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<div class="moz-cite-prefix">Am 07.03.2013 12:00, schrieb Emmanuel
Lochin:<br>
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Both are complementary for me : you are faster with ARQ over small
RTT and faster with erasure coding over long-delay link.<br>
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So, the decision whether to do ARQ or to use erasure codes depends
on what you want to achieve.<br>
<br>
A typical trade off. <br>
<br>
This is, however, different from congestion control.<br>
<br>
Congestion control has basically two - contradictory - goals: <br>
1. Fully utilize a channel<br>
2. Not over utilize a channel.<br>
<br>
The problem is that we, in general, don't know a channel's capacity.
<br>
<br>
And in my view, the problem with VJCC is, that it doen't scale with<br>
- networks becoming larger (in terms of e.g. RTT) and<br>
- link throughputs becoming larger (actually, we talk about terabit
links)<br>
and that VJCC cannot really cope with RTT and path capacity becoming
non stationary. <br>
<br>
Another problem is, spoken in the analogy of control theory, that
VJCC attemps to control the filling levels in a multi tank system,
while we only observe whether or not "liquid is dropped somewhere"
and the only possible influence is to control a single tap.<br>
<br>
And as we notice that this will not work, we invent sophisticated
algorithms for controlling the tap or - which is quite modern for
quite some time now - additional taps where liquid my drop. So,
liquid drops not because of an overloaded system but because of an
"active dropping management" - this sounds more scientific. <br>
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