On Friday, January 05, 2007 Adam Fisk wrote:
> Tit-for-tat is basically providing incentive to keep your client
> running.
I would argue that it is actually a way to loosely group the
similar-bandwidth hosts together in the cloud. Not entirely sure why
- maybe this simplifies the selection of peers, allowing you to use
what amounts to a constant constant number of them instead of having
to grab more and more when their cumulative uplink bandwidth happens
to be inadequate.
In any case, if you are downloading, your client is already
running, isn't it? Unless you're talking about "keep the honest
client running", as opposed to the hypothetical cheating leecher
client, which is really made pretty impractical by tit-for-tat.
(Not sure how serious this problem was to beging with, but that
is a long discussion.)
Best wishes -
S.Osokine.
5 Jan 2007.
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of Adam Fisk
Sent: Friday, January 05, 2007 12:47 PM
To: theory and practice of decentralized computer networks
Subject: Re: [p2p-hackers] HTTP design flawed due to lack of
understandingofTCP
Hi Peter- I've come to this view after closer work over the last several
years with the IETF and more intimate experience with protocol design in
implementing various IETF protocols, particularly within the SIP family. My
initial forays into protocol design came from working on many different
protocols on Gnutella, and some of the Gnutella protocols suffer from the
same problems as BitTorrent.
In a nutshell, well-architected protocols are designed to do very specific
things well. This allows each protocol to evolve independently, with each
protocol yielding control to others in the stack at the appropriate levels of
abstraction. In SIP, this approach is readily apparent and strikingly
effective, with SIP exclusively establishing sessions, leaving the Session
Description Protocol (SDP) to describe the session, the MIME specifications
within SDP to describe the type of media the session will handle, and with
STUN and ICE handling thorny NAT traversal issues. Each protocol is
independent of the others, with these discrete building blocks leading to
incredible flexibility as the protocols evolve. It also allows discrete open
source projects to be extremely focused in the protocols they implement.
One key to these principals is to re-use protocols effectively. With
everyone in the world implementing and understanding MIME, SDP can
interoperate much more easily if it also uses MIME. For file transfers, HTTP
is the universal standard for lots of good reasons. BitTorrent uses
effectively a proprietary file transfer protocol, thereby breaking
interoperability with the rest of the Internet. While BitTorrent is "open"
in the sense that anyone can implement it, it's almost worse than being a
closed protocol because it doesn't fit in with any of the very well-designed
other protocols out there. It would never have a chance to interoperate
with, say, SIP or XMPP because it just implements everything as it damn well
pleases.
I say the features of BitTorrent don't come anywhere near justifying this
because the primary reason for breaking HTTP is tit-for-tat support.
Tit-for-tat is basically providing incentive to keep your client running.
That's more or less fine, but that piece should not be coupled to file
transfers. At a protocol design level, that's just insanity. It also comes
at a tremendous cost. Every web server on the planet is now an invalid
source for a file! Excluding the most powerful computers on the Internet
from the distribution system doesn't seem like a sound design decision,
particularly for the poorly conceived tit-for-tat justification described
above.
I actually have lots of other issues with BitTorrent, but the protocol
layering issue might be the biggest.
-Adam
On 1/5/07, Peter K Chan <[EMAIL PROTECTED]> wrote:
Adam,
Your assessment of BitTorrent caught my attention.
How is BitTorrent "breaking interoperability with the rest of the
Internet?" Why is it that the unique features of BT "don't come anywhere near
justifying" it?
Peter
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