[CUWiN-Dev] notes on TDV

[David Young]

Some routers at TDV are spending about 50% of their CPU time in the
operating system, leaving very little CPU headroom for forwarding, HSLS,
etc.  I believe we owe the system overhead to the density of the network;
every node can hear every other, so every node is bombarded by HSLS
packets.  There are a few things we can try to get the CPU usage down:

        1 Turn off IPv6 (easily halves the number of packets).

        2 Scale transmit power (sysctl -w hw.ath0.tpscale=4) to control
          nodal degree and interference.

        3 Figure out how to adjust receive sensitivity to filter
          out transmissions from distant nodes.

Matt and I noticed that the diversity sysctl is turning back on
(hw.ath0.diversity = 0 -> 1) when the ath0 is brought up.  I.e., we
need to put '!/sbin/sysctl -w hw.$int.diversity=0' at the bottom of
ifconfig.backhaul.tmpl.  I don't know if this is making any practical
difference, since we have forced the interfaces to use just one antenna
for transmit and receive, and those settings are not reset when we bring
the interface up.

Matt tells me that dhcpselect is not working right on gateways.  If the
DHCP server is not available when the node boots, dhcpselect may or
may not detect an Internet connection when the DHCP server starts.
Sounds like a regression in dhcpselect.

Dave

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