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Design an Application Layer Multicast

Design an Application Layer Multicast. CHUN-TING, WU Teacher: KAI-WEI, KE. Outline. Introduction MANET Examples Performance Matrics Conclusions. Overview. Traditional network architectures distinguish between two types of entities

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Design an Application Layer Multicast

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  1. Design an Application Layer Multicast CHUN-TING, WU Teacher: KAI-WEI, KE

  2. Outline • Introduction • MANET • Examples • Performance Matrics • Conclusions

  3. Overview • Traditional network architectures distinguish between two types of entities • end systems (hosts) and the network (routers and switches). • The key architectural question is: what new features should be added to the IP layer? • Multicast and QoS

  4. What is a multicast • Delivery of information to a group • Creating copies only when the links to the multiple destinations

  5. Why multicasting • video-on-demand • live media streaming • video conferencing • multiplayer games • Real time and large data flow

  6. IP layer vs. Application layer • In deciding whether to implement multicast services at the IP layer or at end systems, there are two conflicting considerations that we need to reconcile.

  7. IP layer vs. Application layer • First, IP Multicast requires routers to maintain per group state • violate the “stateless” architectural principle, and introduce high complexity and serious scaling. • Second, IP Multicast calls for changes at the infrastructural level • slows down the pace of deployment.

  8. Finally, IP Multicast is providing higher level features such as reliability, congestion control, flow control, and security has been shown to be more difficult than in the unicast case.

  9. We consider a model in which multicast related features, such as group membership, multicast routing and packet duplication, are implemented at end systems, assuming only unicast IP service.

  10. To be resolved • An overlay approach to multicast, however efficient, cannot perform as well as IP Multicast. • It is impossible to completely prevent some redundant traffic on physical links. • Communication between end systems involves increasing latency.

  11. (b) naive unicast transmission. • (c) the IP Multicast tree constructed by DVMRP • (d) an “intelligent” overlay tree

  12. Conceptual comparison

  13. ALM properties • GROUP MANAGEMENT • Mesh First vs. Tree First • Source Specific Tree vs. Shared Tree • Refinement • ROUTING MECHANISM • Shortest Path • Minimum Spanning Tree • Clustering Structure

  14. Mesh First vs. Tree First • Tree-based • Source node as the root, thus there is only one single path between every pair of sender and receiver. • It’s very efficient since the routing information needs to be maintained is very little. • Mesh-based • More than one path between each sender and receiver pair exists. • More robust but less efficient.

  15. Source Specific Tree vs. Shared Tree • Source-tree-based • It construct a multicast tree among all the member nodes for each source node.(usually this is a shortest path tree) • More efficient. • Too much routing information to maintain. • Shared-tree-based • It constructs only one multicast tree for a multicast group including several source nodes. (usually this is a minimum spanning tree) • Every source uses this tree to do multicast. • Less efficient. • It reduces the overhead greatly by maintaining less routing information.

  16. Refinement • Constructed trees might be different • Depending upon the order of joining requests • Construct the tree in real time and have no a-priori knowledge of node arrivals • Local optimum to the global optimum and improves the system’s performance

  17. Shortest Path • A Shortest Path Tree constructs a minimum cost path from a source node to all its receivers • A source-specific multicast tree or in graph theoretic terms a rooted tree

  18. Minimum Spanning Tree • Construct a low cost tree • Used by a shared tree

  19. Clustering Structure • Construct a hierarchical cluster of nodes with each cluster having a head • Advantages • Reduction in control overhead • Faster joining and leaving • A sub-optimal tree

  20. MANET • Form a temporary and dynamic wireless network on a wireless channel without the fixed infrastructure • Self-organizing collection of Mobile Nodes • Low bandwidth, mobility and low power • Due to the limited transmission range, multiple hops may be needed

  21. IP network and MANET • router vs. forwarding node • traverse internet vs. multi-hops routing • fixed vs. topology changes frequently

  22. Flooding-based • Proactive (table-driven) • continuously evaluate routes • maintain up-to-date routing information • periodically flood its location to other nodes • maintains a location table • Reactive (on-demand) • routing creates routing only when desired • in searching of the destination

  23. Quorum-based • Explicit • Location update is sent to a defined subset (update quorum) • Location query is sent to a subset (query quorum) • Implicit • Location servers are chosen via a hashing function

  24. MAODV • Multicast On-demand Distance Vector routing protocol • This protocol uses broadcast to find the route in an on-demand way and constructs a shared routing tree.

  25. Group member Multicast Tree member Ordinary node Potential Group member Multicast link Communication link MAODV Example Group Join Process Broadcast - RREQ Multicast Activation Broadcast Group Hello Only GM Responds L

  26. Group member Multicast Tree member Ordinary node Potential Group member Multicast link Communication link MAODV Example Leaving a Multicast Group Non leaf Node Must remain as a Tree member L Leaf Node Can remove itself from MT Again Leaf Node Remove himself from MT

  27. Local Connectivity Management • Node must periodically hear from active neighbors to know they are still within range • Every time hear broadcast, update lifetime • If no broadcast with hello_interval, broadcast Hello packet • Failure to hear from a neighbor for • (1 + allowed_hello_loss ) * hello_lifetime indicates loss of link

  28. Unicast Route Discovery • Source broadcasts • Route Request(RREQ) • <J_flag, R_flag, Bcast_ID, Src_Addr, Src_Seq#, Dst_Addr, Dst_Seq#, HopCnt> • Node can reply to RREQ if • – It is the destination • – It has a “fresh enough” route to the destination • Nodes create reverse route entry • Record Src IP Addr / Broadcast ID to prevent multiple processing RREQ Source Destination

  29. Unicast Route Discovery • Source broadcasts • Route Request(RREQ) • Node can reply to RREQ if • – It is the destination • – It has a “fresh enough” route to the destination • Nodes create reverse route entry • Record Src IP Addr / Broadcast ID to prevent multiple processing Source RREP Destination

  30. Unicast Route Discovery • Source broadcasts • Route Request(RREQ) • Node can reply to RREQ if • – It is the destination • – It has a “fresh enough” route to the destination • Nodes create reverse route entry • Record Src IP Addr / Broadcast ID to prevent multiple processing Source Destination

  31. Forward Path Setup • Nodes along path create forward route to dest • Source begins sending data when receives first RREP Source Data Destination

  32. Design properties • GROUP MANAGEMENT • Tree First • Shared Tree • No refinement • ROUTING MECHANISM • Minimum Spanning Tree • MANET ROUTING • Reactive • Flat

  33. Performance Matrics • Latency • end-to-end delay • Bandwidth • throughput at the receiver • Stress • number of identical copies of a packet carried by a physical link

  34. Performance Matrics • Resource Usage • 57 / 30 / 32 • Protocol Overhead • total bytes of non-data traffic

  35. Conclusions • Although, MANET multicast is an ALM, using wired mech. cannot perform well. • Actually, there is no a “one-for-all” scheme that works well with different scenarios. • Highly dynamic environment, nodes move arbitrarily, thus network topology changes frequently and unpredictably • Moreover, bandwidth and battery power are limited. • Make multicast extremely challenging

  36. References • Tu, W. & Jia, W., “An End Host Multicast Protocol for Peer-to-Peer Networks,” LCN '05: Proceedings of the The IEEE Conference on Local Computer Networks 30th Anniversary IEEE Computer Society, 2005, pp. 392-399 • Hosseini, M., Ahmed, D., Shirmohammadi, S. & Georganas, N., “A Survey of Application-Layer Multicast Protocols,” Communications Surveys & Tutorials, IEEE, 2007, Vol. 9(3), pp. 58-74 • Junhai, L., Danxia, Y., Liu, X. & Mingyu, F., “A survey of multicast routing protocols for mobile Ad-Hoc networks,” Communications Surveys Tutorials, IEEE, 2009, Vol. 11(1), pp. 78 -91 • Perkins, C. & Royer, E., “Ad-hoc on-demand distance vector routing,” Mobile Computing Systems and Applications, 1999. Proceedings. WMCSA '99. Second IEEE Workshop on, 1999, pp. 90 -100

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