[Blocks-development] comments on the Blocks architecture...

[Ben H. <be...@ex...>]

Hi PG,

> so, servers with < 7 connections always react, while servers
> with 14 connections have a 20% chance of trying to connect.
> The new server should accept on a first-come-first-served
> basis.

Why do you have to many connections?  Did you know that in a truly randomly
connected graph you only need only around 2.5 - 3 connections per node to
guarantee that the network is connected?  You could go for 4 or 5 if you
really wanted to be secure.

> 'File advertisements' are broadcast through out the
> network. Your Blocks application needs to be running
> to see them. When you do a 'search' you are actually
> searching the local list maintained by your Blocks
> application, searches are never broadcast.

Okay, so I guess the point of this is that you encourage
people to remain on the network for longer periods of times
since it increases the number of files that they can see.

When a new client connects do you pass along the index of files
of the clients that it connects to?

How do you track which files have dropped off the network because
those clients left the network?

> Other servers
> then choose to connect to the new server depending on how many
> connections they have, and a PRNG.

What's a PRNG?

Also how do you protect against someone broadcastings a bunch of lies
instead of a real file index?

> Perhaps Michael & Erik's simulator will clarify this.

Neat, I'm writing a simulator too.  To start with I've created
a few classes for creating random graphs and measuring
the connectivity. ...it should be really easy to figure out:
  http://www.exocortex.org/~ben/graphtools_v01.zip

I'm planning on making a multithreaded simulator once I get some time that
will simulate the behavior of clients rather than just a weighted graph.  I
hope to make a visualizer for it a la NetViz:
  http://www.exocortex.org/netviz

Later,
-ben houston
www.exocortex.org/~ben


> -----Original Message-----
> From: Blat Froop [mailto:pet...@ho...]
> Sent: August 15, 2000 9:45 PM
> To: be...@ex...; blo...@li...
> Subject: Re: [Blocks-development] the GRID proposal
>
>
> >From: "Ben Houston" <be...@ex...>
> >To: <blo...@li...>
> >Subject: [Blocks-development] the GRID proposal
> >Date: Tue, 15 Aug 2000 20:35:52 -0400
> >
> >Hi,
> >
> >A few people (Jonathan Byron and Michael Spencer) have mentioned in the
> >last
> >days the BLOCKS project.  I thought that I would drop by and
> tell you about
> >my self organizing protocol that I am developing:
> >
> >Check it out at: http://www.exocortex.org/grid.html
> >
> >And yesterday I developed the start of a growing preference algorithm in
> >order to grow it in a manner that will maintain coherence:
> >http://www.exocortex.org/growing_v01.ppt
> >
> >Although I always talk in two dimensions (planar) all the algorithms are
> >scalable to any dimension greater than one.
> >
> >I'm working full time right now so I do not have time to polish these
> >ideas.
> >Also we are in a very fast moving field (distributed file sharing,
> >distributed applications) so I want to get them out as quickly
> as possible.
>
> Thanks for the input. I dont know much about GNUtella other than
> that it broadcasts searches. I would have thought that it does
> a similar sort of routing as Blocks does with file advertisements
> (searches are not transmitted in Blocknets).
>
> Each Blocks server has upto 16 connections to other servers, and
> when a new file is uploaded, it is given a unique ID (which is
> placed in a blocklist) an advertisement is send to each
> connection. If the advert ID is not blacklisted it is forwarded
> to all connections (apart from the one it came from), and so
> on for upto 6 hops (its a bit like the old flood fill algorithm).
>
> The interconnection logic in blocks is currently quite trivial,
> when a new server connects to the Blocknet, the server it connects
> to advertises the new server to all connections. Other servers
> then choose to connect to the new server depending on how many
> connections they have, and a PRNG.
>
> The formulae works a bit like this...
>
> connect to new server if (16-N)*10 > rand()%100
> where N is the number of current connections.
>
> so, servers with < 7 connections always react, while servers
> with 14 connections have a 20% chance of trying to connect.
> The new server should accept on a first-come-first-served
> basis.
>
> This hasnt been tuned but seems to work well enough for
> small Blocknets. Its unclear what will happen with massive
> Blocknets. Perhaps Michael & Erik's simulator will clarify this.
>
> Blocks also relies on each 'connection' to be indistinguishable
> from all the other ones so that statistical analysis of the
> Blocknet cannot predict the location in the Blocknet of the
> originator of published files. This makes designing Blocknet
> topologies particularly difficult since servers are restricted
> in the amount of information they are allowed to have about
> the topology.
>
> All comments welcome :-)
>
> ttfn
>
> PG.
>
>
>
> ________________________________________________________________________
> Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
>