Sender Initiated Multicast (SIM)
Sender Initiated Multicast (SIM) is a point-to-multipoint multicast mechanism. SIM will not replace the existing multicast protocol, but will be a subset of entire multicast protocol suite. Its design goals are to gain more simplicity than the traditional IP multicast and to gain less header-processing overhead than the Xcast protocol. It eliminates the cost of allocating global multicast address, by routing packets according to receiver unicast addresses attached to packet headers. Access control can be introduced before, members of a receiving group are explicitly specified by the sender. A group is identified by the combination of sender's unicast address and a multicast group address. The key feature of SIM is in its Preset mode, which can lessen the costs of route lookups and provides cost- efficient packet forwarding by using a SIM Forwarding Information Base (FIB) maintained on routers. Moreover, a SIM tunnel will be automatically created between two routers that act as multicast branching points. Therefore, SIM can gain scalability by maintaining FIB entries only on the branching routers. In this document, we describe SIM including its delivery models, SIM FIB operations, the formats, and security considerations.