> netdev experts, > > When there is a L2 switch underneath the network interface a flooding of > multicast at the bridge interface results in one copy of this going through > each > of the slave resulting in multiple multicast packets reaching the underlying > switch.
Yes, this is something Florian, Vivien and i have discussed. We don't yet see a way around it. Neither the Marvell or Broadcast switches have a mechanism to say: Send this frame out of this list of interfaces. All we can do is send it out a single interface. Even if we could direct a single frame out multiple interfaces, we still have the problem of how to teach the bridge about this, in a clean and elegant fashion. Overall, this seems like a hard problem. Since it is a hard problem, implementing IGMP snooping first would make sense. Don't forward the packet out a port unless you know there is somebody interested in it. The swichdev parts of IGMP snooping are in place, we just need to continue them down into DSA. > L2 switch also duplicates the multicast packet on each egress port as done > in software bridge. This is undesirable as it reduces the available bandwidth > to > half when multicast packets are involved. Once you have a DSA driver, the switch will not do this replication. So you will gain something there. Andrew