[156366] in North American Network Operators' Group
Re: Big Temporary Networks
daemon@ATHENA.MIT.EDU (Masataka Ohta)
Sun Sep 16 19:44:40 2012
Date: Mon, 17 Sep 2012 08:42:22 +0900
From: Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp>
To: Nick Hilliard <nick@foobar.org>
In-Reply-To: <505626A2.1090700@foobar.org>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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
