Big Temporary Networks

Masataka Ohta mohta at necom830.hpcl.titech.ac.jp
Thu Sep 20 01:24:03 UTC 2012


William Herrin wrote:

> I think Masataka meant to say (and said previously) that the DHCP
> request from the wifi station is, like all packets from the wifi
> station to the AP, subject to wifi's layer 2 error recovery. It's not
> unicast but its subject to error recovery anyway.

Mostly correct.

But, as I already wrote:

	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.

Because of hidden terminals, L2 broadcast/multicast is transmitted
only from AP.

>> However, at WiFi L2, it is first unicast to AP and then broadcast
>> by the AP.
> 
> Your use of nomenclature is incorrect. It'd be like saying my ethernet

Ethernet?

> card unicasts a packet to the switch and then the switch broadcasts it
> out all ports. Or like saying that a packet with an explicit MAC
> destination

Do you know MAC header of 802.11 contains four, not just source
and destination, MAC addresses?

Because of hidden terminals and because of impossibility of
collision detection, WLAN is a little more complex than your
guess.

> No offense, but it is not for you or I or Owen Delong to declare that
> IPv6 is or isn't operational.

A single counter example is enough to deny IPv6 operational.

> whether and when IPv6 is sufficiently
> operational for their use.

The scope is not "their use" but "as a protocol for the entire
Internet".

							Masataka Ohta



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