multicast - Multicasting CSE 6590 Winter 2012 1 Internet...

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Unformatted text preview: Multicasting CSE 6590 Winter 2012 1 February 14, 2012 Internet Multicast Service Model Multicast group concept: use of indirection • a host “sends” IP datagrams to multicast group. • routers forward multicast datagrams to hosts that have “joined” that multicast group. 2 128.119.40.186 128.59.16.12 128.34.108.63 128.34.108.60 multicast group 226.17.30.197 Multicast Groups Class D Internet addresses reserved for multicast: Host group semantics: o anyone can “join” (receive from) multicast group. o anyone can send to multicast group. o no network-layer identification to hosts of members. Needed : infrastructure to deliver multicast-addressed datagrams to all hosts that have joined that multicast group. 3 Multicast Addressing • Class D address (see next slide) • Source: unicast IP address S Receivers: multicast group ID G, a class-D address • Each group is identified by ( S , G ) • Ethernet broadcast address (all 1’s) • 2 ways of doing IP multicast at the link layer: – Link-layer (Ethernet) broadcast – Link-layer (Ethernet) multicast Both cases need filtering at IP layer. 4 IPv4 Address Formats 5 Multicast Addressing (2) 1 . Link-layer (Ethernet) broadcast • IP multicast packet is encapsulated in an Ethernet broadcast frame and transmitted on the bus. • Every host picks up the Ethernet frame and does filtering at the IP layer to decide whether to keep or discard the frame. • Redundant reception by many hosts. 2. Link-layer (Ethernet) multicast • Requires a mapping of IP multicast address to an Ethernet multicast address (see next slide). • There are up to 32 IP class-D addresses mapped to the same Ethernet multicast address. • The IP module still has to filter out packets for non-member hosts. 6 Mapping from Class D IP adress to Ethernet multicast adress 7 Multicast Protocols Transport layer • UDP • Real-time Transport Protocol (RTP): for multimedia content • ReSerVation Protocol (RSVP): for bandwidth reservation in a multicast distribution 8 Multicast Protocols (2) Routing, delivery • On a local network (join/leave): – Internet Group Management Protocol ( IGMP ) – Multicast Listener Discovery (MLD): similar to IGMP but for IPv6 • Intra-domain (routing): – MOSPF , PIM, DVMRP • Inter-domain (routing): – Multicast Border Gateway Protocol (MBGP) 9 Joining a multicast group: 2-step process • Local : host informs local multicast router of desire to join group: IGMP (Internet Group Management Protocol) • Wide area : local router interacts with other routers to receive multicast datagram flow – many protocols (e.g., DVMRP, MOSPF, PIM) 10 IGMP IGMP IGMP wide-area multicast routing IGMP Internet Group Management Protocol (IGMP) • RFC 3376 used to exchange multicast group information between hosts & routers on a LAN...
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multicast - Multicasting CSE 6590 Winter 2012 1 Internet...

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