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Hitoshi Asaeda

80 th IETF, March 2011, Prague, Czech Republic. IGMP/MLD-Based Explicit Membership Tracking Function for Multicast Routers draft-asaeda-mboned-explicit-tracking-02. Hitoshi Asaeda. Objectives. Problem in bursty IGMP/MLD message transmission Requirement to save network resources

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Hitoshi Asaeda

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  1. 80th IETF, March 2011, Prague, Czech Republic IGMP/MLD-Based Explicit Membership Tracking Function for Multicast Routersdraft-asaeda-mboned-explicit-tracking-02 Hitoshi Asaeda 80th IETF, March 2011.

  2. Objectives • Problem in bursty IGMP/MLD message transmission • Requirement to save network resources • Especially in the recent IGMPv3/MLDv2/LW-IGMPv3/LW-MLDv2 due to elimination of the report suppression mechanism • Requirement of fast leave or shortening leave latency 80th IETF, March 2011.

  3. Functions • The explicit tracking function on routers works for: • Per-host accounting • Reducing the number of transmitted Query and Report messages • Shortening leave latencies • Maintaining multicast channel characteristics (or statistics) 80th IETF, March 2011.

  4. Objective 1: the Number of Messages Transmission • Whenever a router receives the State-Change Report, it sends the corresponding Group-Specific or Group-and-Source Specific Query messages to confirm whether the Report sender is the last member host or not. 80th IETF, March 2011.

  5. Lower Specific Query Transmission • A router enabling the explicit tracking function does not need to always ask Current-State Report message transmission to the member hosts whenever it receives the State-Change Report • Because the explicit tracking function works with the expectation whether the State-Change Report sender is the last remaining member of the channel or not 80th IETF, March 2011.

  6. Simulation • Transit Number of Members • 40 hosts individually join/leave a same channel 80th IETF, March 2011.

  7. Current-State Report – Regular Case • Responses for General Query • Responses for Group- (and-Source) Specific Query 80th IETF, March 2011.

  8. Current-State Report – With Explicit Tracking Function • Responses for General Query • No responses for Group- (and-Source) Specific Query (except for the LMQ) 0h 20m 80th IETF, March 2011.

  9. Outdated State Information • When a router expects that the State-Change Report sender was the sole member, but not the one, or when the number of receivers in the state information becomes “0”, but not “0”; • Other members remaining in the same channel will reply with identical Report messages • When a router expects that there are other members, but there isn’t, or when the number of receivers in the state information is not “0”, but it is “0”; • The router sends periodical General Query later but does not receive the corresponding Report; it then starts the leave operation • Will add some intelligence (e.g., send State-Change Report when the number of remaining members is less than “5”, etc.)? • Maybe in the future IGMP/MLD 80th IETF, March 2011.

  10. Objective 2: Leave Latency • [Last Member Query Interval] (LMQI) and [Last Listener Query Interval] (LLQI) • The maximum time allowed before sending a responding Report • [Last Member Query Count] (LMQC) and [Last Listener Query Count] (LLQC) • The number of Group-Specific Queries or Group-and-Source Specific Queries sent before the router assumes there are no local members • [Last Member Query Time] (LMQT) and [Last Listener Query Time] (LLQT) • Total time the router should wait for a report, after the Querier has sent the first query 80th IETF, March 2011.

  11. Shortening Leave Latencies • [Last Member Query Timer (LMQT)] and [Last Listener Query Timer (LLQT)] • Default: LMQI * LMQC (= 2 sec.) • Shorter value contributes to shortening leave latency • Example: • LMQC = 1, then LMQT = 1 sec. • Note, LMQI can be shorter, e.g., 0.5 sec. • Note • There is a risk that a router misses Report messages from remaining members if the router adopts small LMQC/LLQC • However the wrong expectation would be lower happened for the router enabling the explicit tracking function. 80th IETF, March 2011.

  12. Membership State Information • Membership state information • (S, G, Number of receivers, (Receiver records)) • Receiver records • (IGMP/MLD Membership/Listener Report sender's addresses) • ASM • “S” is with “Null” • EXCLUDE mode (S,G) join • Not integrate into state information? • Just keep the current state without modification • Or integrate translated ASM join into state information? 80th IETF, March 2011.

  13. Interoperability and Compatibility • Not work for old IGMP/MLD • Because of the Report suppression mechanism • Tracking router keeps the current state as is • Not work for IGMPv3/MLDv2 router changing its compatibility mode to the older version • The router keeps the current state as is 80th IETF, March 2011.

  14. Next Step • WG document? 80th IETF, March 2011.

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