Subject: [xrblock] Tags and SSRC's in XR Blocks

From: Alan Clark <[email-masked]>
Date: Tue, 15 Nov 2011 22:27:08 -0500

The original concept for the XR blocks used the idea of a Tag to relate the
metrics blocks to a measurement identification block.  This approach was
used for a number of reasons:

(i) It is more efficient as the Source SSRC, which is already in the
measurement identification block, does not have to be repeated for every
metrics block.  As some of the metrics blocks are only 3-4 words in size,
the redundant SSRC increases the message size by 25-30%.

(ii) It provides more flexibility in the organization of metrics blocks into
RTCP packets - allowing either one RTCP packet to contain several sets of
measurement data or allowing one set of measurement data to be carried over
several RTCP packets.

I¹m not sure why the Tag was removed - was there some good technical reason
for this?

Alan

---

From: "Charles Eckel (eckelcu)" <[email-masked]>
Date: Thu, 17 Nov 2011 20:57:14 -0800

Hi Alan,

As this issue concerns the monarch draft as well as the measurement
identification block draft, it was discussed on both the avtcore and
xrblock lists:

http://proxy2974.my-addr.net/myaddrproxy.php/http/www.ietf.org/mail-arch
ive/web/avt/current/msg14582.html
and
http://proxy2974.my-addr.net/myaddrproxy.php/http/www.ietf.org/mail-arch
ive/web/avt/current/msg14658.html

The decision at that time was to remove the tag and rely on the SSRC.
The thread speaks to point (i) you raised. It does not speak to point
(ii).
Point (ii) was raised during the xrblock working group session with
week, and one of the action items for the measurement identification
draft was to clarify the intended usage of the measurement identity
block in such cases.

Cheers,
Charles

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On
Behalf Of Alan Clark
> Sent: Wednesday, November 16, 2011 11:27 AM
> To: [email-masked]
> Subject: [xrblock] Tags and SSRC's in XR Blocks
> 
> 
> The original concept for the XR blocks used the idea of a Tag to
relate the metrics blocks to a
> measurement identification block.  This approach was used for a number
> (i) It is more efficient as the Source SSRC, which is already in the
measurement identification block,
> does not have to be repeated for every metrics block.  As some of the
metrics blocks are only 3-4
> words in size, the redundant SSRC increases the message size by
25-30%.
> 
> (ii) It provides more flexibility in the organization of metrics
blocks into RTCP packets - allowing
> either one RTCP packet to contain several sets of measurement data or
allowing one set of measurement
> data to be carried over several RTCP packets.
> 
> I'm not sure why the Tag was removed - was there some good technical
reason for this?

---

From: Varun Singh <[email-masked]>
Date: Fri, 18 Nov 2011 18:24:07 +0800

Hi Alan,

draft-clark-xrblock-rtcp-xr-qoe-00 has a 6-bit tag while the Measurement ID
block defines it as a 3-bit identifier.

In draft-ietf-avt-rtcp-xr-meas-identity-02#section-2: there is a 0 bit, is
this done so that the Tag field aligns across blocks? if so then there
should be 2 zero bits to cover for the new I field.

Also in the measurement identity draft:

Bits shown as '0' in the figure SHOULD be set to zero.

SHOULD be MUST?

Cheers,

Varun

On Fri, Nov 18, 2011 at 12:57, Charles Eckel (eckelcu) <[email-masked]>wrote:

> _______________________________________________
> xrblock mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/xrblock
>

-- 
http://www.netlab.tkk.fi/~varun/

---

From: Varun Singh <[email-masked]>
Date: Mon, 21 Nov 2011 13:34:49 +0200

Hi Alan,

in draft-clark-xrblock-rtcp-xr-qoe-00:

Numerical values for interval or duration are provided in the
      Measurement Identifier block referenced by the tag field below.

Is the measurement identifier block only used for sample duration. Interval
and cumulative measurements don't require the tag field. Is the Tag set to
0 in these cases?

On Fri, Nov 18, 2011 at 12:24, Varun Singh <[email-masked]> wrote:

> Hi Alan,
>
> draft-clark-xrblock-rtcp-xr-qoe-00 has a 6-bit tag while the Measurement
> ID block defines it as a 3-bit identifier.
>
>> ive/web/avt/current/msg14582.html<http://proxy2974.my-addr.net/myaddrproxy.php/http/www.ietf.org/mail-archive/web/avt/current/msg14582.html>
>> and
>> ive/web/avt/current/msg14658.html<http://proxy2974.my-addr.net/myaddrproxy.php/http/www.ietf.org/mail-archive/web/avt/current/msg14658.html>
>>

---

From: Qin Wu <[email-masked]>
Date: Tue, 22 Nov 2011 20:14:55 +0800

Hi,
----- Original Message ----- 
From: "Charles Eckel (eckelcu)" <[email-masked]>
To: "Alan Clark" <[email-masked]>; <[email-masked]>
Sent: Friday, November 18, 2011 12:57 PM
Subject: Re: [xrblock] Tags and SSRC's in XR Blocks

> The thread speaks to point (i) you raised. 

[Qin] Yes, all the XR Block works  in progress or been published follows
one common rule, i.e., use SSRC of packet sender field in the XR packet to indicate
who is the sender of XR packet, use SSRC of media source field in the Report Block 
to indicate which RTP stream is associated with this Report Block.  These XR Block
works include RFC3611, RFC6332, RFC5725, draft-ietf-avtcore-ecn-for-rtp.
Also the RTCP extension follow the similar rule.

>It does not speak to point
> (ii).

[Qin]: Using SSRC in each Report Block and Measurement Information Block 
also allow such flexibility. i.e., if measurement data for the same interval span over
more than one RTCP packet, we can choose to carry measurement data in multiple 
RTCP packets.

One potential issue to use tag is we don't have way to check tag value collision 
when measurement data are carried in multiple RTCP packets. But using SSRC don't
have such issue since SSRC should be unique within one RTP session.