[sugar] 65-node simple mesh test (and counting... ;-)

Polychronis Ypodimatopoulos ypod at mit.edu
Fri May 9 16:18:46 EDT 2008

Hi Greg,

Greg Smith (gregmsmi) wrote:
> Thanks for sharing the results. Did you use a wireless AP or active
> antenna? 

No access points or active antennas were involved. This is a simple mesh 
network test.

> If you can include a few details on that it will help. Can you
> also include the XO build # and XS build and config if relevant?

build 703

> Would you say that this test passed? That is, can we recommend that
> schools use the chat activity with one chat session which all join?

Cerebro is software under development and as such it has bugs, but I'm 
confident that it can easily handle 50-node, simple mesh networks (in 
terms of presence/profile information) and if activities use Cerebro for 
their data transport and sharing needs, then there is proof 
(http://cerebro.mit.edu/images/Comparison1.png) that Cerebro will always 
beat any TCP-based approach (even if access points/active antennae are 

Like Morgan said, Cerebro is not in build yet but we are examining 
various integration plans. The chat activity mentioned should not be 
mistaken for the Chat-activity on the XO. The former is an offshoot from 
the latter that only users Cerebro for collaboration/data exchange.

> Lastly, can you tell us what kind of testing time and focus you will
> have in the near future? I believe there is a mesh test lab coming up at
> Nortel in Ottawa as well. Any feedback on test capacity and plans there
> is appreciated too.

I'm not familiar with the testbed in Ottawa. The plan is to expand the 
mesh test to 100 nodes and bring down the time it takes for the network 
to converge even further. Currently it's linear with the number of nodes 
and I'll experiment with some ideas on how make it completely constant 
and negligible! Also, I plan to make Cerebro more socially-aware 
(permanently cache profiles of friends, share "bookmarks" of friends as 
a "friend recommendation" process) and enhance its security (already 
collaborating with another team of MIT students on this).

> I ask because there is recent feedback on mesh issues from a teacher at
> Lambayeque, Peru http://wiki.laptop.org/go/Lambayeque#Inconvenientes and
> a teacher in Uruguay has asked about supported Mesh features too. The
> Lambayeque page says: they wish they knew in advance that Acoustic
> Measure Activity would not work with 6 groups of two students each.
> That's mostly an issue with activity design and our communication about
> what activities support but it does raise a good test case (6 groups of
> 2 sharing a single activity).

As you can imagine, 6 groups of 2 kids is a pretty trivial case in terms 
of networking ;-) given that there is not an overwhelming amount of 
traffic involved. I 'll try to get in touch with Ben (author of Acoustic 
activity) to discuss this issue. As always, feedback from teachers and 
children is extremely welcomed! Unfortunately, I cannot read the 
'Lambayeque' wiki page.

> I think both (Peru and Uruguay) teachers can help define meaningful mesh
> use cases which will be applicable in many schools. I want to set the
> right expectation on our capacity before I ask them to spend a lot of
> time working with us. 

Would you like to setup a few use cases that I could put to the test and 
explore our limits?
I would like to shift my focus to make Cerebro more activity-friendly 
and examine alternative use cases.

Thanks for the feedback,


Polychronis Ypodimatopoulos
Graduate student
Viral Communications
MIT Media Lab
Tel: +1 (617) 459-6058

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