Re: queueing and priorizing strategies

On Oct 8 2007, Arne Babenhauserheide wrote:
> Would it be correct if I stated your idea like the following: "When asked 
> to help by many people, I first help those from whom I expect to get back 
> the most"?

Hi Arne,

That's it exactly.

> Do you include things like "has content which interests me" (aka 'I 
> already downloaded from him/her) into the equation?

Yes, the calculation considers total bytes uploaded to and downloaded from 
the peer during the session (or longer, if long-term peer identifiers are 
available). That could mean parts of the same file (download mesh) or 
different files transferred at different times.

> To include this in Gnutella: Could the leafs publish their receipts ("I 
> uploaded to that one" and "I downloaded from that one") to the Ultrapeer 
> and peruse the existing infrastructure that way? The UP could collect 
> them and push them back to the leafs, so a multi-step utility can be 
> calculated for neighbor leafs.

Interesting idea. You'd have to be careful about collusion (you and I both 
claim to have downloaded 100 GB from each other in order to get faster 
downloads from everyone else), but the phrase "multi-step utility" sounds 
like you might be considering something like max flow, which can be used to 
prevent collusion:

http://www.sigcomm.org/sigcomm2005/paper-CheFri.pdf

> Does your scheme work, if people in the utility chain can drop out (and 
> do so very frequently)?

It depends on a few factors. First, how long do sessions last (especially 
the sessions of people who share a lot of files, which I suspect are likely 
to be longer than average)? Second, do peers have long-term identifiers 
that persist across sessions (eg TLS certificates)? Third, how long is the 
typical delay between uploading to a peer and downloading from the same 
peer, or vice versa? (In the download mesh I guess it will typically be on 
the order of a few seconds, but if we're talking about uploading and 
downloading different files, how often does this happen, and what can we do 
to make it more common?)

> Would it then be better to just push the receipt information via the 
> existing inter-UP QRP infrastructre?

So if I needed receipts for peer X I'd send out a query that would be 
routed via QRP, collecting the receipts?

>How does this affect pseudo-anonymity? 

If the receipts only contain the number of bytes transferred, not the 
details of the files, it doesn't seem to me that it's a major threat to 
privacy - no worse than the information reported to a BitTorrent tracker, 
anyway.

Cheers,
Michael