Author Topic: Question on Download Speeds?.  (Read 225 times)

saltyseadog

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Question on Download Speeds?.
« on: November 03, 2018, 11:34:22 AM »
I use the latest version of qBittorrent v4.1.3 in conjunction with a nominated forward port in AirVPN on my Windows 10 desktop PC. I use the Vivid 200Mbps broadband package from Virgin Media. Since approximately 6mths ago my download speeds which varied up to 20Mib/s with a well seeded single download have dropped to a total cap of 4.6 - 5.0Mib/s with 2.5Mib/s being average on a single well seeded download. Unsure whether this is being caused by Virgin Media, AirVPN or qBittorrent. The thing is I am still getting decent downloading times and in researching this came across an article on MB/s and Mib/s where one was a tenth of the other and perhaps this is the reason. Overall I am trying to find out whether anyone else has experienced this as perhaps it is just some setting needs adjusted?. Any way any information on this much appreciated.

Switeck

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Re: Question on Download Speeds?.
« Reply #1 on: November 04, 2018, 11:26:14 AM »
qBT's speeds are in KiloBYTES/second.
Roughly 1000 KiloBYTES/second (1024 to be exact) is 1 MegaBYTES/second, sometimes called 1 MiB/sec

There's 8 bits to a byte if doing a simple conversion...but with qBitTorrent this involves also the BitTorrent protocol which has overheads which runs on TCP/IP networking which also has overheads which is likely also running on DOCSIS 3.0 (from Virgin Media ISP in the UK)...which also has overheads. (I forgot the AirVPN overheads -- they're a few % probably as well.)

So that 1 MiB/sec can take anywhere from 10 to 100+ megabits/second raw network traffic to transmit or receive -- usually it takes a bit of BOTH even if only doing DLing or ULing. (Even TCP has ACKnoledgement packets, ACKs for short, just to tell the other end "yes I received the last bit, send more!" uses about 2-5% as much UL as it takes to DL something.)

As you've already seen, that 200 mbit/sec DL max broadband connection can do about 20 MiB/sec. (UL is likely ~1/10th as much, especially since UK is mostly an island nation and outgoing bw is slightly expense.)

What changed over the last 6 months can possibly be determined pretty quickly if you can run a bandwidth monitor on the raw traffic sent to/from AirVPN.

If it's ~20-50 megabits/second DL bandwidth when you're downloading at 2.5-5.0 MiB/sec then you can assume something is crippling the speeds. (That is you have "enough" active busy torrents to max your DL speed. Make sure you're not maxing your UL at the same time or bufferbloat can happen, which can create a phantom lower DL max.)
Try a speed test through AirVPN with nothing else going on -- if it can max out your 200 mbit/sec connection, then it may not be the problem unless it or its upstream provider is throttling or mangling your BitTorrent traffic.
Your ISP (Virgin Media) may be to blame, based on a promise they made ~10 years ago:  https://forums.theregister.co.uk/forum/containing/387950

A "worse" result might be you see close to 200 megabits/second DL bandwidth when you're downloading at 2.5-5.0 MiB/sec -- the "overheads" I mentioned earlier have becomes bigger than the data payload (the parts you care about). It's like using a 5-ton mail truck to deliver a single postcard, rather inefficient!
Now why that can happen is due to extremely aggressive settings and very busy torrent swarms, where 100's of peers+seeds are trying to handshake with your connection every second. That can happen due to aggressive BT clients or even DoS attacks on those torrents. It's also why I don't recommend a half open limit over 10 even for most "fast" connections.

DeathStalker

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Re: Question on Download Speeds?.
« Reply #2 on: November 09, 2018, 10:30:10 PM »
I'm curious about this as well.  I use uT 2.2.1 on PIA, and I have a 1gb up/down line - however, I'm lucky to get anything greater that 20MB/s on a DL, and greater than 3-4MB/s up - and usually <1MB/s up - it's pathetic.  I hate the higher versions of uT.

DeathStalker

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Re: Question on Download Speeds?.
« Reply #3 on: November 10, 2018, 01:51:41 AM »
Just to add - I was able to (pretty much) successfully import all my uT 2.2.1 titles into QBT, HOWEVER, I get ZERO uploads, nothing.  If I shut down QBT and re-launch uT, my uploads are fine (just not very fast), but consistently more.

Switeck

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Re: Question on Download Speeds?.
« Reply #4 on: November 10, 2018, 08:42:04 AM »
DeathStalker, what was the result of your overheads test of PIA?
When it was downloading at 20 MB/sec, was it really using only 170-200 mbit/sec bandwidth?

DeathStalker

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Re: Question on Download Speeds?.
« Reply #5 on: November 10, 2018, 09:39:23 PM »
2.2.1 does not have the option to show any overhead - I only get the total up/down speed (in MB/s or kB/s).  IUp speed in QBT is ~100 KiB.  Seems like kB/s & KiB/s are the same thing.

Switeck

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Re: Question on Download Speeds?.
« Reply #6 on: November 11, 2018, 06:20:43 AM »
uTorrent does indeed have an option to show *ITS* overheads in its graphs. But it shows them in KiloBYTES/second not raw kilobits/second.
You need a bandwidth monitoring program to show you that. Even windows task manager's networking section might do.

qBT also displays its speeds in KiloBYTES/second...but it's still pretty poor at estimating its overheads.

DeathStalker

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Re: Question on Download Speeds?.
« Reply #7 on: November 11, 2018, 06:44:25 AM »
Either way, it doesn't seem that I'm getting any appreciable difference from QBT.

That, combines with the issue of import failures on partial DLs and the issue of queued vs seeding, leads ne to believe that QBT is not yet ready for prime time, nor is it advisable to switch if you have unfinished DLs in uT.

I'm also, overall, just not seeing any significant advantage with QBT over uT 2.2.1 - now BiglyBT has the *potential* to be better, speedwise, but they still have a LOT of issues to work out.

Right now, to me, it seems more like a personal preference, as opposed to a performance situation.