Big Temporary Networks

Masataka Ohta mohta at necom830.hpcl.titech.ac.jp
Sun Sep 16 23:42:22 UTC 2012


Nick Hilliard wrote:

>> Thus, protocols heavily depending on broadcast/multicast, such
>> as ND, will suffer.
> 
> ok, you've trolled me enough to ask why ND is worse than ARP on a wavelan
> network - in your humble opinion?

Because, with IPv4:

	1) broadcast/multicast from a STA attacked to an AP is
	actually unicast to the AP and reliably received by the
	AP (and relayed unreliably to other STAs). That is, a
	broadcast ARP request from the STA to the AP is reliably
	received by the AP.

	2) the AP knows MAC and IP addresses of STAs

	3) ARP and DHCP replies are usually unicast

ARP and DHCP usually work.

For an unusual case of ARP for other STAs, collisions do
increase initial latencies, but as refreshes are attempted
several times, there will be no latter latencies.

OTOH, IPv6 requires many multicast received by STAs: RA and NS
for DAD, for example.

Worse, minimum intervals of ND messages are often very large,
which means a lot of delay occurs when a message is lost.

							Masataka Ohta



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