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Scalable Fair Reliable Multicast Using Active Services

Scalable Fair Reliable Multicast Using Active Services. Sneha Kumar Kasera, Bell Labs Supratik Bhattacharyya, UMass Mark Keaton, TASC Diane Kiwior, TASC Jim Kurose, UMass Don Towsley, UMass Steve Zabele, TASC. Why Reliable Multicast ?. sender. applications one-to-many file transfer

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Scalable Fair Reliable Multicast Using Active Services

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  1. Scalable Fair Reliable Multicast Using Active Services Sneha Kumar Kasera,Bell Labs Supratik Bhattacharyya, UMass Mark Keaton, TASC Diane Kiwior, TASC Jim Kurose, UMass Don Towsley, UMass Steve Zabele, TASC

  2. Why Reliable Multicast ? sender applications • one-to-many file transfer • information updates (e.g., stock quote, web cache updates) • shared whiteboard limited capacity links lossy network receivers

  3. Challenges • feedback implosion • retransmission scoping • loss recovery burden • congestion control

  4. Feedback Implosion pkt NAK ACK problem: ACK implosion solution: use NAKs • NAK implosion ? • NAK suppression (using timers) • NAK aggregation (by building hierarchy)

  5. Retransmission Scoping • retransmissions go everywhere! • how to shield receivers, links from loss recovery due to other receivers ? pkt transmission pkt lost pkt retransmission

  6. Loss Recovery Burden retransmits 1,2,3,4 • when #receivers large, each pkt lost at some rcvr with high probability • sender retransmits almost all pkts several times • how to share burden of loss recovery ? pkt 4 lost pkt 3 lost pkt 1 lost pkt 2 lost

  7. Congestion Control • heterogeneity of links, receivers • feedback implosion • fairness - how to share bandwidth with unicast, other multicast sessions ? congested link

  8. dynamic invocation of user defined computations within network preserve routing, forwarding semantics at routers for performance enhancement, not necessary for correctness Active Services sender server receivers

  9. Issues • how to place, locate, invoke, revoke services ? • what router support required ? • how to provision resources ?

  10. Feedback Aggregation Service • for avoiding feedback (ACK, NAK, loss reports etc.) implosion • exploits the physical multicast tree, no need to construct, maintain logical hierarchy • invoked at high fan-out NAK aggregation lost pkt NAK

  11. Selective Packet Discard retransmission • for retransmission scoping • retransmissions intercepted, forwarded only when requests pending • similar services for filtering undesired, low-priority packets interception no forwarding lost pkt retransmission

  12. Repair Service • servers cache pkts - allowing recovery from point of loss • efficient distribution of loss recovery burden • higher performance • caching for rate conversion [MPL 97] loss recovery

  13. Congestion Control Using Active Services (P4,T4) • feedback aggregation for tracking worst case receiver • rate conversion at servers • selectively discarding less important pkts (P1,T1) (P4,T4) (P2,T2) (P4,T4) (P1,T1) (P3,T3) congestion feedback aggregation Loss probability estimates: P1, P2, ... Round trip time estimates: T1, T2, ...

  14. Locating, Invoking, Revoking Services in AER [KBKKKTZ 99] • source path messages (SPMs) sent periodically • invoke service • establish reverse path • router support required for • interception of SPM • subcast SPM S SPM RS1 SPM RS2 • SPMs multicast but intercepted • NAKstake reverse path

  15. Network Bandwidth Reduction • bandwidth usage: total bytes transmitted over all links per correct transmission • active repair service-based (RSB) bandwidth reduction compared to • SRM: upto 60% • DR-based (DRB): upto 35% Tail : link(s) to receiver site

  16. Abone Repair Latency Measurements • experiment: sender at UWash, receiver at UMass, 3 repair servers (Lincoln Labs, Aerospace Corp, UUtah) • marked reduction in repair latency when repair services on

  17. Summary • active services comprehensively address challenges of scalable reliable multicast • future work: • other services - log service, parity encoding service, ... • composable active services • enhance signaling (SPM++)

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