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Introduction to multicast
Multicast 1 Spencer Tsai Mobile Communication & Broadband Network Lab CSIE Fu-Jen Catholic University Introduction to Multicast Multicast 2 Outline • Overview • IGMP • Multicast Routing on the Internet • Multicast Routing between Domains • Reference Multicast 3 Overview • Unicast • Multicast • Multicast Characteristic • IP Multicast Address • Examples of permanent groups • Architecture of Multicast Multicast 4 Unicast Host Router ． Point to point ． N receivers, send n times ． Not suitable for group communication Receiver Multicast 5 Multicast Host Router ． 1 sender and n receivers ． N receivers, only send 1 times ． Suitable for group communication Receiver Multicast 6 Benefits of Multicast • Saves bandwidth by enhancing network efficiency in distribution of data • Group communication and services • Supports distributed applications – distance learning – videoconferencing • Reduces the cost to deploy applications Multicast 7 Multicast Characteristic • RFC 1112 • Each multicast group identified by class- D IP address • Receivers can present anywhere • Receivers can join and leave anytime • Sender don’t need to be a member • No membership list exist, use routers to manage groups Multicast 8 IP Multicast Address • Multicast address range Class D IP Address-higher order 4 bits are set 224.0.0.0 239.255.255.255 1 1 1 0 Multicast address 1 1 0 Net ID 8 16 24 32 IP system 1 0 Net ID IP system 0 Net ID IP system Class D Class C Class B Class A Multicast 9 Examples of permanent groups All DVMRP routers in a subnet224.0.0.4 Not allocated224.0.0.3 Routers with RIP Version 2 in a subnet 224.0.0.9 All routers in a subnet224.0.0.2 All systems in a subnet224.0.0.1 Reserved224.0.0.0 Multicast 10 Architecture of Multicast Sender Router Receiver IGMP IGMP version 2 Multicast Routing [...]... manage group membership •Different Hosts may join more than one multicast group 12 IGMP – Join a Group Multicast Router Report Report Host 1 acitl u M 224.2.2.2 Host 2 Host 3 224.2.2.3 •Joining members sends report •Different hosts can join different multicast group 13 IGMP – General Query General query to 224.0.0.1 acitl u M Host 1 Host 2 Multicast Router Host 3 •Router periodically sends general query... as the actual Querier The other routers are Non-Querier 17 Outline acitl u M • • • • • Overview IGMP Multicast Routing on the Internet Multicast Routing between Domains Reference 18 Multicast Routing on the Internet acitl u M • • • • • DVMRP MOSPF PIM-DM PIM-SM CBT 19 DVMRP acitl u M • Distance Vector Multicast Routing Protocol (DVMRP) • Distance vector algorithm that determines the shortest path (hop... Trees(CBT) • Based on concept of rendezvous point, in this case called cores • Uses a bidirectional multicast tree acitl u M – PIM is unidirectional • Use of Hello mechanism • Restriction to one rendezvous point • Bootstrap mechanism 35 Outline acitl u M • • • • • Overview IGMP Multicast Routing on the Internet Multicast Routing between Domains Reference 36 ...Outline acitl u M • • • • • Overview IGMP Multicast Routing on the Internet Multicast Routing between Domains Reference 11 IGMP •Internet Group Management Protocol (IGMP) •Group management within edge networks •RFC 1112 – IGMP version 1 •RFC 2236 – IGMP version... Designated forwarder – First, lowest metric to a source – Second, lowest IP address 21 MOSPF • Multicast Extensions to Open Shortest Path First • OSPF – Hello – Synchronize database description – Link state advertisement acitl u M • MOSPF – Local group membership must be known in the routers – A separate multicast tree has to be calculated for each pair consisting of sender and group G(S,G) 22 MOSPF... • Protocol Independent MulticastingSparse Mode (PIM-SM) • Based on that systems are located far away from each other, density of group member is low=>B.W tends to be small • Membership is based on explicit join operations • Data is sent to the rendezvous point 31 PIM-SM (cont.) • Bootstrap routers distribute information about rendezvous points PIM router acitl u M PIM router Multicast border router... 224.0.0.1(all systems in a subnet) 14 IGMP – Maintaining a Group Multicast Router General query to 224.0.0.1 Report 224.2.2.2 Host 1 acitl u M 224.2.2.2 Host 2 Host 3 suppress 224.2.2.2 224.2.2.2 •Two steps: First, router sends general query Second, member send report •Only one member needs to send report 15 IGMP – Leaving a Group Multicast Router General query to 224.0.0.1 acitl u M Host 1 Host... each pair consisting of sender and group G(S,G) 22 MOSPF (cont.) Autonomous System Domain Boundary AS router BR AS R Domain BR Backbone R BR acitl u M Domain 23 PIM-DM acitl u M • Protocol Independent MulticastingDense Mode (PIM-DM) • Members are not widely distributed, density of group member is very high • Uses flooding, pruning and graft • Similar to DVMRP – Without the routing information exchange . needs to send report Multicast Router General query to 224.0.0.1 Multicast 16 IGMP – Leaving a Group Host 1 Host 2 Host 3 General query to 224.0.0.1 Multicast Router • Router continue to send. Internet • Multicast Routing between Domains • Reference Multicast 3 Overview • Unicast • Multicast • Multicast Characteristic • IP Multicast Address • Examples of permanent groups • Architecture of Multicast Multicast 4 Unicast Host Router ．. subnet224.0.0.1 Reserved224.0.0.0 Multicast 10 Architecture of Multicast Sender Router Receiver IGMP IGMP version 2 Multicast Routing Multicast 11 Outline • Overview • IGMP IGMP • Multicast Routing on the Internet • Multicast