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 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 Multicast address 110 Net ID IP system 10 Net ID IP system 0 Net IDIP system Class D Class C Class B Class A

Multicast 9 Examples of permanent groups All DVMRP routers in a subnet Not allocated Routers with RIP Version 2 in a subnet All routers in a subnet All systems in a subnet Reserved

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 Routing between Domains Reference

Multicast 12 IGMP Internet Group Management Protocol (IGMP) Group management within edge networks RFC 1112 – IGMP version 1 RFC 2236 – IGMP version 2 (widely uesd) Similar to the ICMP(Internet Control Message Protocol) Router sends query to their directly hosts to manage group membership Different Hosts may join more than one multicast group

Multicast 13 IGMP – Join a Group Joining members sends report Different hosts can join different multicast group Multicast Router Host 1Host 2Host Report

Multicast 14 IGMP – General Query Host 1Host 2Host 3 General query to Multicast Router Router periodically sends general query to (all systems in a subnet)

Multicast 15 IGMP – Maintaining a Group suppress Host 1Host 2Host Report Two steps:  First, router sends general query  Second, member send report Only one member needs to send report Multicast Router General query to

Multicast 16 IGMP – Leaving a Group Host 1Host 2Host 3 General query to Multicast Router Router continue to send general query periodically Members silently leave group No report receive by router Group times out

Multicast 17 IGMP - Querier Selection Host 1Host 2Host 3 MRouter MRouter Initially, all routers are querier and send query Then, only one router with the lowest IP address is selected as the actual Querier The other routers are Non-Querier

Multicast 18 Outline Overview IGMP Multicast Routing on the Internet Multicast Routing on the Internet Multicast Routing between Domains Reference

Multicast 19 Multicast Routing on the Internet DVMRP MOSPF PIM-DM PIM-SM CBT

Multicast 20 DVMRP Distance Vector Multicast Routing Protocol (DVMRP) Distance vector algorithm that determines the shortest path (hop count) Like RIP, maintains a routing table Uses RPF(Reverse Path Forwarding) –The first data is flooded to the entire network –No members or terminating membership, do pruning

Multicast 21 DVMRP (cont.) Graft is used to reconnect an old area or connect a new area –Member to source Graft ack. Indicates that a graft has been received correctly –Source to member Designated forwarder –First, lowest metric to a source –Second, lowest IP address

Multicast 22 MOSPF Multicast Extensions to Open Shortest Path First OSPF –Hello –Synchronize database description –Link state advertisement 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)

Multicast 23 MOSPF (cont.) Autonomous System BR R Boundary AS router R Domain Backbone AS

Multicast 24 PIM-DM Protocol Independent Multicasting- Dense 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 part –Differs in some details

Multicast 25 PIM-DM (cont.) Source B Receiver 1 C A D E Initial

Multicast 26 PIM-DM (cont.) Source B Receiver 1 C A D E Flooding

Multicast 27 PIM-DM (cont.) Source B Receiver 1 C A D E Pruning

Multicast 28 PIM-DM (cont.) Source B Receiver 1 C A D E Steady state

Multicast 29 PIM-DM (cont.) Source B Receiver 1 C A D E A receiver is joining Graft Receiver 2 Graft

Multicast 30 PIM-DM (cont.) Source B Receiver 1 C A D E Receiver 2 Steady state

Multicast 31 PIM-SM Protocol Independent Multicasting- Sparse 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

Multicast 32 PIM-SM (cont.) Bootstrap routers distribute information about rendezvous points PIM router Bootstrap router Multicast border router Non-PIM enabled domain PIM domain

Multicast 33 PIM-SM (cont.) Sender PIM Router 2 Receiver Data IGMP join PIM join PIM Router 1 Rendezvous PIM Router 3 PIM join PIM resister data unit

Multicast 34 PIM-SM (cont.) Sender PIM Router 2 Receiver PIM Router 1 Rendezvous PIM Router 3 delete PIM join Pruning data unit Data

Multicast 35 CBT Core-Based Trees(CBT) Based on concept of rendezvous point, in this case called cores Uses a bidirectional multicast tree –PIM is unidirectional Use of Hello mechanism Restriction to one rendezvous point Bootstrap mechanism

Multicast 36 Outline Overview IGMP Multicast Routing on the Internet Multicast Routing between Domains Multicast Routing between Domains Reference

Multicast 37 Multicast Routing Between Domains Multicast Domain BGMP Router Multicast Domain BGMP Router Multicast Domain BGMP Router Multicast Domain BGMP Router BGMP routing

Multicast 38 Multicast Routing Between Domains (cont.) BGMP( Border Gateway Multicast Protocol ) –Based on CBT and PIM-SM(avoid flooding) –BGMP join and prune data unit are transmitted over TCP –Multicast routing can throughout the internet by using BGMP –Connection between multicast domain autonomous system

Multicast 39 Reference Multicast Communication, writed by Ralph Wittmann and Martina Zitterbart, Morgan Kaufmann publish charter.html