IP multicast is a routing technique that sends IP traffic from one or more data sources to multiple destinations. Thus, it can be a point-to-multipoint( P2MP) connection or a multipoint-to- multipoint connection.
In IP multicast connections, the IP data packets identified as multicast by the IP address with Class-D address are sent to a multicast group. In the IP address range and in IPv4, specially reserved multicast address blocks are available for IP multicast in the address range from 184.108.40.206 up to 220.127.116.11. InIPv6, these are all addresses beginning with FF00::/8. IP multicast works with multicast addresses consisting of IP addresses and pseudo MAC addresses( PMAC) assigned to multicast groups. In IP multicast, the pseudo MAC addresses have the address space 01-00-5e-00-00 to 01-00-5e-7f-ff-ff.
IP multicast technology forms the basis for real-time applications over multipoint links, such as web conferencing or streaming services with multi-streaming or live streaming. Unlike unicast, multicast can reduce congestion in the network because the IP data packets are not sent individually between the sender and many recipients, but only once, targeted at all participants. To ensure quality of service( QoS), IP multicast must use protocols that exhibit real-time behavior, such as the Realtime Transport Protocol( RTP), the Realtime Streaming Protocol( RTSP), the Resource Reservation Protocol( RSVP) and several others. In addition to the hardware and software that support IP multicast, routing protocols such as the DVMRP protocol, the MOSPF protocol, or Protocol Independent Multicast( PIM), as well as security features in the network, must be considered.
IP multicast is described in RFCs 1112, 4604 and 5771.