Protocol-Independent Multicast: Difference between revisions

Revision as of 13:55, 31 October 2020

Revision as of 03:12, 28 January 2021

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There are four variants of PIM:

* '''PIM Sparse Mode''' (PIM-SM) explicitly builds unidirectional shared trees rooted at a ''rendezvous point'' (RP) per group, and optionally creates shortest-path trees per source. PIM-SM generally scales fairly well for wide-area usage.<ref>{{cite web |url=https://technet.microsoft.com/en-us/library/bb742462.aspx |title=PIM-SM Multicast Routing Protocol |publisher=[[Microsoft]] |accessdateaccess-date=2014-03-26}}</ref>

* '''PIM Dense Mode''' (PIM-DM) uses [[dense multicast]] routing. It implicitly builds shortest-path trees by flooding [[multicast]] traffic ___domain wide, and then pruning back branches of the tree where no receivers are present. PIM-DM is straightforward to implement but generally has poor scaling properties. The first multicast routing protocol, [[DVMRP]] used dense-mode multicast routing.<ref>{{cite web |url=http://www.multicasttech.com/faq/ |title=Frequently Asked Questions (FAQ) File for Multicasting |publisher=Multicast Tech |archiveurlarchive-url=https://web.archive.org/web/20110614164202/http://www.multicasttech.com/faq/ |archivedatearchive-date=2011-06-14}}</ref> See the PIM Internet Standard RFC 3973.

* '''Bidirectional PIM''' (Bidir-PIM) explicitly builds shared bi-directional trees. It never builds a shortest path tree, so may have longer end-to-end delays than PIM-SM, but scales well because it needs no source-specific state.<ref name="Cisco Multicast"/>{{rp|70-73}} See Bidirectional PIM Internet Standard RFC 5015.

* '''PIM Source-Specific Multicast''' (PIM-SSM) builds trees that are rooted in just one source, offering a more secure and scalable model for a limited number of applications (mostly broadcasting of content). In SSM, an IP datagram is transmitted by a source S to an SSM destination address G, and receivers can receive this datagram by subscribing to channel (S,G). See informational RFC 3569.

PIM-SM is commonly used in [[IPTV]] systems for routing multicast streams between [[VLAN]]s, [[Subnetwork|Subnets]] or local area networks.<ref>{{cite web |url=https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-Y.Sup16-201202-I!!PDF-E&type=items |title=Supplement on guidelines on deployment of IP multicast for IPTV content delivery |publisher=[[ITU-T]] |accessdateaccess-date=2014-03-23}}</ref>

==Versions==

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==Sparse mode==

'''Protocol Independent Multicast - Sparse-Mode''' ('''PIM-SM''') is a [[protocol (computing)|protocol]] for efficiently [[routing]] [[Internet Protocol]] (IP) [[packet (information technology)|packets]] to [[multicast]] groups that may span wide-area and [[inter-___domain]] internets. The protocol is named ''protocol-independent'' because it is not dependent on any particular unicast routing protocol for topology discovery, and ''sparse-mode'' because it is suitable for groups where a very low percentage of the nodes (and their [[router (computing)|router]]s) will subscribe to the multicast session. Unlike earlier dense-mode multicast routing protocols such as [[DVMRP]] and [[dense multicast]] routing which flooded packets across the network and then pruned off branches where there were no receivers, PIM-SM explicitly constructs a tree from each sender to the receivers in the multicast group.<ref name=CiscoPIM>{{citation |url=http://www.cisco.com/en/US/docs/switches/lan/catalyst3750x_3560x/software/release/12.2_53_se/configuration/guide/swmcast.html |title=Configuring IP Multicast Routing |publisher=[[Cisco Systems]] |accessdateaccess-date=2013-12-06}}</ref>

===Multicast clients===

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==External links==

*{{cite web |url=http://www.multicast.org.uk/nws34/slides/5a-IP-PIM-Networkshop-09.pdf |title=PIM Routing |author=Gorry Fairhurst |date=2006 |accessdateaccess-date=2011-12-06 |url-status=dead |archiveurlarchive-url=https://web.archive.org/web/20111228072037/http://www.multicast.org.uk/nws34/slides/5a-IP-PIM-Networkshop-09.pdf |archivedatearchive-date=2011-12-28 }}

* [http://www.rfc-editor.org/rfc/rfc4601.txt Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification (Revised)]

* [http://www.ietf.org/rfc/rfc3569.txt An Overview of Source-Specific Multicast (SSM)]