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Old February 12th, 2002
maksik maksik is offline
Mutella Developer
Join Date: January 30th, 2002
Location: Germany
Posts: 87
maksik is flying high
Question On Multisegmented Downloading

Hi folks,

in this message (and the thread) I am trying to address mainly people who happen to know thing or two about Gnutella, networking and programming...

The question I have in mind may sound rather simple, but I know there is no an easy answer to in. The question is the following: What could be the optimal strategy (in the realm of Gnutella network) to:

1. split file into the segments
2. distribute the load betweed peers
3. glue segments together

For example, we start downloading from the host A. And in short time we find out that host B happens to have the same file. Now lets assume, host A is fast (what is fast?). Were shall we start sthe second download segment? Because we cannot measure the speed of the host B before we try it. My experience that the fasted downloads I get from hosts dexlaring themselves as 1.44 modems. One alternative would be to maintain the database of the fast hosts, it will at least help with the ones having permanent IPs. What else can be done?

Ok, lets assume, we have made a decision about were to start new segment, and we created lets say 10 segments. So, now, lets imagine, that when all these segments are downloaded, it turns out that 3 of 10 do not match for whatever reason. What shall the client do? That is how one can maintain the tree of alternatives for example given unlimited local storage space for partial files? Or if that soace is limited?

There could be a good point -- to make use of the footprints that are being sent already by some clients in the optional part of the query-reply. Well, according to my experience, I see it only in ~30% replies at the moment, but I want segmented downloads to work now, not next year.

Second objection concerning use of footprints is that for example, because of whatever reason, one bit (or byte) of the particular mp3 file was modified during transmission, and after certain time network gets populated with both original and 'broken' version. For me, as an end user, the chances of getting any of them are pretty equal, and in fact I dont care. Because it's just one bit. And it would be fine, if one part will be taken from the 'damaged' file and another one -- from the original version. But obviously, these files will have different footprints...

May be I've forgotten some other of my questions... buth this should be enough already to initiate a discussion.

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