[e2e] A metric to evaluate RTT estimation techniques for layered (multi-rate) multicast protocols

[Arnaud Legout]

Hi,


Osman Ghazali (FTM) wrote:

>Finally, again, 
>Is there any metric for RTT estimation techniques (for layered maulticast) ?
>or 
>Any suggestion of how to evaluate RTT estimation techniques (for layered 
>multicast) ?
>  
>
it is not possible to answer such a question if you don't say what you 
want to do.
In case you want to be TCP-friendly, find your worst receiver and 
measure the RTT with respect to him
as if it is a unicast receiver. If you don't want to slow down too much 
your MC session, define a criteria
to find a representative receiver. Here again, the problem is the same 
as for unicast RTT.
In both cases, the problem is not RTT estimation, but representative 
receiver discovery.

If you want to do something else, how do you use the RTT?
If you have a layered multicast scheme, you probably have a receiver 
driven protocol. In this case does it
make sense to use a RTT estimation, which supposes to send feedback to 
the source.

In case you use OTT, is it relevant in your context (asymmetric links, 
etc.)?

I know that I don't give any hint on how to measure the RTT for layered 
multicast, but I would like
to stress that is is very dependent on what you want to do.

Regards,
Arnaud.

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Arnaud Legout, Ph.D.

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