I made some test on VLAN, which were not really good.
Let's suppose that I have 2 switches, fully ~"busy"... all ports in full
activity and with NO VLAN. One of the switch has the access to internet,
via a router and modem.

A small LAN whose gateway is a five port router has a workstation
connected like so,
 Workstation <-> switch <-> router ( <-> rest of the LAN )
I add another switch, i.e.

I believe this is not off-topic, as IGMP now is a part of almost every
decent Layer-2 switch. My question is is there a default behavior for the
switch when IGMP is enable and there is a steady multicast traffic from a
router, but there are no Join messages coming from hosts ...

I have been looking for exponential backoff algorithm
and landed in the below link -
http://en.wikipedia.org/wiki/Exponential_backoff
The above link conveys 51.2 μs as an 'example'.