[CUWiN-Dev] G and A and realworld throughput

[David Young]

On Wed, Jul 13, 2005 at 01:52:00PM -0500, Stelios Valavanis wrote:
> ok. that means that even if it's uplink is 20 hops away it's going to connect 
> to the next node over because of fewer packets dropped.

I think we understood each other, but I just want to make sure:

The routers are always sending beacons to their neighbors within radio
range, called "Hellos."  They count the number of Hellos that pass
successfully in each direction.  From that, a router estimates, for each
neighbor, roughly how many times its radio will retransmit a packet before
the neighbor successfully receives it.  This "expected (re)transmission
count" was abbreviated ETX by the researchers at MIT who came up with it.

Routers assign "scores" to every path on the network.  The path's score
is the sum of the ETXs on all of the links on that path.  Paths with
lower scores are preferred.

Dave

-- 
David Young             OJC Technologies
dyoung at ojctech.com      Urbana, IL * (217) 278-3933