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