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RE: [ns] goodput calculation
"pawan.g" <[email protected]> wrote:
$ is this definition of goodput correct.
$
$ goodput = (max no of pkts recvd by the rx in sequence)
$ / (total number of pkts sent by the sender
$ including retransmissions)
(assuming constant packet/segment length)
That's actually a kind of efficiency measure resulting from
(goodput/throughput). The intervals cancel out.
Michael Welzl <[email protected]> replied:
> I think the reason for all the issues Lloyd brought up is that
> there is no such thing as a "correct definition of goodput".
> But I would say that goodput should always be related to a
> bandwidth measurement - bytes / interval. That is suggested by
> the similarities betweeen the names "throughput" and "goodput".
Things like slowstart play havoc with division over a measurement
interval.
[..]
> This definition should conform with how Lloyd defines goodput as
> he is interested in how much is actually handed to the application.
> Which is a sensible way to define goodput.
>
> Still, it is not always defined like that - that depends on the
> context. For instance, papers which do not consider retransmissions
> may define goodput as "throughput seen by the receiver" as opposed
> to "throughput used by the sender".
no retransmissions == no drops signalled back to the receiver. what
papers are these?
> Come to think of it, the only actual difference is at which network
> layer your "receiver" is located.
And where in the network. You've forgotten about drops en route
again...
L.
<[email protected]>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>