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Re: [Vrs-development] Mobile Agents

From: Eric Altendorf
Subject: Re: [Vrs-development] Mobile Agents
Date: Wed, 24 Apr 2002 11:32:51 -0700

I guess I don't fully understand the point....

1: Assuming that all LDS nodes are on the internet, we already have a 
flexible, redundant, extremely reliable routing mechanism, and all nodes 
should be capable of making direct connections to all other nodes.

2: Why is it easier to build a node graph than to keep a table of nodes?  It 
seems to me that in searching the node graph one is building a table of nodes 
anyway.  Being able to build a graph means you can build a table...they're 

3: Now, that being said, there may be a point in having a node graph anyhow, 
if you store bandwidth and ping time information.  For example, if node X has 
to grab some data which is stored on both node Y and node Z, but the node 
graph knows that the average bandwidth between X-Y is much higher than X-Z, 
it would make sense to talk to node Y first.

Any feedback?


On Wednesday 24 April 2002 08:59, you wrote:
> On Wednesday 24 April 2002 13:46, Bill Lance wrote:
> > What do you see as the problem with each LDS
> > maintaining a complete list?  With an open p2p sytem
> > like Guntilla, I could understand this question.  But
> > with a closed, finit cluster like VRS, there shouldn't
> > be all that many node in the cluster to begin with.
> Well there has to be some mechanism where info about the
> joining LDS needs to be propogated across the cluster to
> every other LDS.
> Now, if an LDS is not configured with enough slots for
> all the LDS's that want to be in the cluster, and our
> subscribing LDS contacts that LDS for cluster info, then
> it'll get an incomplete list.
> However, if we can walk the cluster to discover what nodes
> are in the cluster then problem solved.
> This also allows the VRS to be arbitarily large, without
> defining up front how big the VRS will be.
> It's much easier to design and implement and gives many
> additional features and being recursive inherits the
> properties of recursive functions.
> I offer this list of pros and cons for discussion:
> Please change/comment/add/delete things :o)
>                    Pros                      Cons
> NodeWalk:  - Easy to implement
>            - An LDS doesn't have      - Needs a route finding
>              to be connected to         algorithm based on the
>              every other LDS            returned connected graph
>                                         to find remote and not
>                                         directly connected LDS's
>            - Any changes to the VRS
>              structure automatically
>              get propogated
>            - Each LDS can have a      - Some LDS's may only
>              round trip time to each    be reachable via other
>              other LDS in the cluster,  LDS's.  This may only be
>              which means they may opt   a slight problem if you
>              to connect to and route    want to get a message to
>              via the least expensive    an LDS quickly.  Not
>              nodes.                     likely to be a problem...
> Table   :  - Every LDS is directly    - tricky to guarantee
>              visible to every other     the table at an LDS
>              thus direct message        is complete.
>              routing is immediate.
>            -                          - Complicated to engineer.
>                                         An LDS receiving an
>                                         update from one LDS does
>                                         not want to get the same
>                                         update from all the other
>                                         LDS's it is connected to.
>                                       - Loss of network between
>                                         two LDS's means that
>                                         messages cannot pass
>                                         between them.
> Okay brain dead now.
> Any more?

"First they ignore you.  Then they laugh at you.
 Then they fight you.  And then you win."             -Gandhi

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