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Bittorrent Oddity

 
 
s.t.e.v.e.
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      02-18-2006
I've noticed that when I set my bit torrent client to upload at 18kbps, it
will then - usually - have a download rate of about 13kbps.....and I
generously end up downloading one iteration and uploading 1.5 or two or
even more.

But if I lock the upload rate down to about 10kbps, the upload rate rapidly
climbs to 30kbps, 40kbps or more.....and is sustained there.

That seems odd to me......or is it? Maybe bit torrent is feeding rapidly to
people to who have little capacity to share (10kbps...)......and making
maximum use of people in a (relatively) better position to share (18kbps)
with more peers?????




 
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s.t.e.v.e.
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      02-18-2006
s.t.e.v.e. wrote:

> But if I lock the upload rate down to about 10kbps, the upload rate
> rapidly climbs to 30kbps, 40kbps or more.....and is sustained there.


Oops...I meant the download rate climbs.....
 
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~misfit~
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      02-18-2006
s.t.e.v.e. wrote:
> s.t.e.v.e. wrote:
>
>> But if I lock the upload rate down to about 10kbps, the upload rate
>> rapidly climbs to 30kbps, 40kbps or more.....and is sustained there.

>
> Oops...I meant the download rate climbs.....


It's a sad fact of life that here in NZ with our non-broadband upload speeds
the upload on bittorrents have to be throttled right back to get good upload
speeds. In fact, I find that anything over 5kB/s up and the down really
suffers. Of course, that means I have to leave it running most of the day
just uploading to try to get a reasonable ratio. I use Azureus and there's
an option to have no set upload speed (ie unlimited) when not downloading.
It's good for when your download's finished.

Bittorrent downloads can have a lot of 'overhead'. Azureus tells you how
much of your data each way is 'protocol'. For my current session (Actrix,
rate-limited to 64kbps each way) the download is 41.72MB, 18.66MB, or 41.7%
of which is 'protocol'.

The protocol goes both ways and if you're uploading at anything near your
actual speed there isn't enough bandwidth to establish downloads and send
the data back to the guy you're downloading off.

So... Yeah... Until we get a higher upload speed, to optimise your download,
5kB/s is the optimum upload speed. As I said, you can always upload later /
earlier to keep a reasonable ratio. However, try as I might, I have trouble
keeping my ratio above .5

Cheers,
--
~misfit~


 
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Mark C
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      02-18-2006
"s.t.e.v.e." <(E-Mail Removed)> wrote in
news:(E-Mail Removed):

> I've noticed that when I set my bit torrent client to upload at
> 18kbps, it will then - usually - have a download rate of about
> 13kbps.....and I generously end up downloading one iteration and
> uploading 1.5 or two or even more.


If you have Orcon Bitstream, the max upload of 128kbps is =
~16kByte/sec. If you set your bit torrent upload to 18kByte/s, then
the line speed is the limit and you are saturating your upload.

You need to leave enough upload bandwidth so that ACKs
(acknowledgments) for the data you are downloading can be sent. If
your upload is saturated with bittorrent, the ACKs get delayed and
your download stalls.

> But if I lock the upload rate down to about 10kbps, the upload
> rate rapidly climbs to 30kbps, 40kbps or more.....and is
> sustained there.


This is because 10kByte/s leaves ~6kByte/s headroom for the ACKs.
(10+6 = 16).

You should also make sure your TCP RWIN is set appropriately:
http://www.dslreports.com/faq/tweaks
http://www.dslreports.com/tweaks
(Select "Jump to topic" and try Tweaktester and RWIN.)

Mark
 
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s.t.e.v.e.
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      02-18-2006
Mark C wrote:

>
> You need to leave enough upload bandwidth so that ACKs
> (acknowledgments) for the data you are downloading can be sent.**If
> your upload is saturated with bittorrent, the ACKs get delayed and
> your download stalls.


Thanks.

That makes sense in pure network terms alone....and certainly accounts for
what I have been seeing.





 
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s.t.e.v.e.
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      02-18-2006
~misfit~ wrote:

> So... Yeah... Until we get a higher upload speed, to optimise your
> download, 5kB/s is the optimum upload speed. As I said, you can always
> upload later / earlier to keep a reasonable ratio. However, try as I
> might, I have trouble keeping my ratio above .5


Thanks....

I usually set a completed download to "dial/isdn" speed (5k upload)....and
let it run for a couple of days......and often until it has a ratio of 2:1.

Especially if it is early in the lifecycle of the particular torrent and
there are many leechers / few seeds.





 
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Gordon
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      02-19-2006
On Sat, 18 Feb 2006 23:19:04 +1300, s.t.e.v.e. wrote:

> ~misfit~ wrote:
>
>> So... Yeah... Until we get a higher upload speed, to optimise your
>> download, 5kB/s is the optimum upload speed. As I said, you can always
>> upload later / earlier to keep a reasonable ratio. However, try as I
>> might, I have trouble keeping my ratio above .5

>
> Thanks....
>
> I usually set a completed download to "dial/isdn" speed (5k upload)....and
> let it run for a couple of days......and often until it has a ratio of 2:1.
>
> Especially if it is early in the lifecycle of the particular torrent and
> there are many leechers / few seeds.


All a seeder has is all the pices of the file. They might be uploading at
a very low rate. Given enough "leechers", a term which is somewhat
incorret if people are giving as much as they give, all the parts of the
file will be avaliable.

 
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Gordon
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      02-19-2006
On Sat, 18 Feb 2006 21:48:42 +1300, ~misfit~ wrote:

> Bittorrent downloads can have a lot of 'overhead'. Azureus tells you how
> much of your data each way is 'protocol'. For my current session (Actrix,
> rate-limited to 64kbps each way) the download is 41.72MB, 18.66MB, or 41.7%
> of which is 'protocol'.


Part of which can be/is corrupted slices. 41% seems somewhat high.

 
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A Nice Cup of Tea
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      02-19-2006
On Sun, 19 Feb 2006 16:53:19 +1300, Gordon wrote:

> On Sat, 18 Feb 2006 21:48:42 +1300, ~misfit~ wrote:
>
>> Bittorrent downloads can have a lot of 'overhead'. Azureus tells you how
>> much of your data each way is 'protocol'. For my current session
>> (Actrix, rate-limited to 64kbps each way) the download is 41.72MB,
>> 18.66MB, or 41.7% of which is 'protocol'.

>
> Part of which can be/is corrupted slices. 41% seems somewhat high.


41% can be possible if most of the seeds and leechers are limiting their
upload speed, causing the protocol to be a higher percentage of the data
traffic than normal. I mean, if there are lots of peers with comparitively
few seeds, and with most of them dialup, and with a large percentage of
the peers with a low percentage of the torrent, then the seeds will have
to be spreading the data around quite widely and at dialup speed. That
means each peer won't be getting much data in one hit until the relative
completion rates of the peers increase sufficiently to enable more data
being shared.

I've seen torrents ebb and flow in their available speed to the extent
that I've stopped a torrent, waiting for a more opportune moment to
resume it.

IOW, nothing to worry about, but for bandwith efficiencies sake, maybe
stop that torrent for a while until it's a little faster.


A Nice Cup of Tea

--
A: because it messes up threading
Q: why should I not reply by top-posting?
A: No.
Q: Should I include quotations after my reply?

 
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~misfit~
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      02-19-2006
Gordon wrote:
> On Sat, 18 Feb 2006 21:48:42 +1300, ~misfit~ wrote:
>
>> Bittorrent downloads can have a lot of 'overhead'. Azureus tells you
>> how much of your data each way is 'protocol'. For my current session
>> (Actrix, rate-limited to 64kbps each way) the download is 41.72MB,
>> 18.66MB, or 41.7% of which is 'protocol'.

>
> Part of which can be/is corrupted slices. 41% seems somewhat high.


Yeah, that's 'cause I was rate-limited back to 64kbps I think. I notice that
there's always a high percentage of 'protocol' when the download is very
slow (and I'm uploading as well). When I'm on a hot one the 'protocol'
percentage is very low.
--
~misfit~


 
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