Multicast over LANs & Scoping
Multicasts are flooded across MAC-layer bridges along a spanning tree
- LAN NICs must be specifically programmed to filter multicasts on behalf of the end station
- But flooding may steal sending opportunity for nonmember stations which want to transmit
Scope: How far do transmissions propagate?
Implicit scoping: Reserved Mcast addresses => don’t leave subnet. Also called “link-local” addresses