The stupidity of trying to "fix" DHCPv6

Owen DeLong owen at delong.com
Wed Jun 15 00:40:56 CDT 2011


On Jun 14, 2011, at 5:50 PM, Ricky Beam wrote:

> On Tue, 14 Jun 2011 18:16:10 -0400, Owen DeLong <owen at delong.com> wrote:
>> The point of /64 is to support automatic configuration and incredibly sparse host addressing.
>> It is not intended to create stupidly large broadcast domains.
> 
> Several IETF (and NANOG) discussions say otherwise.  While current hardware doesn't handle thousands of hosts, the protocol was designed for a future where that's not true. (there's a future where *everything* is network enabled... microwave oven, doorbell, weed whacker, everything.)
> 
Sure, but, that future still doesn't need stupidly large numbers of hosts on a common link.

>> A /22 is probably about the upper limit of a sane broadcast domain, but, even with a /22
>> or 1022 nodes max, each sending a packet every 10 seconds you don't get to 100s of PPS,
>> you get 102.2pps.
> 
> As I said, DHCP isn't the only source of traffic.  Setup a 1000 node network today (just IPv4), and you will see a great deal of broadcast traffic (unless those nodes aren't doing anything.)  With IPv6, it's all multicast (v6 doesn't have a "broadcast address") hinged on switches filtering the traffic away from where it doesn't need to be.  The all-too-common Best Buy $20 white box ethernet switch does no multicast filtering at all.  Pretty much all wireless hardware sucks at multicast - period.  These are not things that can be fixed with a simple software update... if the silicon doesn't do it, *it doesn't do it*.

Depends on a number of factors. Yes, there are lots of issues. However, they aren't caused
by the small number of additional packets from DHCP.

Owen





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