I have a L2 Managed 1Gbps switch with IGMP snooping (the switch I'm testing with is a TP-Link TL-SG3216). I have several identical devices (these are embedded devices that we are developing) attached to the switch, and this system is NOT connected to any other network.
While all devices send some data to all other devices, most of the time they spend in pairs (these pairs change with time). When paired, they utilise close to the full-bandwidth of the connection in one direction. I now have a situation where there are cases in which a device has to send the 1Gbps data stream to two or three devices at once: I need multicasting.
If I were to broadcast this data the other ports would become congested and would effectively prevent other pairs from effectively communicating?
The only way that I know of to achieve multicasting (as opposed to broadcasting) on a switch such as this, is via IGMP snooping (PLEASE CORRECT ME IF THIS STATEMENT IS INCORRECT).
IGMP snooping requires a device to act as a multicast router in respect to IGMP. I have added IGMPv2 capabilities to the devices: whichever device on the switch has the lowest MAC address becomes the multicast router.
This system works: devices can join and leave groups as they wish, and the multicast data is correctly directed by the switch. So far so good.
In IGMP the multicast router is a member of EVERY multicast group, and receives all data sent to any multicast address. Once more than one multicast group is established in this network then the full 1Gbps data streams from multiple devices is sent to the multicast router completely overrunning the link from the switch resulting in huge packet loss. The device acting as multicast router must also perform its regular (non-router) duties.
Is there a way for the multicast router to not be a member of a multicast group, or at least not be sent every packet? I've been told by others that this is not possible.
Is there a different solution to achieving multicasting on this switch?
It appears the solution is to use a different switch: one with a multicast querier built in. This avoids the problem of there being insufficient bandwidth for a multicast router.
Will a switch with multicast querier suffer from the same problem as the multicast router in the original system? Specifically that all multicast frames (not just the IGMP reports) are sent to the multicast router (in this case the switch querier), and with the high traffic the querier will be swamped.