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Overview
• What is multicast
• Components of Multicast service
• Addressing & groups
• Routing protocols
• IP Multicast is a bandwidth-conserving technology that reduces traffic by simultaneously delivering a single stream of information to thousands of corporate recipients and homes.
What is multicast?
• Three main components
• IP Multicast Addressing
• IP Group Management
• Multicast routing
Components
• Groups are identified by IP Address rangeclass D address
• No Access Control
• Sender can be out side of the group
• Less Security
• Unreliable
Multicast Addressing
• Set of receivers for a multicast transmission
• Group identified by the Multicast Address
• To receive multicast transmissions, User must join and become a member of a group.
Multicast Groups
• Internet Group Management Protocol (IGMP)
• Protocol Independent Multicast Sparse Mode (PIM-SM).
• Protocol Independent Multicast Dense Mode (PIM-DM).
• Distance Vector Multicast Routing Protocol (DVMRP).
• Bi-directional PIM (BIDIR-PIM).
Multicast Routing
Protocols
• Interested receivers send Membership-Report to nearest multicast router
• Upon receiving Membership-Report Multicast Router starts sending traffic to that subnet
• Router periodically send MembershipInternet Group Management
Protocol (IGMP)
• There are few most important properties
• Whether they use opt-in or opt-out routing protocols.
• Whether they use source-based or shared trees.
• The methods they use to find the upstream router.
Properties of Routing protocol
Opt In Protocol
Opt out Protocol
Source Based Tree Protocol
• Source based tree protocol build a separate tree for each source that send data to multicast group.
• Router wishing to join the multicast group must specify both the source and the group of the multicast data.
• The advantage of sourced based tree protocol are that multicast data path are always efficient and they benefit from a simpler configuration.
Source Based Tree Protocol
Shared Based Tree Protocol
• Shared tree protocol build a single tree is used for all source for a multicast group.
• The tree is rooted at some selected node called rendezvous point.
• The root of each shared multicast tree must be selected in some manner such as pre configuration.
Shared Based Tree Protocol
PIM- Spare Mode
• PIM-SM is opt-in multicast routing protocol.
• PIM-SM by default used shared based trees with the trees rooted at a router called Rendezvous point (RP) for a group.
• Data is send to an (RP) via encapsulation in PIM control message sent by unicast.
PIM- Dense Mode
• PIM-DM is opt-out multicast routing protocol.
• PIM-DM uses source-based trees to distribute data.
• It assumes that the receivers for any multicast group are distributed densely.
• Links on which the data is not required are removed from the tree using PIM Prune messages.
• PIM-DM support source based tree.
• 3 main components in IP Multicasting
• Multicast addressing, pros and cons
• What are multicast groups and identification
• Routing protocols• IGMP 1,2,3
• PIM-SM
• PIM-DM
• DVMRP
• BIDIR-PIM
Summery
References
• Wikipedia. “IP multicast” wikipedia.com [Online]. Available :
http://en.wikipedia.org/wiki/IP_multicast
• The Linux Documentation Project . “Multicast Explained”
tldp.com [Online]. Available :
http://www.tldp.org/HOWTO/Multicast-HOWTO-2.html
• Chuck Semeria and Tom Maufer (2013, Aug.
13). “Introduction to IP Multicast Routin”. NC States
University [Online]. Available:
www4.ncsu.edu/~rhee/clas/csc495j/ip-multicast-part1.pdf
