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Mayutan,<br><br>
At 15:37 21/03/2010, Mayutan A. wrote:<br>
<blockquote type=cite class=cite cite="">Hi Bob,<br><br>
Thanks once again for your feedback. See inline. <br><br>
On Sun, Mar 21, 2010 at 1:03 AM, Bob Briscoe
<<a href="mailto:rbriscoe@jungle.bt.co.uk">rbriscoe@jungle.bt.co.uk</a>
> wrote:<br>
<dl>
<dd>Mayutan, Xiaoming, KK,<br><br>
<dd>Mail #2 of 2: Thoughts on the decomposition itself<br><br>
<dd>Bandwidth-estimation module<br>
<dd>---------------------------<br>
<dd>I propose it's better to think of this as a
Window-overshoot-mitigation module.<br><br>
<dd>i) Bandwidth is the wrong concept. A cc is looking for how much data
it can risk setting off in flight when it's got insufficient information
to determine a precise answer. That's a window concept [unit: byte], not
a bandwidth concept [unit: b/s]. Take QS. The router thinks in terms of
spare b/s. But the transport has to multiply that by RTT to get the
initial window it should use.<br><br>
</dl><br>
Currently, what I have in mind is the estimation of actual bandwidth to
assist the flow-control module and leave it to the flow-control module to
convert this to a relevant window size. In theory, this module could
indicate window size too. Thanks for the alternate name suggestion.
</blockquote><br>
I'm not concerned about just the name. The semantics of window is what I
think you need here, not bandwidth. This is important to get
right.<br><br>
[A similar example: Stas Shalunov pointed out to me once (I think
repeating someone else) that if MTU had been defined in units of time,
not bytes, packets would have grown naturally as link technology
increased and data networking would have evolved very differently.
Effectively the MTU is the liaison concept between IETF and IEEE.
Similarly, the interface to your top module is important to get in the
right units.]<br><br>
<br>
<blockquote type=cite class=cite cite="">
<dl>
<dd>ii) It's not so much about estimating the right window. It's more
about ensuring the window is not too wrong, while trying to otherwise be
as greedy as possible.<br><br>
</dl><br>
By estimation, I meant the above. Thanks for phrasing it well. I should
probably use a different word here or the name suggested by you.
</blockquote><br>
Cheers<br><br>
<br><br>
Bob<br><br>
<x-sigsep><p></x-sigsep>
________________________________________________________________<br>
Bob
Briscoe,
BT Innovate & Design</body>
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