On Fri, Jun 8, 2012 at 12:48 AM, Karl Auer <[email protected]> wrote: > Yes - whether with ARP or ND, any node has to filter out the packets > that do not apply to it (whether it's done by the NIC or the host CPU is > another question, not relevant here).
It is relevant to the question of the scalability of large L2 networks. With IPv4, ARP presents not only a network capacity issue, but also a host capacity issue as every node expends software resources processing every broadcast ARP. With ND, only a tiny fraction of hosts expend any software capacity processing a given multicast packet, thanks to ethernet NIC's hardware filtering of received multicasts -- with or without multicast-snooping switches. > The original post posited that ND could cause as much traffic as ARP. My > point is that it probably doesn't, because the ND packets will only be > seen on the specific switch ports belonging to those nodes that are > listening to the relevant multicast groups, and only those nodes will > actually receive the ND packets. In contrast to ARP, which is broadcast, > always, to all nodes, and thus goes out every switch port in the > broadcast domain. > > This is pretty much the *point* of using multicast instead of broadcast. I agree.
