Re: [Pyxida-users] Pyxida developer + help

[Eric Chan-T. <dch...@cs...>]

Hi Jonathan and Peter,

First of all, just wanted to say that Pyxida has been working great on
Planetlab for the past 4 months or so. Getting good data and experiments
going well.

However, I do have one question/comment.

Every Pyxida node contains a list of Neighbors (in NCClient) and a list
of Gossip nodes (they are called neighbors in NCManager but I will call
them gossip for now so as not to confuse with the 'real' neighbors in
NCClient). Every 10 seconds, Pyxida will pick a random node (call it A)
from Gossip and send a gossip request (basically asking for rtt,
coordinate, error). But Gossip contains all the nodes in the network.
The comment in the code said that was to avoid Pyxida becoming lonely
and no-one to gossip with, which makes sense.

Once A responds, Pyxida will add A to its Neighbors (if Neighbors does
not contain A) and remove the first element from the Neighbors list.
This seems a little bit odd. Was there any particular reasoning behind
this?  Because it would seem like you're getting the coordinate from
every node in the network eventually.

Thanks a lot,

-Eric

Jonathan Ledlie wrote:
> 
> Your inclination is correct.  See forwarded message.
> 
> -jonathan
> 
> On Apr 9, 2008, at 1:53 PM, ext Eric Chan-Tin wrote:
> 
>> Thank you for the clarification.
>>
>> I've been reading through your published papers and code and I must
>> say I learned a lot about how Pyxida works :)
>>
>> I still have a quick and easy (hopefully) question. Each Pyxida node
>> has a small amount of neighbors and learn about other nodes through
>> other nodes. I am running on about 200 machines, and it seems like all
>> the Pyxida nodes are adding each other to their upNeighbors set.
>> NCClient.java has the MAX_NEIGHBORS set to 512.
>>
>> I wanted to make sure that I am not misreading the code, but shouldn't
>> each Pyxida node keep a small number of neighbors in its upNeighbors
>> set. Else, it will be a lot of updates to send a gossipMessage to all
>> 200 neighbors, and it also means that a Pyxida node has the whole
>> network in its upNeighbors set - that seems wrong. I am inclined to
>> change the value of MAX_NEIGHBORS but wanted to make sure that my
>> understanding is correct first.
>>
>> Thank you,
>>
>> Eric
>>