1 / 31

Multicast

Multicast. Outline Multicast revisited Protocol Independent Multicast - SM Future Directions. Multicast Revisited. Motivation: multiple hosts wish to receive the same data from one or more senders

chul
Download Presentation

Multicast

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Multicast Outline Multicast revisited Protocol Independent Multicast - SM Future Directions

  2. Multicast Revisited • Motivation: multiple hosts wish to receive the same data from one or more senders • Multicast routing defines extensions to IP routers to support broadcasting data in IP networks • Until now IP has only facilitated a point to point routing • Multicast data is sent and received at a multicast address which defines a group • Simple notion of a group is a TV channel • Data is sent and received in multicast groups via routing trees from sender(s) to receivers. • Protocols are principally concerned with setting up and maintaining trees • Note: All multicast messaging is sent via unicast CS 640

  3. Protocol types • Dense mode protocols • assumes dense group membership • Source distribution tree and NACK type • DVMRP (Distance Vector Multicast Routing Protocol) • PIM-DM (Protocol Independent Multicast, Dense Mode) • Example: Company-wide announcement • Sparse mode protocol • assumes sparse group membership • Shared distribution tree and ACK type • PIM-SM (Protocol Independent Multicast, Sparse Mode) • Examples: a Shuttle Launch CS 640

  4. PIM-SM overview (1) • Developed due to scaling issues • Flooding is generally a real bad idea • Based on creating routing tree for a group with Rendezvous Point (RP) as a root for the tree • RP is a focus for both senders and receivers • Explicit join model • Receivers send Join towards the RP • Sender send Register towards the RP • Supports both shared trees (default) and source trees • RPF check depends on tree type • For shared tree (between RP and receivers), uses RP address • For source tree (between RP and source), uses Source address CS 640

  5. PIM-SM overview(2) • Only one RP is chosen for a particular group • RP statically configured or dynamically learned (Auto-RP, PIM v2 candidate RP advertisements) • Data forwarded based on the source state (S, G) if it exists, otherwise use the shared state (*, G) • (*,G) means all senders • RFC2362 –“PIM Sparse Mode Protocol Spec” (experimental) • Internet Draft: draft-ietf-pim-v2-sm-00.txt (October 1999) CS 640

  6. PIM-SM Basics • PIM Neighbor Discovery • PIM SM Forwarding • PIM SM Joining • PIM SM Registering • PIM SM SPT-Swichover • PIM SM Pruning • PIM SM Bootstrap • PIM SM State Maintenance CS 640

  7. PIM SM Tree Maintenance • Periodic Join/Prunes are sent to all PIM neighbors • Periodic Joins refresh interfaces in a PIM neighbor’s downstream list • Periodic Prunes refresh pruned state of a PIM neighbor • There is a designated router (DR) for each local network and all other routers get pruned • Received multicast packets reset (S,G) entry expiration timers. • (S,G) entries are deleted if timers expire CS 640

  8. PIM-SM(1) S Source A B RP D C E R2 R1 Receiver 1 Receiver 2 CS 640

  9. PIM-SM(2) S Receiver 1 Joins Group GC Creates (*, G) State, Sends(*, G) Join to the RP Source A B RP D Join C E R2 R1 Receiver 1 Receiver 2 CS 640

  10. PIM-SM(3) S RP Creates (*, G) State Source A B RP D C E R2 R1 Receiver 1 Receiver 2 CS 640

  11. PIM-SM(4) S Source Sends DataA Sends Registration to the RP Source IP tunnel between A and RP since multicast tree is not established Register Data A B RP D C E R2 R1 Receiver 1 Receiver 2 CS 640

  12. PIM-SM(5) S RP decapsulates RegistrationForwards Data Down the Shared TreeSends Joins Towards the Source Source join join A B RP D C E R2 R1 Receiver 1 Receiver 2 CS 640

  13. PIM-SM(6) S RP Sends Register-Stop OnceData Arrives Natively Source Register-Stop A B RP D C E R2 R1 Receiver 1 Receiver 2 CS 640

  14. PIM-SM(7)SPTSwitchover S C Sends (S, G) Joins to Join theShortest Path Tree (SPT) Source A B RP D join C E R2 R1 Receiver 1 Receiver 2 CS 640

  15. PIM-SM(8) S C starts receiving Data natively Source A B RP D C E R2 R1 Receiver 1 Receiver 2 CS 640

  16. PIM-SM(9) S C Sends Prunes Up the RP tree forthe Source. RP Deletes (S, G) OIF andSends Prune Towards the Source Source Prune Prune A B RP D Prune C E R2 R1 Receiver 1 Receiver 2 CS 640

  17. PIM-SM(10) S B, RP pruned Source A B RP D C E R2 R1 Receiver 1 Receiver 2 CS 640

  18. PIM-SM(11) S New receiver2 joinsE Creates State and Sends (*, G) Join Source A B RP D C E join R2 R1 Receiver 1 Receiver 2 CS 640

  19. PIM-SM(12) S C Adds Link Towards E to the OIFList of Both (*, G) and (S, G)Data from Source Arrives at E Source A B RP D C E R2 R1 Receiver 1 Receiver 2 CS 640

  20. Inter-Domain Multicast Routing • BGP4+ (Multicast BGP) for short-term solution • Tweeks to BGP4 to support multicast • Multicast Address Set and Claim (MASC) • Hierarchical multicast address allocation at domain level • Dynamic allocation (not permanent) of addresses by “set and claim with collision” • Border Gateway Multicast Protocol (BGMP) • Use a PIM-like protocol between domains (“BGP for multicast”) CS 640

  21. MASC • Assume Addr(A) is allocated to domain A and domains B and C sit “below” A in a domain hierarchy • B selects Addr(B) which is subset of Addr(A) and send claim (addr(B)) message to A and C • A forwards claim to all children except B. • If any of A’s children is already using Addr(B) they will report a collision to A. • A will notify B of the collision and B will select other address space. • Address space information is used to create distribution tree using BGMP. • Stored in M-RIB (Multicast Routing Information Base) CS 640

  22. BGMP • BGMP builds shared tree of domains for a group • Uses a rendezvous mechanism at the domain level • Shared tree is bidirectional • Root of shared tree of domains is at root domain • Runs in routers that border a multicast routing domain • Runs over TCP • Joins and prunes travel across domains • Can build unidirectional source trees • M-IGP (multicast Intra-Gateway Protocol) tells the borders about group membership CS 640

  23. Multicast Routers • mrouted (Xerox PARC) : DVMRP • GateD (Merit) : DVMRP, PIM-DM, PIM-SM • Cisco IOS : DVMRP, PIM-DM, PIM-SM CS 640

  24. M-Bone • Wide area IP multicast test bed using IP-in-IP tunneling • Routing protocol • DVMRP is used • Transition to PIM (DM, SM) is ongoing • Started in March 1992 for audio broadcasting of IETF meeting (San Diego) • Latest tolopology • ftp://ftp.parcftp.xerox.com/pub/net-research/mbone/maps/mbone-map-big.ps • About 6000 (S,G) entries • Discussion list: mbone@isi.edu CS 640

  25. Session Directory CS 640

  26. Example Session CS 640

  27. M-BONE in 1994 CS 640

  28. M-BONE in 1996 CS 640

  29. M-BONE in 1998 CS 640

  30. Future Mulicast Service • Current multicast service - latency and packet drop • Research for “Reliable multicast” is actively going on for; • large scale interactive gaming on the Internet • Distributed databases • large scale news distribution etc. CS 640

  31. Reliable multicast technology • SRM ( Scalable Reliable Multicast) • multicast with re-transmit (with random back-off) • All nodes can re-transmit datagram (Multicast/Unicast) • MTP (Multicast Transport Protocol: RFC1301) • FEC (Forward Error Correction) • error packet recovery by redundant packets CS 640

More Related