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

Polychronis Ypodimatopoulos ypod at mit.edu
Fri May 9 17:30:40 EDT 2008

Bill Mccormick wrote:
> It does look like the NM code will select APs over mesh...   I bet this
> plays havoc with IP changing between link local addresses and DHCP
> addresses.

This is partly because of the scalability limitations of the existing 
collaboration model in a simple mesh. However, I think we can greatly 
improve situation in a simple mesh scenario and that may simplify the 
decisions that NM needs to make.

> Did you expect over half of the packets in your data file to be
> broadcasts?  Specifically 11754 out of 21587 packets were sent to the
> broadcast address.

This is true because all bulk traffic is sent over broadcast _and_ is 
reliable. Sounds weird? Let me provide a brief explanation. All bulk 
data traffic (by "bulk" I refer to traffic that is _potentially_ 
interesting to all nodes, such as profiles, files etc) is sent to the 
broadcast address, but the mac address of the node that originally 
requested the data (or the node to which this data is actually meant 
for) is added in the actual payload, so only one will be replying with 
acks to the sender (which are necessary to ensure reliability), but all 
other nodes will be receiving the data too because it's sent to broadcast.

This actually happens anyway on your network interface, so this scheme 
imposes _no_ additional cost in terms of traffic, other than moving the 
decision of whether a frame is meant for the current host to a higher 
layer. This scheme allows sizeable bandwidth savings 
especially in dense wireless networks.


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

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