Multicast packets allow a device to send data to a group of nodes within the network. Thread makes use of the Multicast Protocol for Low-Power and Lossy Networks (MPL). With MPL implementations networks can communicate using low-power and lossy links with widely varying topologies. Thread defines a set of Mesh-Local scopes boundaries for interfaces participating in the same Thread Network. Multiple Mesh Link Establishment (MLE) packets require the use of multicast packets to establish the link costs or for device synchronization. All Thread interfaces must subscribe to a Link-Local All-Nodes multicast address (FF02::1) and Realm-Local all-nodes multicast address (FF03::1). Interfaces operating like Router, REED (Router Eligible End Device), or Border Router must subscribe to the Link-Local All-Routers multicast address (FF02::2) and a Realm-Local all-routers multicast address (FF03::2). Routers transmit MLE Advertisements to the Link-Local All Nodes multicast address (FF02::1) with a variable interval (see Trickle algorithm) from 0 to 32 seconds. The Realm-Local scope addresses are mostly used for application purposes.