IP multicast, a method of selectively sending messages promoted by an industry consortium of prominent companies, is an up-and-coming technology that will be used increasingly for:
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monitoring: manufacturing and other types of real-time information, sensor equipment or security systems.
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announcements: network time, multicast session schedules, random numbers, keys, configuration updates, etc.
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file distribution and caching: Web site content, executable binaries
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scheduled distribution of audio and video
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push media: news headlines, weather updates, sports scores, etc.
You should make sure that your router and/or switches support multicast, your workstations are configured to join a multicast group and that you have installed any specific applications needed to receive the multicast.
IP Multicasting Transport
The UDP protocol is used for IP multicasting. The multicast address selected is important in allowing network managers to control the way hosts (end devices) join groups and how routers exchange multicast information.
In IP multicasting, each group has a multicast group ID, a set of Class D IP addresses used to specify the destination of a message. The addresses range from 224.0.0.0 to 239.255.255.255. Each multicast IP address can have a number of hosts listening to it. Hosts can belong to a multicast group, and the IP addresses are associated with that group. Each configured device has a multicast IP address that is in addition to its own IP address.
Class D addresses can be classified as follows:
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permanently assigned: addresses in the range 224.0.0.0 to 224.0.0.225, permanently assigned by IANA for certain applications such as routing protocols; for example:
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224.0.0.0 for the base address
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224.0.0.1 for all systems on this subnet
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224.0.0.2 for all routers on this subnet
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224.0.0.4 for DVMRP routers
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nonpermanent: addresses in the range 224.0.1.0 to 238.255.255.255, used for assignment as needed on the Internet
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administered nonpermanent: addresses in the range 239.0.0.0 to 239.255.255.255, reserved for use in private Intranets
