©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl1 1 Chapter 14 Multicasting And Multicast Routing Protocols  INTRODUCTION  MULTICAST ROUTING  MULTICAST TREES  MULTICAST ROUTING PROTOCOLS  DVMRP  MOSPF  CBT  PIM  MBONE

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl2 2 Figure 14-1 In unicast routing, the router forwards the received packet through only one of its interfaces Introduction: Unicasting

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl3 3 Figure 14-2 Multicasting In multicast routing, the router may forward the received packet through several of its interfaces.

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl4 4 Figure 14-3 Multicasting versus multiple unicasting Emulation of multicasting through multiple unicasting is not efficient and may create long delays, particularly with a large group.

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl5 5 Application of Multicasting Access to Distributed Databases Information Dissemination: e.g. multicast software updates to customers News Delivery Teleconferencing, Web Seminars Distant Learning

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl Multicast Routing Objectives Every member receives EXACTLY ONE copy of the packet Non-members receive nothing No loops in route Optimal path from source to each destination. Terminology Spanning Tree: Source is the root, group members are the leaves. Shortest Path Spanning Tree: Each path from root to a leaf is the shortest according to some metric

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl Multicast Trees Source-Based Tree:  For each combination of (source, group), there is a shortest path spanning tree.  Approach 1: DVMRP; an extension of unicast distance vector routing (e.g. RIP)  Approach 2: MOSPF; an extension of unicast link state routing (e.g. OSPF) Group-Share Tree  One tree for the entire group  Rendezvous-Point Tree: one router is the center of the group and therefore the root of the tree. CBT and PIM-SP protocols.

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl8 8 Figure Multicast routing protocols

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl Distance Vector Multicast Routing Protocol - DVMRP No pre-defined route from source to destination. Tree is gradually created by successive routers along the path. Uses shortest path (fewest hops) Prevent loops: apply Reverse Path Forwarding (RFP) Prevent Duplication: apply Reverse Path Broadcasting (RPB) Multicast with dynamic membership: apply Reverse Path Multicasting (RPM) with pruning, grafting, and lifetime.

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl10 10 Figure 14-5 Reverse Path Forwarding In reverse path forwarding (RPF), the router forwards only the packets that have traveled the shortest path from the source to the router; all other copies are discarded. No Loops

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl11 11 Figure 14-6 Reverse Path Broadcasting Prevent Duplication in RPF

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl12 12 Figure 14-7 RPF versus RPB The router with the shortest path to the source becomes the designated parent of a network A Router forwards packets only to its designated child networks

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl13 13 RPB creates a shortest path broadcast tree from the source to each destination. It guarantees that each destination receives one and only one copy of the packet.

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl14 14 Figure 14-8 RPF, RPB, and RPM RPM adds pruning and grafting to RPB to create a multicast shortest path tree that supports dynamic membership changes.

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl15 15 MOSPF 14.6

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl16 16 Figure 14-9 Unicast tree and multicast tree

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl17 17 Core-Based Tree CBT 14.7

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl18 18 Figure Shared-group tree with rendezvous router

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl19 19 Figure Sending a multicast packet to the rendezvous router

©The McGraw-Hill Companies, Inc., 2000© Adapted for use at JMU by Mohamed Aboutabl, 2003Mohamed Aboutabl20 20 In CBT, the source sends the multicast packet (encapsulated in a unicast packet) to the core router. The core router decapsulates the packet and forwards it to all interested hosts.