[PLUG] Torrent download speeds - was: Metrofi wins Rogue of the Week

John Jason Jordan johnxj at comcast.net
Sun Jan 13 07:21:22 UTC 2008


On Sat, 12 Jan 2008 20:40:56 -0800
"drew wymore" <drew.wymore at gmail.com> dijo:

> <snipped>

> > > I just checked, and you are correct. I use Ktorrent, which reports
> > > download speeds in KB/s, not Kb/s.
> > >
> > > Having said that, often torrents download at only 5-10 KB/s. At the
> > > moment I am downloading Gentoo amd64 and it is averaging about 500
> > > KB/s. But it depends on lots of other factors. Even assuming that 500
> > > KB/s is the same as 5000 Kb/s, the tests I used (suggested by Joe and
> > > Mark previously) ranged from 7800 to 23,500 Kb/s, so I am still limited
> > > by something other than the maximum Comcast is giving me. In fact, it
> > > always seems to be something other than the Comcast limit.
> >
> > Torrent is as slow as the slowest machine out there acting as a server
> > to you.  There may be some folk with modems, and most broadband services
> > (cable and DSL) have much slower upload (downloading to you) then
> > download (uploading to you).  Adding in handshaking (to those slow
> > sites) and it gets even worse - you are waiting for the snail-slow
> > handshake packets to leave their machines.
> >
> > So you may have very fast download, from a real server on a fast link,
> > but unless you are communicating only with high-speed-bidirectional
> > peers you will see some slow behavior from torrent.  You are on Comcast,
> > with 6Mbit download and 384Kbit upload maximums.  On a "fair" torrent,
> > you will be uploading as much as you are downloading (slowing down both
> > directions), and you will be losing a lot of speed to handshaking and
> > and overhead.  So, you should expect to see a maximum of 20KByte/sec
> > behavior from torrent;  any more, and you are taking more than you give.

> You nailed it very well Keith. Depending on how many peers you can connect
> to and which machines have the pieces of the torrent you currently need.
> I've had really good speeds and then see them drop to near nothing only to
> pick back up minutes later after I had received whatever piece I needed that
> happened to be sent to me via a slower peer. Comcast's traffic shaping (if
> they are still doing it, and I have some non-scientific data from my torrent
> use that suggests they are) still really sucks, but as I think has been
> mentioned before, it is their network and they are allowed to do whatever
> they please. I do find it odd that it doesn't appear that they are shaping
> Gnutella traffic.

The other day while downloading the Gentoo DVD ISO it started out at
750-850 KB/s. By the time it ended the speed was down to 350-450 KB/s,
and Ktorrent told me the final average was about 500 KB/s. Throughout
the download time I would look at Ktorrent from time to time and the
same seeders were present all the time - that is, all seeders had 100%,
all but three were choked, and there were no leechers besides me. The
same three non-choked were always seeding me. The total speed might
drop, but the percentage of the total that each seeder gave me was
roughly constant. For example, if the total amount was 500 KB/s, one
seeder in Germany was giving me roughly 325 KB/s, one in Brazil was
giving me about 150 KB/s, and one in the US was giving me around 25
KB/s. When the total was 700 KB/s the same seeders gave me the same
ratios of the total.

I recall downloading Gutsy on the day it was released. There were
hundreds of seeders and hundreds of leechers. Yet I never saw a speed
in excess of 100 KB/s, in spite of the fact that there were dozens of
non-choked seeders with 100%, many of whom were sending me nothing. 

The problem is that there is no way for me to tell what is actually
happening. From the above it makes me want to think that Comcast senses
when I am using a torrent and "shapes" my download so I am slowly
throttled back during the download. But am I being paranoid to think
that? I don't know and, absent information from a snitch inside
Comcast, I will probably never know. Torrents work in very mysterious
ways. 

I can add that during the Gentoo ISO download I also installed a couple
dozen upgrades for my desktop computer with Download Manager, some of
which were multiple MB. Those downloaded at 500-600 KB/s and I watched
the Gentoo download speed as the upgrades downloaded. The Gentoo
download was unaffected. In other words, I had additional download
capacity throughout the Gentoo download. If the three that were seeding
me were not choked, why did they not send at a faster rate? Because
Comcast was "shaping" my download? Because Ktorrent reports them as not
choked when they really are? Very mysterious things, these torrents.



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