Caching Torrent files in DNS

bodin writes "This is a proof of concept version of BitTorrent where the torrent files are transported over DNS. This will of course bog down BIND servers all over the planet. Everyone should be thankful that the files are not sent over DNS."

Comments

Re:Idiot

[hattmoward]

He's just talking about the .torrent file, which points to a torrent tracker, not the torrent data itself; and DNS works over TCP also.

-1, Wrong

[Wesley Felter]

The tracker does not allocate bandwidth, it just introduces peers to each other.

Re:Not THAT small.

[Zocalo]

Actually, DNS is designed to handle considerably more than just the few bytes of data that would typically be required for an A or PTR record. One reason for DNS supporting TCP was to enable queries of more than 64kB, which are quite often seen on zone transfers, and should be able to cope with the majority of .torrent files.

Plus, I don't see how this is going to put the huge strain on the DNS infrastructure that is implied, apart from the server hosting the torrent's TXT record anyway. Assuming no cached DNS information, I need to perform exactly the same number of DNS queries to resolve foo.domain.com to get a TXT record as I do get pull a tracker file from it. Judging by some of the posts here already some seem to think that the root DNS servers are going to have to handle terabytes of movies files or something, and that just isn't that case.

Re:Not THAT small.

[CowboyMeal]

Not only that, but DNS was designed to handle a lot of tiny requests, and a few huge requests. For the many many tiny requests, it uses UDP, and doesnt have to go through the overhead of a full-blown TCP connection. This is what makes it so scalable. If it has to send back more than 512 bytes (for a zone transfer or torrent file), it sets up a TCP connection, but in the case of a zone transfer, it doesnt have to do this very often.

For a typical name query, only two UDP segments are involved, one for the request and one for the response. If you were to request a torrent file, you would need the first three TCP handshaking segments, one to send the request, and then 1 or 2( depending on the machine setup) to send back the torrent file.

Normal DNS query: 2 segments
Torrent file DNS query: 5 or 6 segments

So that takes 2.5-3 times more processing time per request on the DNS server, and that doesnt even take into account the TCP session state.