MG H ©T MG H C I 20 Chapter 10 Internet Group Management Protocol (IGMP)
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Chapter 10
Internet GroupManagement Protocol
(IGMP)
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CONTENTS
• GROUP MANAGEMENT• IGMP MESSAGES• IGMP OPERATION• ENCAPSULATION• IGMP PACKAGE
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Figure 10-1
Position of IGMP in the network layer
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GROUP MANAGEMENT
10.1
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IGMP MESSAGES
10.2
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IGMP is a group management protocol. It helps a multicast router
create and update a list of loyal members related to
each router interface.
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Figure 10-2
IGMP message types
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Figure 10-3
IGMP message format
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IGMP OPERATION
10.3
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Figure 10-4
IGMP operation
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Figure 10-5
Membership report
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In IGMP, a membership report is sent twice,
one after the other.
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Figure 10-6 Leave report
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The general query message does not define a particular group.
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Figure 10-7
General query message
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Example 1
Imagine there are three hosts in anetwork as shown in Figure 10.8 (nextslide).
Imagine there are three hosts in anetwork as shown in Figure 10.8 (nextslide).A query message was received at time0; the random delay time (in tenths ofseconds) for each group is shown nextto the group address. Show thesequence of report messages.
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Figure 10-8 Example 1
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Solution
The events occur in this sequence:
Time 12: The timer for 228.42.0.0 in host Aexpires and a membership report is sent,which is received by the router and every hostincluding host B which cancels its timer for228.42.0.0.
Time 30: The timer for 225.14.0.0 in host Aexpires and a membership report is sent,which is received by the router and every hostincluding host C which cancels its timer for225 14 0 0
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Solution (Continued)
Time 50: The timer for 251.70.0.0 in host Cexpires and a membership report is sent,which is received by the router and everyhost.
Time 70: The timer for 230.43.0.0 in host Aexpires and a membership report is sent,which is received by the router and every hostincluding host A which cancels its timer for230.43.0.0.Note that if each host had sent a report for everygroup in its list, there would have been seven
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ENCAPSULATION
10.4
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Figure 10-9
Encapsulation of IGMP packet
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The IP packet that carries an IGMP packet has a value of
2in its protocol field.
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The IP packet that carries an IGMP packet has a value of
1in its TTL field.
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Figure 10-10
Mapping class D to Ethernet physical addres
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Figure 10-11
Tunneling
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IGMP PACKAGE
10.5
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Figure 10-12
IGMP package
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Figure 10-13
State: Free, Delaying, Idle
Reference Count: Number of processes interested
Group table
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