Re: MULTICAST: cannot join a group across the OpenVPN connection. Why?

On Sun, 10 Sep 2006 05:31:50 +0400, Roy Marples <uberlord@xxxxxxxxxx>  
wrote:

> Or that most people here have nfc what multicasting is.
MULTICASTing vs BROADCASTing is (in short):
You broadcast to "all ones" IP address on a segment, i.e. for  
192.168.1.0/24 it is 192.168.1.255,
while multicasts go to imaginary IP address in the special range, in my  
example this is 239.255.20.1

The advantage of MULTICAST is that if noone on a given segment needs|wants  
your data - the data never enters such a segment. When some host decides  
it needs that data it "joins" a multicast group, i.e. informs it's closest  
router it needs to pass the multicasted data into a segment. When the last  
host on a segment decides to "leave a group" - the closest router again  
stops to route multicasted data into a segment.
With broadcasts it is not possible (for the receiving side) to control the  
presense of the data - receive it or not - the sender will flood all of  
your LAN with it's data.
Besides, in IPv6 there will be no conception of BROADCASTs any more, only  
MULTICASTs should be used instead.

Tony.


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