Protocol-Independent Multicast: Difference between revisions

Revision as of 21:34, 27 May 2017

Revision as of 21:57, 27 May 2017

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[[image:IGMP basic architecture.png|thumb|400px|Example of a multicast network architecture]]

'''Protocol-Independent Multicast''' ('''PIM''') is a family of [[multicast]] [[routing protocol]]s for [[Internet Protocol]] (IP) networks that provide one-to-many and many-to-many distribution of data over a [[LAN]], [[Wide area network|WAN]] or the [[Internet]]. It is termed ''protocol-independent'' because PIM does not include its own [[network topology|topology discovery]] mechanism, but instead uses routing information supplied by other [[routing protocol]]s. PIM is not dependent on a specific unicast routing protocol; it can make use of any unicast routing protocol in use on the network. PIM does not build its own [[routing tables]]. PIM uses the unicast [[routing table]] for [[reverse path forwarding]].<ref name="Cisco Multicast">{{citation |url=https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/15-2_2_e/multicast/configuration_guide/b_mc_1522e_3750x_3560x_cg/b_mc_3750x_3560x_chapter_011.html |title=IP Multicast Routing Configuration Guide |publisher=[[Cisco]] |access-date=2017-05-27 |page=56-57}}</ref>{{rp|56-57}}

There are four variants of PIM:

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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]] |accessdate=2014-03-23}}</ref>

==Versions==

There are two PIM versions. The versions are not directly compatible though may coexist on the same network. Network equipment may implement both versions. PIMv2 has the following improvements over PIMv1: A single RP is used per group. RP discovery is accomplished by a '''Bootstrap Router''' (BSR). Groups are either sparse or dense mode; Interfaces can be either. General improvements to protocol flexibility and efficiency.<ref name="Cisco Multicast"/>{{rp|59}}

==Sparse mode==