1. Autumn 2000John Kristoff1 Computer Networks IP Multicast

2. Autumn 2000John Kristoff2 Recall ÑUnicast ÑBroadcast ÑMulticast Ñsends to a specific group

3. Autumn 2000John Kristoff3 Unicast

4. Autumn 2000John Kristoff4 Multicast

5. Autumn 2000John Kristoff5 Introduction to IP Multicast ÑClass D group address (224-239.x.x.x) ÑFirst bits must be 1110 of first octet ÑHow to join/leave a multicast group? ÑHow to map to hardware address? ÑHow to route to a IP multicast group?

6. Autumn 2000John Kristoff6 IP Multicast Addressing ÑSome reserved addresses Ñ224.0.0.0/24 Link local reserved Ñe.g. 224.0.0.9 - RIPv2 routers Ñ239.0.0.0/8 Private (Administratively Scoped) ÑIP Multicast to ethernet multicast mapping Ñplace low-order 23 bits of IP address into low-order 23 bits of special Ethernet address 01:00:5e:00:00:00 Ñproblem... IP multicast has 28 significant bits!

7. Autumn 2000John Kristoff7 Internet Group Multicast Protocol (IGMP) ÑStandardized in RFC 1112 and 2236 ÑHost/Router signalling protocol ÑHosts send IGMP join messages ÑRouter periodically queries ÑIGMPv3 in draft ÑHosts only listen to specific group sources

8. Autumn 2000John Kristoff8 Multicast routing ÑBackwards from unicast routing ÑReverse Path Forwarding (RFP) ÑRoute away from source ÑCould follow the shortest (source tree) path ÑCould build a shared distribution tree ÑRendevous Point (RP) ÑDense (Push) and Sparse (Pull) Modes

9. Autumn 2000John Kristoff9 Distance Vector Multicast Routing Protocol (DVMRP) ÑSimilar to RIP ÑInfinity = 32 hops ÑFlood and Prune builds distribution tree ÑGrafting adds back a link ÑWas widely used in early MBONE ÑDoes not scale

10. Autumn 2000John Kristoff10 Multicast OSPF (MOSPF) ÑLSAs carry multicast route information ÑEach router learns entire multicast tree ÑOnly works with OSPF networks ÑDoes not scale well ÑNot popular

11. Autumn 2000John Kristoff11 Protocol Independent Multicast Dense Mode (PIM- DM) ÑUses any underlying routing protocol Ñe.g. RIP, OSPF, IS-IS, BGP, etc. ÑVery similar to DVMRP ÑFloods and prunes back based on membership ÑDoes not scale to large networks (MBONE)

12. Autumn 2000John Kristoff12 Protocol Independent Multicast Sparse Mode (PIM-SM) ÑSupports source and shared trees ÑUses a Rendevous Point (RP) ÑCan use any underlying routing protocol ÑTraffic only sent down joined branches ÑCan dynamically switch to optimal source tree depending on traffic pattern

13. Autumn 2000John Kristoff13 PIM-SM Illustrated

14. Autumn 2000John Kristoff14 Internet MBONE ÑMulticast backbone overlay on the Internet ÑOriginally used DVMRP, now mostly uses PIM-SM ÑFew commercial organizations using it ÑMany educational and research institutions using it

15. Autumn 2000John Kristoff15 Common MBONE Tools ÑSDR ÑVAT/RAT ÑVIC ÑWB ÑIP/TV ÑMtrace