Sunday, November 29, 2009

Packet Transmissions : Unicast, Broadcast, Multicast and Anycast

100px-Unicast.svgUnicast, ( refers the left diagram ) is a type of packet transmission sent from a source to another destination. In unicast, there is only one sender and one receiver. Most of the application today is Unicast, example HTTP, SMTP, FTP etc. which employ the TCP transport protocol.

Broadcast transmission, (  refers the diagram below ) is a communication method where a piece of packet/information is sent 100px-Broadcast.svgfrom a source to all other destinations within the given address range. Broadcasting normally happen on Layer-2 using ARP ( Address Resolution Protocol )

Multicast, ( refers the diagram right below ) is a transmission technology that delivered the 100px-Multicast.svgsender’s packet or information to a specific groups of recipients. Most common low level protocol to use multicasting addressing is UDP. Unlike broadcast transmission, the recipients only receive the packets if they have previously choose to receive by joining using IGMP. The multicasting is useful when a group of recipients are to receive the same packets from a specific sender over the network at the same time ( refers the diagram below ), it would contribute a significant bandwidth savings and optimizations ( refers the diagram below ). The common usage of the multicasting is IP-television.


Multicast (top) compared with unicast broadcasting (bottom). Orange circles represent endpoints, and green circles represent routing points.

100px-Anycast.svgAnycast, ( refers the left diagram ) is another type of transmission that may not commonly discussed. Anycast transmission is mostly used in the routing purposes where the packets are transmits to the destinations via the “best” routing topology. BGP is one of the anycast transmission where the destination IP address/range is received by the source/sender’s router via difference routes but the will be only one route to be chosen for the packet transmission.

**Pictures source from Wikipedia


Anonymous said...

thanks for your simple n concrete explanation..

btw, is this also applies to ipv6 architecture?

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