I understand the basic concept that torrenting means transferring files to and from host computers (seeds) and recipient computers (peers) in small chunks. What I don’t understand is what would make this process faster between many seed computers as opposed to just one computer transferring it’s complete file to another computer.
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Well lets say there is one seeder and 40 people downloading.
This would mean in order for all 40 people to download with lets say 100mb/s the seeder should have a 40000mb/s upload.
But if you have 100 seeders with 40 downloaders.
Each seeder would only have to have a 40mb/s upload speed.
So in case there is one seeder and one downloader your theory can be correct if the seeder has an upload speed equal or higher than the download speed of the downloader.
Most home internet connections have much higher download speeds compared to their uploads. If you download a file directly from me it doesn’t matter if you’ve got 100Mb/s download capabilities, if I can only upload at 10Mb/s that’s all you’re going to get. However if 10 people can upload the file to you at 10Mb/s each, you can download at your full 100Mb/s speed.
Well, one computer transferring a complete file to another computer is just the way the web and file downloads USED to work.
Problem is:
– the one seed computer (or server back in the day) has to pay the bandwidth costs to upload the whole file – multiplied by however many people download it. Bandwidth used to be a lot more expensive.
– if just one seed has the file, then everyone has to download from that one computer. Depending on upload bandwidth and # of simultaneous upload slots that seed has, maybe only a few downloaders can get the file at the same time. And if one of the downloaders has a really crappy internet connection, everyone else will have to wait a loooong time before their turn to download.
Contrast that with:
– once the 1st downloader has a chunk of a file, now there are TWO seeds with that chunk. So subsequent leechers can get it from two places not just one. And with every new leecher become a seed, with copies of the various chunks, subsequent download of those chunks becomes much faster for new leeches.**
– if I am not the only seeder, someone’s download of the file isn’t going to cost my bandwidth the full hit for the file – the cost of uploading is spread out amongst all the seeds.
** this is what the tracker does – when your torrent client has pieces of the file, it tells the tracker “hey. I’ve got part of this file.”. Then, when another client asks the tracker “who has pieces of this file?”, the tracker points that client to you; that client then asks yours what pieces you have and can it have some?
Each single seeder is limited by their own upload speed. Typically, your internet service provider limits both upload and download speeds with upload speeds being significantly less than download speeds.
So, for example, your download speed potential is 5Gbps, however you have ONE seeder who is limited to 1.5Gbps upload. You therefore, are limited to downloading only 1.5Gbps because that is all the uploader can do.
Now, if there are 5 seeders at 1.5Gbps each, that’s a total of 7.5Gbps uploading potential. So you can then download at your 5Gbps max speed allowed by your ISP restrictions.
Theoretically, bandwidth permitted by the seeder, you can reach the same speeds with just 1 seed as 100 seeders. Seeders may not want to allocate the entirety of their upload bandwidth. It’s also common the seeders upload bandwidth, set by the ISP, may be limited to a speed much lower than your available download bandwidth. In that case, multiple seeders, each contributing small portions of their upload bandwidth, contribute to try to achieve the maximum speeds your download can allow.
I need a book. I know of a system where people have the books in their computers, so you can ask them for a specific page and they’ll send it to you. The system works by your computer asking “hey, I need the page 1”, the other computer says “ok, I’m sending page 1”, then after receiving it your machine would reply “Ok, I received page 1”, and repeat for each page.
Now, the system limits you how many pages can you ask to a specific individual. But, nothing stops you from asking multiple people for different pages at the same time.
I think I would try to explain it to 5 year old me like this. Imagine you want a copy of a book, but must get the pages via physical letter. Every letter fits let’s say 10 pages. Then let’s assume that one person can send one letter per day, because the post guy won’t accept more letters.
For a book with 100 pages, you need 10 letters with 10 pages each, right? So if you only had one person sending you the letters, they would need ten days to send off everything.
If you have two people that each send different portions of the book, the time halves to 5 days. 5 people could do it in two days and ten people in one day.
Now exchange pages with data, letters with packets, person with seed, post guy with upload rate and days with a much shorter timeframe.
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