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draft-ietf-mboned-iesg-gap-analysis-00.txt

Analysis of IP multicast service models, protocols, and deployments, focusing on gaps and recommendations for improvement. Issues with existing implementations and proposal for long-term framework.

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draft-ietf-mboned-iesg-gap-analysis-00.txt

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  1. draft-ietf-mboned-iesg-gap-analysis-00.txt Internet Multicast Gap Analysis From the MBONED Working Group For the IESG

  2. Overview and Background • IETF-54: MBONED working group recommends that MSDP publish current work as Informational, and shut down. • Short term: Document existing MSDP implementations and deployments • Long term: Perform “gap analysis” of IP multicast service model, protocols, and deployment

  3. RFC 1112 • Ethernet Multicast for IPv4 Applications • Host Extensions • IPv4 group address range • Static mapping of IPv4 group addresses to Ethernet MAC addresses • Receiver interest notification (IGMP) • Collision-sense multiple-access (CSMA) for multicast IPv4 senders. Transmit at will.

  4. RFC 1112 • Gateways “may exist” for moving IPv4 datagrams between Ethernets • Later known as Any Source Multicast (ASM)

  5. Dense Mode IP Multicast Routing • Extend CSMA model to the Internet • Transmit At Will • Traffic-driven forwarding and pruning • Does not scale • Meta-stable failure mode • Downstream gateways can’t prune successfully • Routing and forwarding mixed

  6. (Reachability) Protocol Independent Multicast Routing • Separate forwarding and routing • Unicast reachability: • Where to forward towards destination • Multicast reachability: • Where to request from source • Examples: RIP, OSPF, BGP, etc.

  7. Sparse Mode Multicast Routing • Forward datagrams when requested by downstream • ASM bootstrap: • Dense-mode control plane • Maintains CSMA model from RFC 1112

  8. Source Specific Multicast • Receivers identify both source and group • Explicit request from traffic • Fall-out from Sparse Mode Routing • User creates source-rooted forwarding trees • No need for ASM control plane

  9. Bursty Source Problem • Assumed CSMA model: Transmit At Will. • Strictly limited control and announcement traffic • Intended to salvage dense-mode routing from collapse • In sparse-mode context, causes forwarding state flaps • Requires control plane to stay dense • Requires control plane to forward packets

  10. Co-mingled IP and Ethernet Routing • IEEE 802 bridges must become IPv4 aware in order to constrain flooding of IPv4 multicast to all ports. • IEEE GARP/GMRP protocol suite for IP multicast on IEEE 802 networks?

  11. Inter-Domain IP Multicast Exchanges • Unicast IP datagrams can traverse an exchange point more than once, if necessary. • Multicast IP datagrams cannot traverse an exchange point more than once. Why?

  12. Overloaded mapping of IP Addresses to IEEE MAC Addresses • RFC 1112 IPv4 to IEEE 802 MAC address: 32:1 • RFC 2464 (Section 7): 2^96:1(that’s 79,228,162,514,264,337,593,543,950,336:1) • Even IEEE 802 bridges that understand IPv4 IGMP and/or IPv6 MLD still cannot filter unwanted traffic.

  13. Recommendations to IESG (1/3) • Direct MAGMA Working Group to develop a successor to IGMP/MLD • Media agnostic (not Ethernet-driven) • Dynamic mapping of IP group addresses to link-layer point-to-multipoint addresses • Support (*,G), (S,G), and (S,G,upstream) modes • Registration of sources prior to transmission • Implement first at inter-domain exchange points • Not Applicable for IPv4 TTL=1 or IPv6 scopes 0, 1, and 2

  14. Recommendations to IESG (2/3) • Encourage development of protocol to spread knowledge of active sources to interested gateways • Do not actually forward multicast datagrams • Distributed database function • Discourage work on IGMP or MLD snooping • Encourage use of GARP/GMRP on IEEE 802 networks

  15. Recommendations to IESG (3/3) • Minimum source transmit frequency • Maintain Sparse Mode forwarding state • Eliminate requirement for control plane to carry data

  16. Questions?

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