Note that this will only give you a lower bound; the true losses that were
addressed by the sender (ie. RTO retransmissions that got lost again) can by
principle not be discovered by a receiver side trace, only a (reliable)
sender side trace will allow that.
To the second point: Only for simple Reno/NewReno there exists a closed
formular for estimating throughput based on random, non-markow distributed
losses; and more modern congestion control / loss recovery scheme will
permit (more or less slightly) higher thoughput, thus the formulas (ie. RFC
3448 states the one for Reno) will only serve as a (good) lower bound
estimate.
Again, increasing throughput at the cost of goodput is a bad proposition, if
you get charged by traffic volume (because what you really want is data
delivered to the receiver, not dumped into the network for no good reason).
Regards,
Richard
----- Original Message -----
From: "Fred Baker" <[email protected]>
To: "richard" <[email protected]>
Cc: <[email protected]>
Sent: Friday, May 06, 2011 11:56 PM
Subject: Re: [Bloat] Goodput fraction w/ AQM vs bufferbloat
On May 6, 2011, at 8:14 AM, richard wrote:
If every packet takes two attempts then the ratio will be 1/2 - 1 unit
of googput for two units of throughput (at least up to the choke-point).
This is worst-case, so the ratio is likely to be something better than
that 3/4, 5/6, 99/100 ???
I have a suggestion. turn on tcpdump on your laptop. Download a web page
with lots of imagines, such as a google images web page, and then download
a humongous file. Scan through the output file for SACK messages; that
will give you the places where the receiver (you) saw losses and tried to
recover from them.
Putting a number to this will also help those of us trying to get ISPs
to understand that their Usage Based Bilking (UBB) won't address the
real problem which is hidden in this ratio. The fact is, the choke point
for much of this is the home router/firewall - and so that 1/2 ratio
tells me the consumer is getting hosed for a technical problem.
I think you need to do some research there. A TCP session with 1% loss
(your ratio being 1/100) has difficulty maintaining throughput; usual TCP
loss rates are on the order of tenths to hundredths of a percent.
_______________________________________________
Bloat mailing list
[email protected]
https://lists.bufferbloat.net/listinfo/bloat
_______________________________________________
Bloat mailing list
[email protected]
https://lists.bufferbloat.net/listinfo/bloat
