Thread: Why is capping downloads a good thing?

You might ask yourself why capping your download speed is a good thing for both Torrents and yourself, especially your ratio. Isn't it better for the other peers for you to download the whole file as soon as possible and then just seed it?

The short answer is no.

While you are a part of a torrent swarm, actively downloading the files, you are connecting to peers and offering them data, as well as requesting it. As part of this communication, you are also telling the other peers what pieces of the files you are downloading you have available - and those peers also see how fast you are able to send and receive data to them. The Bittorrent protocol is built with what can be called a weighted load metric; meaning, the peers will prefer to send and receive data to those who are offering fast exchange of data. It will not only pick the shortest route to get pieces, it will also choose the fastest. Bittorrent is also built around the concept of sharing - peers will prefer to send data to peers that are offering data back to them.

While you're downloading, your bittorrent client continuously exchanges pieces of the files almost on a "You give me yours, I'll give you mine" basis, which is the optimal method for bittorrent swarms to operate.

Now, you are probably still asking "Yes, but why can't I do this just as well when seeding"?

In short, when you've completed your download and started seeding, you are no longer really part of the 'swarm' anymore - you become a place the swarm goes to when it needs another piece of the file to distribute in between themselves. Instead of all the 40 peers downloading the piece from you, one peer will download it, and then start passing it around amongst themselves. All the 40 members might need that piece of the file, but those peers, who are continuously talking to each others, will know right away that the piece is available amongst the peers, and prefer to download that piece instead of asking a seed for it.

So, how does capping your download speed help with this? Simply put, it ensures that you remain an active peer for a longer period of time, allowing you to be a part of that network of piece exchange rather than being a seeding point - throwing out that one piece to ensure that the peers can exchange it between them.

Now, a lot of people will no doubt look at the title of this thread and go "Huh? Capping my download?! Why would I want to do that?". And yes, it does perhaps go a bit against logic. But let's look at the advantages and disadvantages of capping your download speed:

Advantages:
* Higher share ratio - You are part of the swarm for longer, distributing your pieces more to your peers. This makes your torrent ratio increase.
* Less seed load - You are putting less load on the valuable seeders' bandwidth capacity, which might be put to better use seeding new torrents.
* Faster swarm speed - By capping your download speed, you are actually /increasing/ the speed of the swarm, giving those who need every ounce of speed more resources to pull from.

Disadvantages:
* You'll have to wait a bit longer for the file to complete. Yes. That's all the disadvantages there are to this.


So, what's a good speed to cap your download speed at? Well, that depends on what your goal is. If you want to get your ratio as high as possible, cap your download speed to be the same as your upload speed - or perhaps even less. But be sure that you have enough pieces to send out! Perhaps let 20-30% of the torrent download at full speed first, then cap your downstream to the same as your upstream. That way, you'll be pretty close to a 0.7-0.8 ratio by the time you're done downloading and become a seed.
If you really want to build ratio, cap your download to /less/ than your upload speed.



If you want to maximize the swarm speed, but still get the file fairly fast, cap download to about 200-300% of your upstream speed. So, if your upstream speed is 500Kb/sec, set your download to 1500 or 1000Kb/sec.

Both of the above achieve the same goal of decreasing the load on the seeds.

For more information on the anatomy of bittorrent swarms and how to optimize your performance in a Bittorrent swarm, google about a bit, or read the excellent Azureus wiki.

Great info!

Would partial seeding keep you in the swarm? (ie. setting a couple files to "Do Not Download" but downloading the rest of the torrent)

Originally Posted by Nebulus

Great info!

Would partial seeding keep you in the swarm? (ie. setting a couple files to "Do Not Download" but downloading the rest of the torrent)

It won't keep you in the swarm since the only reason you keep inside it is since you are also actually downloading from the swarm itself instead of only uploading what you already have. =) Following what the guide on top here says, I don't know all about how bittorrent works and how it prefers certain things. ^^

Originally Posted by Nebulus

Great info!

Would partial seeding keep you in the swarm? (ie. setting a couple files to "Do Not Download" but downloading the rest of the torrent)

Well, no..

Interesting read. You wouldn't think that would be the way to maximize the ratio on the torrent.

I'll give it a shot and see what happens.

Thanks for the info!

Originally Posted by DrunkenBum

Interesting read. You wouldn't think that would be the way to maximize the ratio on the torrent.

I'll give it a shot and see what happens.

Thanks for the info!

good luck m8

Hm.. Quite Interesting, I have always downloaded maybe a rar or two as fast as I can and then seeded it..

Have worked so far, But I will try to cap the download when I have a bit of the torrent. Thanks

Originally Posted by Unitard

Hm.. Quite Interesting, I have always downloaded maybe a rar or two as fast as I can and then seeded it..

yh, that works to

Great info , thanks :)