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

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 <
magnus.westerlund@ericsson.com> wrote:

> 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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