Cell Relay Archive

["Vincent BERRUYER" <v.berruyer@silicomp.fr>]

Hi,

Can someone explain the way multicast are managed using LANE services ?
I suppose they are sent to the BUS which will broadcast them to its LEC.
Is there any use of the ATM point to multipoint capabilities for IP
multicasting ?

As far as I know (correct me if I'm wrong) an IP multicast address (class D)
is composed of "1110" followed by a 28-bit multicast group ID.
This IP address is then mapped into an Ethernet (IEEE-802) multicast
address (if I remember the low-order 23 bits of the IP multicast group
ID into the low-order 23 bits of the Ethernet address).
Then a multicast packet received by the BUS and broadcasted to all its
LEC (using the correct multicast Ethernet address) would only concern
the LECs of the multicast group.

If this is the way multicast are managed by LANE services, it seems strange
than in an ATM network with point to multipoint capabilities, IP multicast
are broadcasted !!

Thanks.
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