The stupidity of trying to "fix" DHCPv6

Ricky Beam jfbeam at gmail.com
Mon Jun 13 14:50:09 CDT 2011


On Sun, 12 Jun 2011 09:45:01 -0400, Leo Bicknell <bicknell at ufp.org> wrote:
> In a message written on Sun, Jun 12, 2011 at 01:04:41PM +0200, Iljitsch  
> van Beijnum wrote:
>> Like I said before, that would pollute the network with many multicasts  
>> which can seriously degrade wifi performance.
>
> Huh?  This is no worse than IPv4 where a host comes up and sends a
> subnet-broadcast to get DHCP.

Broadcast != Multicast.  esp. when talking about wireless chipsets.  I've  
yet to find a wifi chipset that didn't completely fuck-up when presented  
with even a low pps of multicast traffic.  Broadcast traffic doesn't seem  
to bother them -- it doesn't attempt to filter them in any way, or really  
pay them any attention.  If I had to guess, the chip firmware is  
individually transmitting multicast packets to each peer; a broadcast  
packet is sent once to all peers.

I've not had any wireless networks disrupted by broadcast traffic -- and  
with Radware load balancers in the network, there are *plenty* of  
broadcasts (ARP).  Just a few 100pps of multicast and the AP fails.  
(linksys, netgear, even cisco... all broadcom crap radios.)

--Ricky




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