12.13.06
Posted in Essays, multicast/anycast at 9:14 pm by Sailesh Kumar
Any communication process can be divided into one of the three main categories, unicast, multicast, and broadcast communication. In unicast, messages are sent from one source to one destination; the message may traverse through several intermediate nodes. In broadcast, messages are sent from one source to all destinations which have physical connectivity to the source. Multicast is the process of sending the message from a single source to a subset (containing two or more hosts) of all physically connected destinations. When messages have to be sent from one source to multiple destinations, multicast is generally a much more efficient mode of communication than simply unicasting the message to all destinations. Multicast is efficient because the message need not be replicated for every destination; replication only occurs when the message gets close to the destination. Thus, the links which are close to the source do not require large bandwidth, which is otherwise needed if the same message is unicasted multiple times. Clearly, multicasting has several applications, some of which are multi party video conferencing, broadcasting information to a large number of users, real-time video distribution, etc.
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12.03.06
Posted in Essays, multicast/anycast at 9:44 pm by Michael Roche
IP multicast is a must for the Internet. It provides many advantages over a plain unicast network. With demand growing toward more streaming media, IPTV, and video conferencing applications, multicast becomes more and more of a necessity. There are many advantages that multicast offers to these type of applications. The infrastructure for IP multicast already exists. It is supported by Ethernet and many multicast protocols are already implemented in routers.
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Posted in Essays, multicast/anycast at 9:44 pm by mbecchi
A multicast communication service sends packets from a source to a set of destinations, also called multicast group. The basic underlying idea is to propagate the packets into the network so to reduce the bandwidth involved. If, for instance, a packet has to be sent from a source on ISP x to N recipients connected to another ISP y, then a unique copy of the packet will be first sent from ISP x to ISP y, and then ISP y will locally dispatch N copies of the packet to the interested recipients. In a more general scenario a multicast dissemination tree, that is, a minimum spanning tree rooted at the sender, will be used in order to determine how a multicast packet will be propagated in the network. This solution will involve a degree of bandwidth consumption which is far less than simply having many unicast transmissions between the sender and every recipient.
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