[p2p-hackers] p2p in some place or other

[David Barrett]

Serguei Osokine wrote:
> On Sunday, December 11, 2005 Travis Kalanick wrote:
> 
>>So far, in my opinion, proactive caching on open p2p networks would
>>provide little temporal benefit in availability and performance, 
>>given the inherent costs of such a scheme, and given the availability
>>of high-performance, high-reliability p2p architectures.
> 
> 	...and I was on the other side of this debate.

... and I'm somewhere in between.

I suspect proactive caching is useful for some configurations of files, 
uploaders, and would-be-downloaders, but I'm not sure if that 
configuration exists in the real world to such a degree that it's worth 
worrying about.  Furthermore, I suspect the "real world" in all its 
glory is far too complicated to get agreement upon quickly, so I think 
we should first start with simplified worlds and then work up to the 
real one.

For starters, assume "the network" consists of:
1) A single "uploader" with exactly one file
2) A "downloader" that wants the file (but doesn't have it)
3) An "innocent bystander" that neither has nor wants the file

(Further assume that there will never be any more files, more nodes, and 
the innocent bystander will never want the file.  Also, assume all three 
nodes have identical, equal upload/download speeds, unlimited storage, 
and have been and will be online for eternity.)

Thus the uploader can either choose to:
a) Send the file only to the downloader
b) Only to the innocent bystander
c) To both

I'd define "proactive caching" as options (b) and (c).  And in this 
specific configuration, I don't see it as useful.  I'll define "success" as:
- Transfers the maximum number of files to those who want them
- In the shortest possible time

(Note, I'm explicitly not valuing conservation of bandwidth or storage 
in order to simplify the case for proactive caching.)

Thus for this absolute most basic network, I'd say option (a) is clearly 
the right choice.

Can we agree on that much?

If so, what is the *smallest* way this network must change in order for 
proactive caching to begin offering value?

-david