The stupidity of trying to "fix" DHCPv6

Joel Jaeggli joelja at bogus.com
Mon Jun 13 15:57:32 CDT 2011


On Jun 13, 2011, at 12:50 PM, Ricky Beam wrote:

> 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.)

by default the multicast rate is at the lowest supported rate on the ap which negatively impacts the performance of everything else.

> --Ricky
> 





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