Per Torrent Connections vs. Total Torrents Tweaking

[flak]

The speed guide sets connections per torrent for xx/768 to 100. Thing is, the trackers I use only occasionally reach that number of seeders + peers combined per torrent.

That being the case, would I get an acceptable balance if, for example, I halved the connections per torrent to 50 and doubled the maximum number of active torrents from the recommended 5 to 10? My thinking behind this is two-fold: 1) to allow seeding of existing torrents for an extended period of time without having to stop and restart them when I want to download some new torrents in the interim; and 2) to maximise the potential of seeders on the tracker I use who always provide lightning fast upload speeds (2Mbit being the minimum).

Would that help?

And as an aside, if I want to cap my upload speed when downloading a torrent, but want to increase it when all my active torrents are only seeding, am I right to say that I would do that in Preferences => Connection?

e.g. Global maximum upload rate = 70kB/s

Alternate upload rate when not downloading = 80kB/s (box checked)

Hope that makes sense.

[Ultima]

Number of connections isn't the only thing you should be looking at when deciding your settings. The problem with starting too many torrents at once is that you spread your upload rate way too thin. Realize that under xx/768k, there are 5 upload slots per torrent. If you have 10 torrents started, you can potentially have up to 50 upload slots open (give or take a few). Assuming you are uploading at the maximum of 72KiB/s set by xx/768k, do realize that you're spreading your upload over 50 connections, meaning each peer will be downloading from you at 72/50 = 1.44KiB/s -- it's very low.

[flak]

Ultima

Thanks for your quick response.

I understand -- more or less -- what you're saying, but the likelihood is that some of the active torrents are actually only idling (no leechers), and consequently don't require the use of an upload slot; most of the time, the real number of upload slots being used is well below the theoretical 50 (using the example).

That said, I do notice that my upload speed loses around 20-30% of its global maximum when I'm downloading, and I had always chalked that down to having too many connections per torrent.

What I want to do is give myself the best possible chance of connecting to the fastest peers and return the favour by giving them the bulk of my available upload speed. I appreciate that P2P protocol operates in such a fashion, anyway, but I'm hoping for some suggestions that would allow me to maximise my download/upload potential as it specifically relates to a fast tracker. Put another way, how do I go about targeting the most desirable peers/seeders in the swarm when I know that, on average, the supply of bandwidth exceeds demand? My thinking is that artificially lowering the ceiling for number of connections per torrent, in addition to limiting upload slots per torrent to, say, 3 would help my cause.

What do you (or anyone else) think?

[Ultima]

Mm... I suppose lowering the upload slots to 3 per torrent would indeed improve that situation. Looks like there probably won't be too much of a problem doing it your way...

My agreeing with you could just be a case of me not thinking critically enough at the moment, so I suggest you wait a bit for other opinions before taking mine

[funchords]

My advice would be to stick to the recommended settings, but then use the "Up/Down" arrows and the "Force Start" function to make exceptions when you recognize the special situations that you are mentioning (e.g. the "all seeder" swarm). You can also set individual slot allocations per torrent in the Properties of each.

Your tastes may change, you may discover new tracker systems or a new set of downloads that don't follow your current situation and assumptions. Staying with the recommended settings means that your client's "autopilot" will follow some conservative rules, but you're still able to "take the stick" when needed.

Tests have shown that the optimum number of connections in a young, healthy, popular swarm is some number that usually falls between 50 and 110. Before that point, adding more peers brings with it a substantial increase in download speeds. After that point, continuing to add new peers brings diminishing increases. The point itself is the "knee-of-the-curve."

But here's a major constraint -- Many light-duty residential routers have a NAT table capable of storing only 150-300 simultaneous connections. The settings are such that you can balance these needs -- setting a hard overall limit, but being sure to get well connected into any swarm that you join.

A connection setting of 75 connections per torrent, with a total connection limit of 200, and a limit of 5 torrents may not sound mathematically correct. However, it is a reasonable configuration for someone with bandwidth like yours and a normal home-use router.

[flak]

Ultima, I encourage your best critical thinking side to come out and play

funchords, interesting stuff. In practice, however, I'd prefer it if your recommendations could be flipped so that it became a guide to follow on a 'need basis,' instead. I can't help but feel that 75 connections per torrent is still excessive for my normal needs and, therefore, isn't a productive allocation of resources. Also, my present setup uses direct connection and no router, so my bandwidth isn't limited in that regard.

I suppose what I need is a better understanding of the mechanics of utorrent. (or any other client, for that matter.) For example, if my connections per torrent is x and I have set the number of upload slots per torrent to y (being 1/10 of x), how does the client determine who among those I'm connected to gets my upload bandwidth? Assuming similar speeds, is it random, does it go for a peer that follows a path of least resistance, or something else?

Let's also say that, for the purposes of this argument, I max out global connections despite there being a greater combined total in the swarms of my active torrents. In such circumstances, would the program seek out faster speed seeders/peers? And does it follow that the lower my connections per torrent limit the more aggressive my client becomes in targeting the best users? My theory is, the bigger the swarm the less discerning the client becomes, first, with who it connects to, and, second, who to then download from/upload to. So, quantity over quality, then, when what you want is the opposite.

It's like if I was looking to buy new hi-fi gear and was determined to burn a hole in my pocket, although I wouldn't exclude the cheap stuff, my focus would be on high-end equipment. Another analogy would be a kid in a candy store. Give him free reign on a big budget, chances are he'll want a bit of everything as opposed to a lot of just one thing, and not be overly concerned with how good it tastes. Tell him that he can only choose a few kinds, however, and the probability is that, if he's smart enough, he'll sample the merchandise first to make darn sure that, with a limited choice, he's getting something he really likes.

Bottom line: What I want is to try and get the highest speeds from as few seeders/peers as possible -- 1 seeder/peer who'll give me 100kB/s instead of 10 seeders/peers giving me 10kB/s each. Wouldn't that make sense on a tracker with fast speeds but a comparatively small swarm?

[Switeck]

There's also advanced settings in µTorrent:

1.to allow additional upload slots if upload speed is consistantly below 90% of your set max.

2.to start additional torrents if currently uploading OR downloading torrents aren't going over 1 KiloBYTE/sec each.

So there's no need to set your max active torrents OR upload slots very high.

Do note that in repeated tests I've done that setting upload slots below 3 for downloading torrents or 2 for uploading torrent SEVERELY impacts your download (for downloading) and upload speeds (for seeding) if you're on marginal torrents with lots of crippled peers on hostile ISPs. ...which many are.

1 upload slot is always reserved as a "roaming" optimistic unchoke slot and never stays uploading to a particular peer for more than 15-30 seconds. If it connects to a really bad peer, then upload speeds can be "dead" for 15-30 seconds before it changes to a new peer.

For a single seeder to give you 100 KiloBYTES/sec download speed, it has to have 100 KiloBYTES/sec upload speed devoted to JUST YOU. However even if it has default settings of 4 upload slots and only seeding the 1 torrent, then it is probably uploading a roughly equal amount to 3 other peers...or in other words 300 KiloBYTES/sec of upload speed to 3 others for 400 upload speed total. That takes at LEAST 3400 kilobits/sec upload bandwidth and is only barely possible for something like Verizon's recent FIOS 20/5 lines...which are definitely the extreme exception rather than the norm for home broadband connections. And that is if they were only running 1 torret with 4 total upload slots. If they're running 10 torrents with 10 upload slots each, then even a 100 megabits/sec upload bandwidth line probably couldn't sustain 100 KiloBYTES/sec per person. ...and those are almost nonexistent except in places like South Korea and Japan.

It is actually exceptional to get more than 10 KiloBYTES/sec download speed from a single seed or peer...as even with 1 torrent with 4 upload slots, this implies they have 40 KiloBYTES/sec total upload speed. My total upload speed is only 42 KiloBYTES/sec by comparison, and I typically have 2-3 torrents going at once with 2-5 upload slots each. (I typically reduce upload slots when I increase active torrents.)