Re: [Help-gnunet] Block order

[Christian Grothoff]

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On Saturday 01 February 2003 12:11 am, Tom Barnes-Lawrence wrote:
> OK, I just remembered another one:
>
>  Many file types have file-magic somewhere at the beginning.
>
>  Is there some reason, either technical or to do with keeping
> everything anonymous, for not making the first block or 2 of
> a file more likely to be downloaded earlier?

How would you do this? Currently, the peers essentially request a block at 
about the time where they know what to ask for. The network returns results 
in a mostly random fashion, so it's possible for any block to come back at 
any time. We could give slightly higher priorities for blocks at the 
beginning of the file or make those requests "jump" the queue (if there is a 
queue), but that would not ensure that you get those blocks back first. In 
fact, some versions ago we introduced a patch that would specifically 
randomize the order to avoid the problem that too many peers just download 
the first 5 blocks and then give up on the download, giving those blocks a 
very good distribution on the network at the cost of the other blocks.

>  Or is whichever part of the system (either insert or download)
> already geared up to behave this way and I've just not noticed?

Well, we do a little bit in this direction by processing the sub-blocks of an 
IBlock in the order of 0 to 24 in the for loops... :-)

>  Oh, and are the keywords case sensitive, and what characters are valid?

Keywords are case sensitive and you can use any character (other than '\0'). 
The difficult part would of course be to convince your shell (or gui) to pass 
"any charater" to GNUnet.

Christian
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