[EMAIL PROTECTED] wrote:
>>There are also some nasty interactions between multicast and power
>>saving. To save power, the stations sleep most of the time, wake up
>>occasionally, and poll the server for any queued data. For multicast,
>>you have to either guarantee that all stations wake up at the same time,
>>which is hard, or accept to effectively replicate the multicast packet
>>for each station.
> for multicast, you can assume that all intended receivers are
> "awake" for your application design, but that is not (to my
> understanding)
> an intrinsic component of multicast.
It is merely that each station is required to wake up when
packets to the station are transmitted, regardless of whether
the packets are unicast, multicast or broadcast.
Thus, the amount of power consumption of a station increases
proportional to the number of multicast addresses the station
joins.
It's not a problem if the station is running streaming applications,
which, anyway, consume considerable amount of power.
However, frequently multicast RAs to all-nodes multicast address
are really annoying.
Masataka Ohta
PS
A real difference between unicast and multicast/broadcast of CSMA/CA
wireless link such as 802.11 is that the latter can not be ACKed and
is unreliable.
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