The stupidity of trying to "fix" DHCPv6

Owen DeLong owen at delong.com
Tue Jun 14 03:00:22 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.)
> 
> --Ricky

You would need an AWFUL lot of hosts for this to add up to a few 100pps (or even 10pps) of multicast
traffic.

Owen





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