On Wed, Sep 19, 2012 at 11:33 AM, Sean Harlow <sean@seanharlow.info> wrote:
On Sep 19, 2012, at 04:25, Masataka Ohta wrote:
As I already stated, DHCP discover/request from STA to AP is unicast.
This didn't sound right, so I decided to test. With the three clients available to me (laptop running OS X 10.7.4, phone running Android 4.0, and iPod running iOS 4.1.2) all client->server DHCP was broadcast, as well as server->client NACKs. Server->client offers and ACKs were unicast.
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. In the return direction (AP to station) broadcast and multicast packets are not subject to error recovery while unicast packets are. Hence the the DHCPv4 server->client unicast offers and acks pass reliably while IPv6's equivalent multicast ICMPv6 router advertisements do not. On Wed, Sep 19, 2012 at 5:54 PM, Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp> wrote:
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 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 is a broadcast packet because the switch doesn't have the address in its MAC table. The packet is flooded out all ports but its not a broadcast packet. A layer 2 packet was unicast, multicast or broadcast moment I attached the appropriate destination MAC. The exact handling on a particular segment of the layer 2 network, while important in other contexts, is irrelevant to the designation unicast, multicast or broadcast. On Wed, Sep 19, 2012 at 3:26 AM, Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp> wrote:
The only thing operators have to know about IPv6 is that IPv6, as is currently specified, is not operational.
No offense, but it is not for you or I or Owen Delong to declare that IPv6 is or isn't operational. Operators of individual networks can and will decide for themselves whether and when IPv6 is sufficiently operational for their use. Your observation about IPv6's equivalent of an ARP reply using multicast so that it misses wifi's layer 2 error recorvery (and thus performs poorly compared to IPv4) was of value. Got any more or are we ready to move on? Regards, Bill Herrin -- William D. Herrin ................ herrin@dirtside.com bill@herrin.us 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004