Re: [DNA] High-level overview of DNA, take 2

[Greg Daley <gregd@research.panasonic.com>]

Bernard Aboba wrote:
> \>    Are there other messages that can be sent that could help? Like NS
>>    queries unicast to known routers?
> 
> This is what DNAv4 does (via unicast ARP), because this enables a
> determination of whether the host has connected to a previously
> encountered router, without ambiguity.
> 
>>    Note: on some links, like wireless ethernet, multicast is
>>    (relatively) "expensive". Would it be better to just send a few
>>    immediate unicast NS (or RS) messages to the routers we know about?
>>    and send a multicast RS only if the unicast fails? Or do both in
>>    parallel?
> 
> DNAv4 does both DHCP and DNA in parallel.  DNAv4 is handled solely via
> unicast ARP, because on some links multicast not only is sent to many
> more hosts, but also is sent at much lower  rate.   For example, with
> IEEE 802.11n, it would be possible to send *a hundred*  unicast packets
> at 100 Mbps at the same cost in expended slots as  one multicast packet
> at 1 Mbps.  This means that in practice a single multicast RS will cost
> more than sending unicast RS or NS messages to all previous routers.

Actually, if the switches monitor multicast groups, the packet will
be sent toward the AP as unicast with the toDS bit set, and won't be
retransmitted over the wireless LAN.  The wireless transmission
therefore can operate at a higher rate available to 802.11n.

Greg