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Chia-Hui Huang Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 1 Multicast Concepts IP Multicast Application Layer Multicast Simulation tools Summary Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 2 What is multicast ? Multicast applications Why multicast ? Terminologies Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 3 Multicast communications refers to one-to-many or many-to-many communications. 140.124.180.0/24 140.124.181.0/24 Sender Receiver 140.124.182.0/24 140.124.183.0/24 140.124.180.0/24 140.124.181.0/24 Sender Receiver Receivers Receiver 140.124.182.0/24 140.124.183.0/24 Unicast forwarding Receiver Receivers Multicast forwarding Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 4 Multicast Applications One-to-many Scheduled audio/video distribution End System Multicast File Distribution … Many-to-many Multimedia Conferencing Concurrent Processing Multi-player Games P2P file sharing … Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 5 Bandwidth Consumption Server Load Multicast vs. Unicast User Latency Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 6 IP Multicast Application Layer Multicast Multicast Techniques Overlay Multicast Network Type Overlay Network Topology Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 7 IP Multicast fundamentals Multicast Group IP Multicast Routing Protocols IP Multicast Requirements (Constrains/Drawback) Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 8 Components of the IP Multicast service IP Multicast Addressing IP Group Management Multicast Routing One to many communication over an IP infrastructure Multicast groups are identified by IP addresses in the range 224.0.0.0 – 239.255.255.255 (class D address) The IP Multicast service is unreliable UDP Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 9 IP multicast Group Receivers must Join multicast group (IGMP) Sender send to group address Multicast router find delivery paths and replicate the packet Receiver Receiver Group Member 2 Group Member 1 Sender & Receiver Group Member 1 Sender Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 Receiver Group Member 1 Group Member 2 10 Graph problem Build a spanning tree between all members of a multicast group Solutions Shortest Path Tree (Source-Based Tree) Minimum-Cost Tree ( shared tree ) Steiner tree problem Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 11 Multicast routing in practice Source-Based Tree Build a tree that minimizes the path cost from the source to each receiver – shortest path tree Builds one shortest path tree for each sender Tree is build from receiver to the sender – Reverse Path Forwarding Shared Tree Build a single distribution tree that is shared by all senders Select one router as a “core” (rendezvous point) All receivers build a shortest path to the core Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 12 Multicast forwarding techniques (RFC1075) Reverse Path Forwarding (RPF) Avoid duplicate packets ( look-free forwarding ) RPF check When a multicast packet is received, note its source ( S ) and interface ( I ) If I belongs to the shortest path from S, forward to all interfaces except I If test in step 2 is false, drop the packet Packet is never forwarded back out the RPF interface Reverse Path Multicasting ( RPM ) Take into account Multicast Group Membership Flood-and-Prune (cascade of prune messages) Both the group membership and Internet topology can change dynamically … Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 13 Prune Message Removes a link from the multicast tree Who sends prune message ? 1. A router with no group members in its local network and no connection to other routers ( sent on RPF interface ) 2. A router with no group members in its local network which has received a prune message on all non-RPF interfaces ( sent on RPF interface ) 3. A router with group members which has received a packet from a non-RPF neighbor ( to non-RPF neighbor ) Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 14 Multicasting Protocols Source-Based Tree DVMRP Share Tree MOSPF CBT PIM PIM-DM PIM-SM Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 15 DVMRP Distance Vector Multicast Routing Protocol Each router maintains a multicast routing table by exchanging distance vector information among routers Flood multicast packets based on RPF rule (flood-and-prune) Pruning / Grafting strategies Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 16 CBT Core-Based Tree Core placement Manual Bootstrap Tree formation JOIN_REQUEST Transit states (router) JOIN_ACK Confirmed states (router) Data forwarding Source to core router – unicast (group-id is placed in the option field of packet) Multicast packets span the tree based on the packet’s group-id Tree maintenance ECHO_REQUEST, ECHO_REPLY Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 17 Support for IP Multicast ( multicast functions ) Multicast Routing protocol Router Replicate & Forward Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 18 Multicast Service Requirements Congestion Control Flow Control Group State Multicast Service Requirements Security Consequence … Disabled by router Reliability Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 19 Implement Multicast Service at the End System ??? No infrastructure (router) support is needed Overlay Multicast !! ??? Alternate technique for multicasting ???Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT Application Layer Multicast !! 2017/5/25 20 Application Layer Multicast (ALM) concepts Routing Protocols Issues ( research topics ) Mechanism Theoretical Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 21 Application Layer Multicast (ALM) Implement multicast functionality at the application layer Application layer multicast data packets are replicated at end-hosts End-hosts form an overlay network No underlying topology information Metrics – performance penalty Link stress Number of duplicate copies of a packet over a physical link Max stress Total stress Relative Delay Penalty ( RDP ) Relative delay increase between two nodes against unicast delay between the same two nodes Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 22 ALM routing protocols organize the group into Control topology ( P2P overlay network ) Data topology ALM Routing Protocols Mesh-first ESM (Narada) Tree-first Yoid Implicitly HMTP NICE CAN Scribe Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 23 Mesh-first - ESM Control topology Mesh structure Data topology tree structure created using RPF, e.g. DVMRP Tree-first - HMTP Control topology tree structure Construct a shared data delivery tree directly Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 24 Implicitly - NICE Control topology According to some specific properties ( e.g. distance ) Mesh / Tree structure Data topology Deliver data according to some ”forwarding rules” AL Multicast is an application of P2P network Group management mechanism of P2P network form control topology of AL Multicast E.g. CAN – CAN P2P network Scribe – pastry P2P network Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 25 Group management ( P2P Network ) Static Dynamic Maintenance ( Join, Leave and failure) Routing protocol Number of sources Single source Multiple sources Service specific Reliable, trust, delay, bandwidth consumption … etc Congestion & flow control Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 26 Performance Metrics Link stress RDP Number of hops and delays between parent and child hosts in an overlay tree Degree of hosts Bottleneck … Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 27 Cost of ALM Overlay cost – number of underlying hops traversed by every overlay link Lo (h, k , n) denotes overlay cost for an overlay o when n is the number of hosts Underlying tree model – k-ary tree Normalized Overlay Cost Overlay cost vs. average number of hops for unicast Lo (h, k , n) Ro (h, k , n) U o (h, k ) Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 28 Characteristic of normalized overlay cost Ro (h, k , n) n x Chuang and Sirbu (1998) found that the ratio between the total number of multicast links and the average unicast path length exhibits a Power-law. Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 29 Optimal solution ( normalized overlay cost ) IP Multicast LIPMulticast (n) n 0.8 U o (h, k ) ALM – Sonia Fahmy and Minseok Kwon (2003) Receivers at leaf nodes Lo (h, k , n) Ro (h, k , n) n 0.92 U o (h, k ) Receivers at leaf or non-leaf nodes Lo (h, k , n) Ro (h, k , n) n 0.83 U o (h, k ) Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 30 General simulator OMNet++ OverSim Framework – P2P simulation framework INET Framework – implement protocol stack of wire and wireless network NS-2 Peer-to-Peer network simulator P2PSim OverlayWeaver PlanetSim Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 31 IP Multicast But ... Multicast So ... Disabled by Efficiency Service router Requirements Alternative ... Application Layer Multicast Design Network Issues infrastructure But ... remain unchanged Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT Design Trade-off 2017/5/25 32 Issues & Trade-off Group Management Mesh vs. Tree Congestion & Flow Control Routing Protocol Source Tree vs. Shared Tree Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 33 1. D. Waitzman, C. Partridge and S. Deering, “Distance Vector Multicast Routing Protocol,” RFC 1075, IETF Network Working Group, November 1988. 2. A. Ballardie, “Core Based Trees (CBT) Multicast Routing Architecture,” RFC 2201, IETF Network Working Group, September 1997. 3. B. Quinn and K. Almeroth, “IP Multicast Applications: Challenges and Solutions,” RFC 3170, IETF Network Working Group, September 2001 4 S. Banerjee and B. Bhattacharjee, “A Comparative study of application layer multicast protocols,” Unpublished report, Department of Computer Science, University of Maryland, available at Wireless and Broadband Network Laboratory 2017/5/25 34 http://pages.cs.wisc.edu/~suman/pubs.html (WBNLAB) Dept. of CSIE, NTUT 5. J. Chuang and M. Sirbu, “Pricing multicast communications: A cost based approach,” in Proc. Internet Society INET, Jul. 1998. 6. Sonia Fahmy and Minseok Kwon, “Characterizing Overlay Multicast Networks and Their Costs,” IEEE Transaction on Networking, Vol. 15, no. 2, April 2007 Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 35 Appendix Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 36 source H1 (a) Set routing tables according to RPF R1 R2 R5 source H1 R1 R2 R3 H2 R4 R6 R8 H3 Joined source R7 R3 H2 H4 Joined R1 H5 R6 ne Pru R4 Prune H3 R7 Pru ne Pru ne R7 Pru Pru (b) Flood Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT ne R6 ne H5 H4 Joined ne Prune R8 H2 e Prune Prune n Pru Prune H3 Joined R4 R3 R2 Pru R5 H1 R8 H5 2017/5/25 H4 Joined (c) Prune 37 source H1 source R1 R4 H3 Joined H2 R7 H4 Joined R2 R3 Core Router H2 R4 R6 Join R5 Join J oin Join Core Router R1 R3 Join R2 H1 R8 R6 R5 H3 Joined R7 H5 Joined (a) Receiver sends a Join message to RPF neighbor with respect to core router H4 Joined R8 H5 Joined (b) Data forwarding Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 38 A network built on top of one or more existing networks Overlay link Receivers Source Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 39 Host Router 1 1 3 A A B 4 2 1 1 A 1 25 2 1 27 Application Layer Multicast 3 Unicast 1 1 4 1 25 2 1 3 27 3 B 1 4 3 29 2 4 2 1 A 27 2 4 B 1 B 2 Network Layer Multicast 1 3 2 4 Wireless and Broadband Network Laboratory Application Layer Multicast 2017/5/25 (WBNLAB) Dept. of CSIE, NTUT <1,2> and <1,3> = 1 29 <1,4> = 27 1 The penalty of Application Multicast !! 40 Given: A Weighted graph G (V , E ) and a vertices subset S V Find: A tree of minimal weight which spanning S NP-Complete problem Approximation ApproxmiationRatio achieved cos t optimal cos t Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 41 Steiner tree vs. minimum spanning tree 2 Steiner point 2 1 2 1 1 2 1 1 1 2 2 (a) Network graph 1 Steiner point 1 1 2 2 2 2 2 1 1 1 Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT (b) Steiner Tree 2 2017/5/25 (c) Minimal Spanning Tree 42 ESM Narada Narada Components Mesh management Ensure mesh remains connected in face of membership changes Random join Mesh optimization Members periodically probe other members at random and Add new link/ Drop existing link Spanning tree construction Source rooted shortest delay spanning trees of mesh Constructed using well known routing algorithms Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 43 Host Multicast Rendezvous Point ( HMRP ) Maintain the root address of current tree Cluster nearby members together Round-Trip Time ( RTT ) as measurement metric Every member must maintain information … List of children – for join procedure Root path – for leave, improvement and partition recovery Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT 2017/5/25 44 B A Join Request A C D B E F C D E F N N New Member New Member (a) (c) A B Join Request A C D E F Query Nearest B C N New Member D E F N (b) Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT Join Request (d) 2017/5/25 New Member 45 NICE Hierarchy Hierarchical arrangement of members Topological clusters Layer 2 Layer 1 G C B Layer 0 G C E G K H K A D F Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT I 2017/5/25 J 46 A – layer 0 A7 B – layer 1 B1 C – layer 2 C0 Rendezvous Point RP B0 A0 A7 Create control topology according to “distance” A1 B2 A2 A7 RP A7 RP RP Join B1 B1 B1 Join C0 Join Join New New New C0 C0 A1 B0, B1, B2 C0 A1 A1 Join Attach B0 A0 A2 B2 B0 A0 A2 B2 Wireless and Broadband Network Laboratory (WBNLAB) Dept. of CSIE, NTUT B0 A0 2017/5/25 A2 B2 47 Data delivery path A0 as source A7 as source Forwarding rules : Source : Forward to cluster members and cluster leader Cluster Leader : cluster members C0 as source A7 B1 B1 C0 C0 A1 B1 C0 A1 A1 B0 A0 A7 A7 B2 A2 (a) A0 is the source B0 A0 B2 A2 (b) Network A7 is the Laboratory source Wireless and Broadband (WBNLAB) Dept. of CSIE, NTUT B0 A0 2017/5/25 B2 A2 (c) C0 is the source 48