17: IP MulticastOutlineWhat is multicast?UnicastMulticastIP Multicast IntroductionIP MulticastInternet Group Management Protocol (IGMP)IGMP Example (1)IGMP Example (2)Source Specific Filtering: IGMPv3Multicast Routing DiscussionData FloodingReverse Path Forwarding (RPF)Reverse Path Forwarding ExampleData Distribution ChoicesSource Rooted vs Shared TreesDistance Vector Multicast Routing (DVMRP)DVMRP AlgorithmTruncated Reverse Path Multicast ExampleDVMRP Pruning ExampleDVMRP Grafting ExampleDVMRP ProblemsCore Based Trees (CBT)Group Management in CBTSending Data in CBT (1)Sending Data in CBT (2)Protocol Independent Multicast (PIM)PIM Sparse ModeGroup Management in PIM-SMSending Data in PIM-SMPIM-SM Source Specific BypassRP Joins Source Specific TreeProblems with PIMClassification of Tree Building ChoicesBorder Gateway Multicast Protocol (BGMP)IP Multicast in the Real WorldCommercial MotivationISP ConcernsEconomics of MulticastMulticast ProblemsCurrent ISP Multicast SolutionMulticast TunnelingMulticast Tunneling Example (1)Multicast Tunneling Example (2)MBoneMBone UsageFuture?OuttakesSlide 50Slide 51IGMPv3 Source Filtering (1)IGMPv3 Source Filtering (2)Scoping Multicast TrafficTTL Scoping ExampleAdministrative Scoping ExampleReliable MulticastPIM Rendezvous Point (RP)PowerPoint PresentationSlide 60Administrative Control of TrafficChoosing a Shared Tree RootMulticast Address AllocationMulticast Address Allocation ArchitectureMulticast Address Allocation ExampleAddress Allocation Message ExchangeOperational ProblemsBackchannel TunnelingDebugging Multicast Problems4: Network Layer 4a-117: IP MulticastLast Modified: 01/14/19 12:02 AMBased on slides by Gordon ChaffeeBerkeley Multimedia Research CenterURL: http://bmrc.berkeley.edu/people/chaffee4: Network Layer 4a-2OutlineIP MulticastMulticast routingDesign choicesDistance Vector Multicast Routing Protocol (DVMRP)Core Based Trees (CBT)Protocol Independent Multicast (PIM)Border Gateway Multicast Protocol (BGMP)Issues in IP Multicast Deplyment4: Network Layer 4a-3What is multicast?1 to N communicationNandwidth-conserving technology that reduces traffic by simultaneously delivering a single stream of information to multiple recipients Examples of MulticastNetwork hardware efficiently supports multicast transport•Example: Ethernet allows one packet to be received by many hostsMany different protocols and service models •Examples: IETF IP Multicast, ATM Multipoint4: Network Layer 4a-4UnicastRSenderProblemSending same data to many receivers via unicast is inefficientExamplePopular WWW sites become serious bottlenecks4: Network Layer 4a-5MulticastRSenderEfficient one to many data distribution4: Network Layer 4a-6IP Multicast IntroductionEfficient one to many data distributionTree style data distributionPackets traverse network links only onceLocation independent addressingIP address per multicast groupReceiver oriented service modelApplications can join and leave multicast groupsSenders do not know who is listeningSimilar to television modelContrasts with telephone network, ATM4: Network Layer 4a-7IP MulticastServiceAll senders send at the same time to the same groupReceivers subscribe to any groupRouters find receiversUnreliable deliveryReserved IP addresses224.0.0.0 to 239.255.255.255 reserved for multicastStatic addresses for popular services (e.g. Session Announcement Protocol)4: Network Layer 4a-8Internet Group Management Protocol (IGMP)Protocol for managing group membershipIP hosts report multicast group memberships to neighboring routersMessages in IGMPv2 (RFC 2236)•Membership Query (from routers)•Membership Report (from hosts)•Leave Group (from hosts)Announce-Listen protocol with SuppressionHosts respond only if no other hosts has respondedSoft State protocol4: Network Layer 4a-9IGMP Example (1)Network 1Host 1 begins sending packetsNo IGMP messages sentPackets remain on Network 1Router periodically sends IGMP Membership QueryNetwork 2Router12434: Network Layer 4a-10IGMP Example (2)Network 1Host 3 joins conferenceSends IGMP Membership Report messageRouter begins forwarding packets onto Network 2Host 3 leaves conferenceSends IGMP Leave Group messageOnly sent if it was the last host to send an IGMP Membership Report messageNetwork 2Router12433Membership Report33Leave Group4: Network Layer 4a-11Source Specific Filtering: IGMPv3Adds Source Filtering to group selectionReceive packets only from specific source addressesReceive packets from all but specific source addressesBenefitsHelps prevent denial of service attacksBetter use of bandwidthStatus: Internet Draft?4: Network Layer 4a-12Multicast Routing DiscussionWhat is the problem?Need to find all receivers in a multicast groupNeed to create spanning tree of receiversDesign goalsMinimize unwanted trafficMinimize router stateScalabilityReliability4: Network Layer 4a-13Data FloodingSend data to all nodes in networkProblemNeed to prevent cyclesNeed to send only once to all nodes in networkCould keep track of every packet and check if it had previously visited node, but means too much stateSenderR3R1R24: Network Layer 4a-14Reverse Path Forwarding (RPF)Simple technique for building treesSend out all interfaces except the one with the shortest path to the senderIn unicast routing, routers send to the destination via the shortest pathIn multicast routing, routers send away from the shortest path to the sender4: Network Layer 4a-15Reverse Path Forwarding ExampleR5 R6R3R2R1R4 R7Sender2. Router R2 accepts packets sent from Router R1 because that is the shortest path to the Sender. The packet gets sent out all interfaces.1. Router R1 checks: Did the data packet arrive on the interface with the shortest path to the Sender? Yes, so it accepts the packet, duplicates it, and forwards the packet out all other interfaces except the interface that is the shortest path to the sender (i.e the interface the packet arrived on). DropDrop3. Router R2 drops packets that arrive from Router R3 because that is not the shortest path to the sender. Avoids cycles.4: Network Layer 4a-16Data Distribution ChoicesSource rooted treesState in routers for each senderForms shortest path tree from each sender to receiversMinimal delays from sources to destinationsShared treesAll
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