IP Multicasting
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IP multicasting allows for bandwidth-efficient delivery of information to multiple recipients simultaneously. It has three main components: IP multicast addressing using class D addresses; IP groups identified by multicast addresses; and multicast routing protocols like PIM-SM, PIM-DM, and DVMRP. PIM-SM uses a shared tree rooted at a rendezvous point, while PIM-DM uses source-based trees and prunes unused links. Multicast groups are identified by addresses and receivers must join groups to receive transmissions.
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IP Multicasting
- 1. IP Multicasting Rumesh Eranga Hapuarachchi rehrumesh@Hotmail.com
- 2. Overview • What is multicast • Components of Multicast service • Addressing & groups • Routing protocols
- 3. • 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?
- 4. • Three main components • IP Multicast Addressing • IP Group Management • Multicast routing Components
- 5. • Groups are identified by IP Address range class D address • No Access Control • Sender can be out side of the group • Less Security • Unreliable Multicast Addressing
- 6. • 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
- 7. • 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
- 8. • 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)
- 9. • 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
- 10. Opt In Protocol
- 11. Opt out Protocol
- 12. 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.
- 14. 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.
- 16. 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.
- 17. 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.
- 18. • 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
- 19. 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
Editor's Notes
- Multicast communications refers to one-to-many or many-to-many communications. Unicast Broadcast Multicast
- Class D range – 224.0.0.0 : 239.255.255.255 No Access Control - Every host can join and leave a multicast group dynamically. Every IP datagram send to a multicast group is transmitted to all members of the group. That explains the less security and the ability for the sender to be out side of the group. IP Multicasting only supports UDP as higher layer There is no multicast TCP
- After a user joins, the network builds the necessary routing paths so that the user receives the data sent to the multicast group
- IGMP provides three basic functions for IP multicast networks: • JOIN: An IGMP host indicates that it wants to receive information from (“become a member of”) a multicast group. • LEAVE: An IGMP host indicates that it no longer wishes to receive information from a multicast group. • QUERY: An IGMP router can ask the hosts which groups they are members of. This is done to verify a JOIN/LEAVE request or to look for error conditions. There are 3 version of IGMP 1) IGMPv1:- Hosts can join multicast groups. There were no leave messages. Routers were using a time-out based mechanism to discover the groups that are of no interest to the members. 2) IGMPv2:- Leave messages were added to the protocol. Allow group membership termination to be quickly reported to the routing protocol, which is important for high bandwidth multicast groups. 3) IGMPv3:- Major revision of the protocol. It allows hosts to specify the list of hosts from which they want to receive traffic from
- Opt-in or sparse protocols are designed on the assumption that most subnets in the network will not want any given multicast packet
- In opt-out or broadcast-and-prune or dense protocols, it is initially assumed that every router on the network wishes to receive multicast data, and data is sent to all routers. Routers wishing to remove themselves from the multicast tree must then send a Prune message to the upstream router.
- 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).