© 1999, Cisco Systems, Inc. 9-1 Chapter 10 Controlling Campus Device Access Chapter 9 Multicast Overview Multicast Overview © 1999, Cisco Systems, Inc. 10-1
Mar 26, 2015
© 1999, Cisco Systems, Inc. 9-1
Chapter 10
Controlling Campus Device Access
Chapter 9Chapter 9
Multicast OverviewMulticast OverviewMulticast OverviewMulticast Overview
© 1999, Cisco Systems, Inc. 10-1
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-2
Objectives
Upon completion of this chapter, you will be able to perform the following tasks:• Match the correct transmission method to the appropriate
definition
• Reconcile a set of IP multicast addresses to Ethernet addresses
• Describe the functional differences between IGMPv1 and IGMPv2
• Describe the setup procedure in which routers and switches facilitate multicast traffic
• Identify the appropriate multicast routing protocol for a given network requirement
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-3
Multicast Overview
• Multicast overview
• Addressing in a multicast environment
• Managing multicast traffic in a campus network
• Routing multicast traffic
• Multicast routing protocols
In this chapter, we discuss the following topics:
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-4
Multicast Overview
In this section, we discuss the following topics:• Multicast Overview
– Unicast Traffic
– Broadcast Traffic
– Multicast Traffic
– IP Multicast Characteristics• Addressing in a Multicast Environment
• Managing Multicast Traffic in a Campus Network
• Routing Multicast Traffic
• Multicast Routing Protocols
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-5
Unicast Traffic
VideoServer
Receiver Receiver Receiver Not AReceiver
• Unicast applications send one copy of each packet to every client unicast address
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-6
1.5 Mb x 3 = 4.5 Mb
1.5 Mb x 2 = 3 Mb 1.5 Mb x 1 = 1.5 Mb
1.5 Mb x 1 = 1.5 Mb
1.5 Mb x 1 = 1.5 Mb1.5 Mb x 1 = 1.5 Mb
Unicast Traffic (cont.)Unicast Traffic (cont.)
VideoServer
Receiver Receiver Receiver Not AReceiver
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-7
Unicast Traffic (cont.)
. . .
1.5 Mb x 100 = 150 Mb
1.5 Mb x 100 = 150 Mb
1.5 Mb x 100 = 150 Mb
Receiver 1 Receiver 100
1.5 Mb x 100 = 150 Mb
VideoServer
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-8
Broadcast Traffic
I don’t want to receive this video stream, but my CPU still needs to process that 1.5 MB
of data!
1.5 Mb
1.5 Mb 1.5 Mb
1.5 Mb 1.5 Mb 1.5 Mb 1.5 Mb
VideoServer
Receiver Receiver Receiver Not AReceiver
• Hosts not using a multimedia application must still process the broadcast traffic
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-9
Multicast Traffic
1.5 Mb
1.5 Mb 1.5 Mb
1.5 Mb 1.5 Mb 1.5 Mb
VideoServer
Receiver Receiver Receiver Not AReceiver
• A multicast server sends out a single data stream to multiple clients using a special broadcast address
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-10
IP Multicast Characteristics
• Transmits to a host group
• Delivers with “best effort” reliability
• Supports dynamic membership
• Supports diverse numbers and locations
• Supports membership in more than one group
• Supports multiple streams host
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-12
Multicast Overview
In this section, we discuss the following topics:• Multicast Overview
• Addressing in a Multicast Environment
– IP Multicasting Address Structure
–Mapping MAC addresses to IP Multicast Addresses
• Managing Multicast Traffic in a Campus Network
• Routing Multicast Traffic• Multicast Routing Protocols
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-13
Multicast IP Address Structure
• A Class D address consists of 1110 as the higher order bits in the first octet, followed by a 28-bit group address.
• Class D addresses range from 224.0.0.0 through 239.255.255.255. The high-order bits in the first octet identify this 224-base address.
Multicast Group ID1 1 01Class D
28 bits
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-14
Mapping IP Multicast to Ethernet Addresses
0000000100000000 011011110
Class D IP Address
48-Bit Ethernet Address
1110
0 7 8 15 16 23 24 31
Not
Used
Low-Order 23 Bits of Multi-cast
Group ID Copied to Ethernet Address
01 00 5E
224
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-15
0 0 0 0 1 0 10 0 0 0 0 1 0 00 0 0 0 0 0 1 01
224 10 8 5- - -
1 1 1 0 0 0 0 0
01 00- -
Multicast Address:
Ethernet Address:
Mapping Multicast to Ethernet Addresses: Example 1
Mapping Multicast to Ethernet Addresses: Example 1
5E 0A- 08- 05-
0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 1 0 1 1 1 1 0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 1
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-16
Mapping Multicast to Ethernet Addresses: Example 2
1 0 0 0 1 0 10 0 0 0 0 1 0 00 0 0 0 0 0 1 01
224 10 8 5- - -
1 1 1 0 1 0 1 0
01 00- -
Multicast Address:
Ethernet Address:
5E 0A- 08- 05-
0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 1 0 1 1 1 1 0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 1
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-17
Multicast Overview
In this section, we discuss the following topics:• Multicast Overview
• Addressing in a Multicast Environment
• Managing Multicast Traffic in a Campus Network
– Subscribing and Maintaining Groups
– IGMPv1
– IGMPv2
– Handling Multicast Trafficin the Switch
• Routing Multicast Traffic
• Multicast Routing Protocols
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-18
Facilitating Multimedia Traffic
• Coordinate multicast operations of network devices
• Establish a path between between source and destination
• Forward multicast traffic through the network
Source
Destination
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-19
Group Membership
Host A Host B Host C
Host DI’m not a
member so I won’t respond.
I’m a member so I will
respond.
I’m a member so I will
respond.
I’m a member so I will
respond.
Are there any members for Group XYZ?
• Multicast uses query and report messages to
establish and maintain group membership
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-20
IGMPv1—Packet Format
• Version Code Version = 1
• Type:– 1 = Host Membership Query– 2 = Host Membership Report
• Group Address:– Multicast Group Address
7 15 23 31
Ver Unused ChecksumType
4
Group Address
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-21
IGMPv1—Joining a Group
• Joining member sends report to 224.1.1.1 immediately upon joining
H3
224.1.1.1
Report
IGMPv1
H1 H2
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-22
IGMPv1—General Queries
• The router periodically sends general queries to 224.0.0.1 to determine memberships
General Query to 224.0.0.1
IGMPv1 MulticastRouter
H3H1 H2
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-23
IGMPv1—Maintaining a Group
IGMPv1
#1#1 Router sends periodic queries#2#2 One member per group per subnet report
224.1.1.1
#2#2
#3#3 Other members suppress reports
224.1.1.1
X#3#3
H3H1 H2
Query to224.0.0.1 #1#1
Report Suppressed
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-24
• Router sends periodic queries• Hosts silently leave group• Router continues sending periodic queries
Query to224.0.0.1
IGMPv1—Leaving a Group
IGMPv1
• No reports for group received by router• Group times out
H3H1 H2
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-25
IGMPv2—Packet Format
• Multiple message types
• Max. Resp. Time– Max. time before sending a responding report in 1/10 secs (default = 10 secs)
• Group Address:– Multicast Group Address (0.0.0.0 for General Queries)
Max. Resp. Time Checksum
Group Address
Type
7 15 31
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-26
IGMPv2—Joining a Group
• Joining member sends report to 224.1.1.1 immediately upon joining (same as IGMPv1)
224.1.1.1
Report
172.16.41.141
H1
172.16.41.1 172.16.41.2 172.16.41.3
RTR141
H3H2
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-27
IGMPv2—Joining a Group (cont.)
172.16.41.141
H1
172.16.41.1 172.16.41.2 172.16.41.3
RTR141
E0
H2 H3
RTR141>show ip igmp groupIGMP Connected Group MembershipGroup Address Interface Uptime Expires Last Reporter224.1.1.1 Ethernet0 6d17h 00:02:31 172.16.41.2
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-28
IGMPv2—Querier Election
• Intially all routers send out a query
• Router with lowest IP address “elected” querier
• Other routers become non-queriers
IGMPv2
H1 H2 H3
Query Query
IGMP QuerierIGMP
Non-Querier172.16.41.141
172.16.41.1 172.16.41.2 172.16.41.3
172.16.41.143
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-30
IGMPv2—Querier Election
• Locating the designated querier router
RTR141>show ip igmp interface e0Ethernet0 is up, line protocol is up Internet address is 172.16.41.141, subnet mask is 255.255.255.0 IGMP is enabled on interface Current IGMP version is 2 CGMP is disabled on interface IGMP query interval is 60 seconds IGMP querier timeout is 120 seconds IGMP max query response time is 10 seconds Inbound IGMP access group is not set Multicast routing is enabled on interface Multicast TTL threshold is 0 Multicast designated router (DR) is 172.16.41.141 (this system) IGMP querying router is 172.16.41.141 (this system) Multicast groups joined: 224.0.1.40 224.2.127.254
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-31
IGMPv2—Maintaining a Group
Router sends periodic queries
Query
IGMPv2
• One member per group per subnet report
224.1.1.1
Report
• Other members suppress reports
224.1.1.1
SuppressedX
H2 H3
172.16.41.141
172.16.41.1 172.16.41.2 172.16.41.3
H1
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-32
IGMPv2—Leaving a Group
H1 H2 H3
RTR141
• IGMP state in RTR141 before leave
172.16.41.1 172.16.41.2 172.16.41.3
172.16.41.141
RTR141>sh ip igmp groupIGMP Connected Group MembershipGroup Address Interface Uptime Expires Last Reporter224.1.1.1 Ethernet0 6d17h 00:02:31 172.16.41.2
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-33
IGMPv2—Leaving a Group (cont.)
• H2 leaves group; sends leave message
H1 H2 H3H2
Leave to224.0.0.2
224.1.1.1
#1#1
• Router sends group-specific query
Group SpecificQuery to 224.1.1.1
#2#2
• A remaining member host sends report;
Report to224.1.1.1
224.1.1.1
#3#3
group remains active
RTR141
172.16.41.1 172.16.41.2 172.16.41.3
172.16.41.141
#1#1
#2#2
#3#3
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-35
IGMPv2—Leaving a Group (cont.)
H1 H2 H3
RTR141
• IGMP state in RTR141 after H2 leaves
172.16.41.1 172.16.41.2 172.16.41.3
172.16.41.141
RTR141>sh ip igmp groupIGMP Connected Group MembershipGroup Address Interface Uptime Expires Last Reporter224.1.1.1 Ethernet0 6d17h 00:01:47 172.16.41.3
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-36
IGMPv2—Leaving a Group (Cont.)
• Last host leaves group; sends Leave message
H1 H3H3
Leave to224.0.0.2
224.1.1.1
#1#1
• Router sends group-specific query;
Group-specificQuery to 224.1.1.1
#2#2
no report is received, group times out
H2
#1#1
#2#2
RTR141
172.16.41.1 172.16.41.2 172.16.41.3
172.16.41.141
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-37
IGMPv2—Leaving a Group (cont.)
RTR141>sh ip igmp groupIGMP Connected Group MembershipGroup Address Interface Uptime Expires Last Reporter
H1 H2
RTR141
• IGMP state in RTR141 after H3 leaves
172.16.41.1 172.16.41.2 172.16.41.3
172.16.41.141
H3
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-38
Multicast Overview
In this section, we discuss the following topics:• Multicast Overview
• Addressing in a Multicast Environment
• Managing Multicast Traffic in a Campus Network Routing
–GCMP• Routing Multicast Traffic
• Multicast Routing Protocols
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-39
Layer 2 Multicast
I don’t want to receive this video stream, but my CPU still needs to process that 1.5 MB
of data!
1.5 Mb
1.5 Mb 1.5 Mb
1.5 Mb 1.5 Mb 1.5 Mb 1.5 Mb
Receiver Receiver Receiver Not A Receiver
VideoServer
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-40
CGMP
0000.0c12.3456
IGMP Join Request 0000.0c12.3456 would like to join multicast
group XYZ.
0000.0c12.3456 would like to join multicast
group XYZ.
• CGMP is a Cisco-developed protocol
• CGMP allows Catalyst switches to learn about the existence of multicast clients from Cisco routers
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-41
CGMP (cont.)
Device 0000.0c12.3456wants to join
Group 234.10.8.5
Device 0000.0c12.3456wants to join
Group 234.10.8.5
CGMP Message
0000.0c12.3456
CGMP Message
I have no knowledge of
device 0000.0c12.3456
I have no knowledge of
device 0000.0c12.3456
I can reach device0000.0c12.3456
out of Port 1. I will add 234.10.8.5 to my switch
forwarding table.
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-42
Multicast Overview
In this section, we discuss the following topics:• Multicast Overview
• Addressing in a Multicast Environment
• Managing Multicast Traffic in a Campus Network
• Routing Multicast Traffic–Routing Protocols
–Distribution Trees
–Scope of Delivery• Multicast Routing Protocols
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-43
Unicast Routing
Host A172.13.107.5
Network172.13.0.0
Network172.45.0.0
Server B172.45.37.10
172.13.107.5 172.45.37.10
DestinationAddress
SourceAddress
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-44
Multicast Routing
Host A172.13.107.5
Host B172.45.37.10
Network172.45.0.0
Network172.45.0.0
Network172.6.0.0
B
I don’t have anyclients in group 234.10.8.5 but Router B has.
I don’t have anyclients in group 234.10.8.5 but Router B has. A
01-00-5e-10-8-5234.10.8.5Multimedia Stream for Group XYZ
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-45
Distribution Trees
I am a member of Group XYZ.
I am a member of Group XYZ.
I am a member of Group XYZ.
I am a member of Group XYZ.
I am NOT member of Group XYZ.
I am NOT member of Group XYZ.
Packet Duplicationat This Point Only
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-47
Source Distribution Tree
Server 1Group ABC
Host 1Group ABC
A B C D
E F G
• Source-specific trees use the shortest path from the sender to each receiver
Host 2Group ABC
Host 3Group ABC
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-48
Source Distribution Tree (cont.)
Server 1Group ABC
Host 1Group ABC
A B C D
E F G
Host 2Group ABC
• If the link between the local router and the neighboring router is not the shortest path, the packet is not forwarded on that link
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-49
Shared Distribution Tree
Source 1
A B C D
E F G
Source 2
• Multicast traffic for each group is sent and received over the same delivery tree, regardless of the source
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-51
Scope of Delivery
Acme Manufacturing, Inc.
Human Resources
EngineeringPersonnel Payroll
TTL Threshold = 15
TTL Threshold = 31TTL Threshold = 127
• Assigning a TTL threshold to each interface limits the scope of multicast transmission
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-52
Time To Live Threshold
E0 E1
E2E3
E1: (TTL Threshold = 16)E2: (TTL Threshold = 0)E3: (TTL Threshold = 64)
Multicast Packetw/TTL=24
Packet Not Forwarded!
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-53
Multicast Overview
In this section, we discuss the following topics:• Multicast Overview
• Addressing in a Multicast Environment
• Managing Multicast Traffic in a Campus Network
• Routing Multicast Traffic• Multicast Routing Protocols
–Dense Mode Routing Protocols
–Sparse Mode Routing Protocols
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-54
Dense Mode Routing Protocols
• Densely distributed receivers• Plentiful bandwidth• Majority of routers forwarding multicast traffic• Protocols– DVMRP– MOSPF– PIM DM
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-56
Distance Vector Multicast Routing Protocol
This is amulticast packet for Group XYZ.
This is amulticast packet for Group XYZ.
• Reverse path flooding floods a packet on all paths except the path leading back to the source.
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-57
Multicast Open Shortest Path First (MOSPF)
I have a newmember for Group XYZ.
I have a newmember for Group XYZ.
Source 1
Group XYZ
A B C D
E F G
Group XYZ
DesignatedRouter
Router F has a new member for Group XYZ.
Router F has a new member for Group XYZ.
• Uses OSPF link-state advertisements to construct distribution trees
• Trees must be recomputed when a link-state change occurs
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-58
Protocol Independent Multicast Dense Mode (PIM DM)
This is a multicast packet for Group XYZ.
This is a multicast packet for Group XYZ.
• Protocol-independent means the protocol is not dependent
on any unicast routing protocol
I have nomembers forGroup XYZ.
I have nomembers forGroup XYZ.
Prune Message
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-60
Sparse-Mode Routing Protocols
• Sparsely distributed receivers• Limited bandwidth• Add branches as a result of
explicit joins• Protocols– CBT– PIM SM
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-61
Core-Based Tree
Core Router
I have a memberwho wants to join
Group XYZ.
I have a memberwho wants to join
Group XYZ.
AB
C D E
Join Message
Source 1
Join Message
Source 2
• CBT protocol constructs a single tree shared by all members of the group
• A CBT shared tree has a core router that is used to construct the tree
I am already abranch of that tree.I will acknowledge the join message.
I am already abranch of that tree.I will acknowledge the join message.
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-62
Protocol Independent Multicast Sparse Mode (PIM SM)
Rendezvous Point
I want to start receiving
multicast packetsto Group XYZ
I want to start receiving
multicast packetsto Group XYZ
A
C
BD
Optimized Path
InitialPath
InitialPath
I want to start sending
multicast packetsto Group XYZ
I want to start sending
multicast packetsto Group XYZ
InitialPath
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-64
Written ExerciseWritten Exercise
• Following is the written exercise for this chapter
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-65
Summary
• Multicast is the most efficient method for data transmission to multiple client.
• IP Multicast employs special addressing.
• IGMP allows clients to join and leave multicast groups.
• CGMP allows switches to handle multicast traffic.
• Special routing protocols are used to route multicast traffic through the network.
• Multicast routing protocols are divided into two categories.
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-66
Review
• Discuss the three types of transmission methods and the effect each one has on network bandwidth.
• Explain how routers and switches handle the impact of multicast addressing techniques.
• Discuss different multicast routing protocols and identify which ones are most effective in a campus network.