On Thu, 2012-06-07 at 16:42 -0400, Ricky Beam wrote:
On Wed, 06 Jun 2012 17:17:37 -0400, Karl Auer wrote:
a) DAD only happens when an IPv6 node is starting up. ARP happens whenever a node needs to talk to another node that it hasn't seen in while.
DAD is a special case of ND. It happens every time the system selects an address. (i.e. startup with non-SLAAC address, and when privacy extensions generates an address.)
Er - OK. I should have said "happens when an address is assigned to an interface". It is still, however, way less traffic than ARP, which was my point. Possible exception - a network where everyone is using privacy addresses.
b) DAD only goes to solicited node multicast addresses
This assumes a network of devices that do multicast filtering, correctly.
Yes, it does. It assumes a properly provisioned and configured IPv6 network. While that may not be common now, it will become more common. And it is a self-correcting problem - people who don't want lots of noise will implement their networks correctly, those who don't care will do as they wish. No change there :-) BTW, I'm assuming here that by "multicast filtering" you mean "switching that properly snoops on MLD and sends multicast packets only to the correct listeners".
c) Similarly, ND (the direct equivalent of ARP) goes only to solicited node multicast addresses, ARP goes to every node on the link.
Effectively the same as broadcast in the IPv6 world. If everyone is running IPv6, then everyone will see the packet. (things not running ipv6 can filter it out, but odds are it'll be put on the cable.)
On this point I think you are wrong. Except for router advertisements, most NDP packets are sent to a solicited node multicast address, and so do NOT go to all nodes. It is "the same as broadcast" only in a network with switches that do not do MLD snooping.
So I'm not sure how DAD traffic would exceed ARP traffic.
I wouldn't expect it to.
Nor would I - which was the point of my response to an original poster who said it might. Regards, K. -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Karl Auer (kauer@biplane.com.au) http://www.biplane.com.au/kauer GPG fingerprint: AE1D 4868 6420 AD9A A698 5251 1699 7B78 4EEE 6017 Old fingerprint: DA41 51B1 1481 16E1 F7E2 B2E9 3007 14ED 5736 F687