Multicast 多播

Abstract

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• A Network Protocol that allows a single source to send Data to multiple receivers simultaneously
• Similar to Broadcasting, but more efficient because data is is only sent once, and then replicated by network to reach all receivers
• When a source sends a multicast packet, it uses a Multicast IP address as the destination address. The network then replicates the packet and sends it to all of the receivers in the Multicast Group

Common Use Cases

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Software Update

• Used to distribute software updates to multiple devices simultaneously

Video Conferencing

• Send audio and video streams to multiple participants in a video conference

Online Gaming

• Send game state updates to multiple players simultaneously

Terminologies

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Multicast IP address

• IP Address in the range 224.0.0.0 to 239.255.255.255

Multicast Group

• A logical group for receivers who are interested in receiving Data from sender
• Joining is done by sending an IGMP (Internet Group Management Protocol) join message to the network
• Once a receiver has joined a multicast group, it will continue to receive all of the packets that are sent to that group, until it leaves the group