Multicasting and Multicast Routing Protocol
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Transcript of Multicasting and Multicast Routing Protocol
1©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200311
Chapter 14
Multicasting And MulticastRouting Protocols
INTRODUCTION MULTICAST ROUTING MULTICAST TREES MULTICAST ROUTING PROTOCOLS DVMRP MOSPF CBT PIM MBONE
2©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200322
Figure 14-1
In unicast routing, the router forwards
the received packet through
only one of its interfaces.
14.1 Introduction: Unicasting
3©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200333
Figure 14-2
Multicasting
In multicast routing, the router may forward the
received packet through several of its interfaces.
4©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200344
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.
5©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200355
Application of Multicasting
Access to Distributed Databases Information Dissemination: e.g. multicast software updates to
customers News Delivery Teleconferencing, Web Seminars Distant Learning
6©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200366
14.3 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
7©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200377
14.3 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.
8©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200388
Figure 14-4
14.4 Multicast routing protocols
9©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200399
14.5 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.
10©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 20031010
Figure 14-5
Reverse Path ForwardingIn 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
11©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 20031111
Figure 14-6
Reverse Path BroadcastingPrevent Duplication in RPF
12©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 20031212
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
13©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 20031313
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.
14©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 20031414
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.
15©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 20031515
MOSPF
14.614.6
16©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 20031616
Figure 14-9
Unicast tree and multicast tree
17©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 20031717
Core-Based TreeCBT
14.714.7
18©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 20031818
Figure 14-10
Shared-group tree with rendezvous router
19©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 20031919
Figure 14-11Sending a multicast packet to
the rendezvous router
20©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 20032020
In CBT, the source sends the In CBT, the source sends the multicast packet (encapsulated in a multicast packet (encapsulated in a unicast packet) to the core router. unicast packet) to the core router. The core router decapsulates the The core router decapsulates the
packet and forwards it packet and forwards it to all interested hosts. to all interested hosts.