2 includes an Interval Metric Flag. I understand how MOS scores can be calculated for an interval, and perhaps how they could be sampled, but not how a cumulative MOS can be measured. Should cumulative, and possibly sampled, metrics be prohibited?

[Qin]: I agree that MoS metrics can only be measured at each interval duration, and can not be sampled. Also it doesn't look reasonable to report the Mos value in cumulative fashion, therefore I propose the following change:
OLD TEXT:
"
In this document, the value I=00 is reserved for future use.
Senders MUST NOT use the values I=00.  If a block is received with
I=00, the receiver MUST discard the block.

"
NEW TEXT:
"
In this document, MoS Metrics can only be measured at
each interval duration, and cannot be sampled or cumulated. 
Also the value I=00 is reserved for future use.
Senders MUST NOT use the values I=00 or I=01 or I=11.  
If a block is received with
I=00 or I=01 or I=11, the receiver MUST discard the block.
"

Should Section 3.2.1 be titled "Single channel..." rather than "Single stream..."?

[Qin]: looks good to me.

Section 3.2.1 says "For RTP sessions where multiple payload formats can be negotiated or the payload format changes during the mid-session), the value of this field will be used to indicate what payload format was in use for the reporting interval", but doesn't the payload type indicate this whether or not multiple payload formats are used in the session?

[Qin]:Yes it indicates multiple payload format can be used in one RTP session or in RTP sessions. 
So I propose the following change:
OLD TEXT:
"
MoS Metrics reporting depends on the payload format in use.  This
field identifies the format of the RTP payload.  For RTP session
where multiple payload formats can be negotiated or the payload
format changes during the mid-session), the value of this field
will be used to indicate what payload format was in use for the
reporting interval.
"
NEW TEXT:
"
MoS Metrics reporting depends on the payload format in use.  This
field identifies the format of the RTP payload.  For RTP session(s)
where multiple payload formats can be negotiated or the payload
format changes during the mid-session), the value of this field
will be used to indicate what payload format was in use for the
reporting interval.
"
Let me know if this addresses your comment.

-- 
Colin Perkins
http://csperkins.org/

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