mcast_unit3

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Chapter 15

Upon completion you will be able to:

Multicasting and

Multicast Routing Protocols

• Differentiate between a unicast, multicast, and broadcast message

• Know the many applications of multicasting

•Understand the Protocol Independent Multicast Protocols

•

Objectives


Figure 15.1 Unicasting

In unicasting, the router forwards the

received packet through only

one of its interfaces.


Figure 15.2 Multicasting

In multicasting, the router may forward the received packet

through several of its interfaces.


15.2 MULTICAST APPLICATIONS

Multicasting has many applications today such as access to distributed

databases, information dissemination, teleconferencing, and distance

learning.

The topics discussed in this section include:

Access to Distributed Databases

Information Dissemination

Dissemination of News

Teleconferencing

Distance Learning


15.3 MULTICAST ROUTING

In this section, we first discuss the idea of optimal routing, common in all

multicast protocols. We then give an overview of multicast routing

protocols.

The topics discussed in this section include:

Optimal Routing: Shortest Path Trees

Routing Protocols


Figure 15.4 Shortest path tree in unicast routing

In multicast routing, each involved router needs to

construct a shortest path tree for each group.


RPF eliminates the loop in the flooding

process.

Note:


Figure 15.8 RPF


Figure 15.9 Problem with RPF


Figure 15.10 RPF versus RPB


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.

Note:


Figure 15.11 RPF, RPB, and RPM


RPM adds pruning and grafting to RPB

to create a multicast shortest path tree

that supports dynamic membership

changes.

Note:

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