Subject: [MMUSIC] TIAS Bandwidth in draft-ietf-mmusic-sdp-mux-attributes-10

From: Magnus Westerlund <[email-masked]>
Date: Fri, 11 Sep 2015 16:28:59 +0200

Hi,

I looked at Section 6.3 of draft-ietf-mmusic-sdp-mux-attributes-10 and 
reacted to the below text.

    NOTE: The intention of TIAS is that the media level bit-rate is
    multiplied with the known per-packet overhead for the selected
    transport and the maxprate value to determine the worst case bit-rate
    from the transport to more accurately capture the required usage.
    Summing TIAS values independently across "m=" lines and multiplying
    the computed sum with maxprate and the per-packet overhead would
    inflate the value significantly.  Instead performing multiplication
    and adding the individual values is a more appropriate usage.	

First, there is no difference between multiplying on m= block basis and 
then summing versus first making the additions of the maxprate and then 
multiplying given that the overhead value is the same for all m= blocks.

Only if the overhead value is different do one need to multiply on m= 
block basis first and then adding the values together. However, based on 
the definition for overhead and how bundle groups work, I don't really 
expect different overhead values.

It might be best to recommend that one does perform the multiplication 
first and then addition between m= blocks to be certain. But, I think 
the motivation should be more in case there should arise future cases 
where overhead may have different values within a bundle group.

Comments?

cheers

Magnus Westerlund

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From: Suhas Nandakumar <[email-masked]>
Date: Tue, 22 Sep 2015 14:25:37 -0700

Hello Magnus

  Many thanks for the analysis and sorry for the delayed response.
  I agree with you on the overhead across bundle group being same and go
with multiply first and sum next.

Given that, I see the current assignment is SPECIAL and the note clarifies
the point.

So the question is should we keep the current assignment and note same or
are you recommending a change in them ?

Cheers
Suhas

On Fri, Sep 11, 2015 at 7:28 AM, Magnus Westerlund <
[email-masked]> wrote:

> first and then addition between m= blocks to be certain. But, I think the
> motivation should be more in case there should arise future cases where
> overhead may have different values within a bundle group.
>
> Comments?
>
> cheers
>
> Magnus Westerlund
>
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