[BitTorrent] Re: Request for protocol extension: get_info/info messages

iain_wade iwade at optusnet.com.au
Thu Jan 13 19:12:26 EST 2005

> > > Problem is this pollutes things for folks without a cache in
> > > from of them. Why is this needed? If you can proxy the tracker
> > > connection, why is better than modifying the response?
> >
> > I don't consider one extra DNS lookup per program start
> > "pollution".
> One lookup for an invalid domain. Slowing most systems. This also
> strongly advertises your use of BitTorrent to the ISP, who
> shouldn't be informed for privacy reasons (they can analyze the
> traffic to find BT, but your suggestion provides a clear indicator).

Using BitTorrent is not a crime.

Using p2p is not a crime.

Copyright infringement is a crime and looking up btcache.p2p does not
notify anyone as to whether you are doing so or not.

This could be used by an ISP to determine if an individual is using a
BitTorrent client, but they would still need to snoop all your traffic
to see what you are downloading.

This could be used by an ISP to determine what percentage of their
users are using BitTorrent clients, but in aggregate form this
information does not breach your privacy.

> Your million customers represent less than 1% of the Internet.
> Making a cache easy to utilize is acceptable, making intrusive
> changes IMO is not.

I agree.

These are the smallest number of changes possible IMO.

As I said, I would have liked to cache the result of the query but the
official client in particular does not have a config saving facility
currently and I didn't feel the need to add one.

Other client will most likely cache the results for a number of days,
limiting the impact of this change even further.

> Thing is there will be plenty who either explicitly do not wish to
> use it, or don't have one handy. For them it is a disadvantage.

I think your are mis-judging the impact of a single dns lookup.

Every time you type an address into your web-browser your machine
would probably perform at least 4 dns lookups.

an "AAAA" lookup for bittorrent.com.my.search.domain.
an "AAAA" lookup for bittorrent.com.
an "A" lookup for bittorrent.com.my.search.domain.
an "A" lookup for bittorrent.com.

You would perform more if you have a couple of search suffixes, or if
there are inline images.

In contrast, this change performs a single extra "A" record lookup at

> And a non-MitM cache is likely to scale? Seems like they'll both
> run into a wall at about the same time.

The difference is that when a MitM cache hits the wall performance
goes to shit for all the users passing through that system.

The non-MitM cache only augments client participation, it doesn't
control it.

> > I'm not interested in deniability, I want to save bandwidth. I
> > don't save logs, so associating a blob of data on our disk with
> > a user is not possible.
> Good goal. Admirable position. My concern is that less scrupulous
> folks may choose to log, or could be forced to log via court order.
> I'd like it to be that keeping logs isn't useful because they
> cannot be made to yield any information.

Again I disagree. ISP's are probably less likely to run tcpdump on
their nameservers looking to see which users are trying to resolve
btcache.p2p than they are to perform a court-ordered legal intercept
on all of a specific user's traffic.

Trust me, we've gotten really used to handling legal intercepts since

> > Got I hate this YahooGroups interface :-/
> Join the club, though as a mailing list it does mostly work.

I'm getting significant lag here :(

And it didn't accept my last two posts when sent from gmail. maybe the
from address didn't match my list subscription or something :(


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