Transcript Lesson8

Chapter
10
Chapter 9
Controlling Campus
Multicast Overview
Device Access
© 1999, Cisco Systems, Inc.
10-1
9-1
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—9-2
Multicast Overview
In this chapter, 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
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-3
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—9-4
Unicast Traffic
Video
Server
Receiver
Receiver
Receiver
Not A
Receiver
• Unicast applications send one copy of each packet to every client
unicast address
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-5
Unicast Traffic (cont.)
1.5 Mb x 3 = 4.5 Mb
Video
Server
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 Mb
Receiver
© 1999, Cisco Systems, Inc.
1.5 Mb x 1 = 1.5 Mb
Receiver
Receiver
www.cisco.com
Not A
Receiver
BCMSN—9-6
Unicast Traffic (cont.)
1.5 Mb x 100 = 150 Mb
1.5 Mb x 100 = 150
Mb
Video
Server
1.5 Mb x 100 = 150 Mb
1.5 Mb x 100 = 150 Mb
...
Receiver 1
© 1999, Cisco Systems, Inc.
Receiver 100
www.cisco.com
BCMSN—9-7
Broadcast Traffic
1.5 Mb
Video
Server
1.5 Mb
1.5 Mb
Receiver
1.5 Mb
Receiver
1.5 Mb
1.5 Mb
Receiver
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
Not A
Receiver
• Hosts not using a multimedia application must still process the
broadcast traffic
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-8
Multicast Traffic
1.5 Mb
Video
Server
1.5 Mb
1.5 Mb
Receiver
1.5 Mb
Receiver
1.5 Mb
1.5 Mb
Receiver
Not A
Receiver
• 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—9-9
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—9-10
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—9-12
Multicast IP Address Structure
28 bits
Class D
1
1
1
0
Multicast Group ID
• 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.
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-13
Mapping IP Multicast to
Ethernet Addresses
0
7 8
15 16
23 24
31
Class D IP Address 1110
224
Not
Low-Order 23 Bits of Multi-cast
Used Group ID Copied to Ethernet Address
01
00
5E
0000000100000000 11011110 0
48-Bit Ethernet Address
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-14
Mapping Multicast to Ethernet
Addresses: Example 1
Multicast Address:
224
-
10
-
8
-
5
1 1 1 0 0 0 0 0 0 0 0 0 1 0 10 0 0 0 0 1 0 00 0 0 0 0 0 1 01
Ethernet Address:
01
-
00
-
5E
-
0A
-
08
-
05
000000010000000011011110000010100000100000000101
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-15
Mapping Multicast to Ethernet
Addresses: Example 2
Multicast Address:
224
-
10
-
8
-
5
1 1 1 0 1 0 1 0 1 0 0 0 1 0 10 0 0 0 0 1 0 00 0 0 0 0 0 1 01
Ethernet Address:
01
-
00
-
5E
-
0A
-
08
-
05
000000010000000011011110000010100000100000000101
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-16
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 Traffic
in the Switch
• Routing Multicast Traffic
• Multicast Routing Protocols
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-17
Facilitating Multimedia Traffic
• Coordinate multicast
operations of network devices
Source
• Establish a path between
between source and destination
• Forward multicast traffic
through the network
© 1999, Cisco Systems, Inc.
www.cisco.com
Destination
BCMSN—9-18
Group Membership
Are there any
members for
Group XYZ?
Host D
Host A
I’m a member
so I will
respond.
Host B
I’m not a
member so I
won’t respond.
Host C
I’m a member
so I will
respond.
I’m a member
so I will
respond.
• Multicast uses query and report messages to
establish and maintain group membership
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-19
IGMPv1—Packet Format
4
7
Ver Type
15
Unused
23
31
Checksum
Group Address
• Version Code Version = 1
• Type:
– 1 = Host Membership Query
– 2 = Host Membership Report
• Group Address:
– Multicast Group Address
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-20
IGMPv1—Joining a Group
H1
Report
H2
H3
224.1.1.1
IGMPv1
• Joining member sends report to 224.1.1.1
immediately upon joining
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-21
IGMPv1—General Queries
H1
H2
H3
General Query
to 224.0.0.1
IGMPv1
Multicast
Router
• The router periodically sends general queries to
224.0.0.1 to determine memberships
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-22
IGMPv1—Maintaining a Group
224.1.1.1
H1
H2
Report
#2
#2
#3
X
Suppressed
Query to
224.0.0.1
IGMPv1
#1
224.1.1.1
H3
#3
#1
Router sends periodic queries
One member per group per subnet report
Other members suppress reports
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-23
IGMPv1—Leaving a Group
H1
H2
H3
Query to
224.0.0.1
IGMPv1
• Router sends periodic queries
• Hosts silently leave group
• Router continues sending periodic queries
• No reports for group received by router
• Group times out
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-24
IGMPv2—Packet Format
7
Type
15
Max. Resp. Time
31
Checksum
Group Address
• 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)
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-25
IGMPv2—Joining a Group
172.16.41.1
H1
172.16.41.2
224.1.1.1
H2
172.16.41.3
H3
Report
172.16.41.141
RTR141
• Joining member sends report to 224.1.1.1
immediately upon joining (same as IGMPv1)
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-26
IGMPv2—Joining a Group
(cont.)
172.16.41.1
H1
172.16.41.2
172.16.41.3
H2
H3
172.16.41.141
E0
RTR141
RTR141>show ip igmp group
IGMP Connected Group Membership
Group Address
Interface
Uptime
224.1.1.1
Ethernet0
6d17h
© 1999, Cisco Systems, Inc.
www.cisco.com
Expires
00:02:31
Last Reporter
172.16.41.2
BCMSN—9-27
IGMPv2—Querier Election
172.16.41.1
H1
172.16.41.2
H2
172.16.41.3
H3
Query
Query
IGMP
IGMP Querier
Non-Querier
IGMPv2
172.16.41.143
172.16.41.141
• Intially all routers send out a query
• Router with lowest IP address “elected” querier
• Other routers become non-queriers
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-28
IGMPv2—Querier Election
RTR141>show ip igmp interface e0
Ethernet0 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
• Locating the designated querier router
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-30
IGMPv2—Maintaining a Group
172.16.41.1
H1
172.16.41.2
224.1.1.1
H2
172.16.41.3
224.1.1.1
H3
X
Report
Suppressed
Query
IGMPv2
172.16.41.141
Router sends periodic queries
• One member per group per subnet report
• Other members suppress reports
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-31
IGMPv2—Leaving a Group
172.16.41.1
172.16.41.2
172.16.41.3
H1
H2
H3
RTR141
RTR141>sh ip igmp group
IGMP Connected Group Membership
Group Address
Interface
Uptime
224.1.1.1
Ethernet0
6d17h
Expires
00:02:31
172.16.41.141
Last Reporter
172.16.41.2
• IGMP state in RTR141 before leave
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-32
IGMPv2—Leaving a Group
(cont.)
172.16.41.1
H1
172.16.41.2
224.1.1.1
Leave to
#1 224.0.0.2
172.16.41.3
224.1.1.1
H2
H3
Report to
#3 224.1.1.1
RTR141
172.16.41.141
Group Specific
Query to 224.1.1.1
#2
#1
•
H2 leaves group; sends leave message
#2
• Router sends group-specific query
#3
• A remaining member host sends report;
group remains active
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-33
IGMPv2—Leaving a Group
(cont.)
172.16.41.1
172.16.41.2
172.16.41.3
H1
H2
H3
RTR141
RTR141>sh ip igmp group
IGMP Connected Group Membership
Group Address
Interface
Uptime
224.1.1.1
Ethernet0
6d17h
Expires
00:01:47
172.16.41.141
Last Reporter
172.16.41.3
• IGMP state in RTR141 after H2 leaves
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-35
IGMPv2—Leaving a Group
(Cont.)
172.16.41.1
H1
172.16.41.2
172.16.41.3
224.1.1.1
H2
H3
Leave to
#1 224.0.0.2
RTR141
172.16.41.141
Group-specific
Query to 224.1.1.1
#2
#1
•
Last host leaves group; sends Leave message
• Router sends group-specific query;
#2
no report is received, group times out
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-36
IGMPv2—Leaving a Group
(cont.)
172.16.41.1
172.16.41.2
172.16.41.3
H1
H2
H3
RTR141
RTR141>sh ip igmp group
IGMP Connected Group Membership
Group Address
Interface
Uptime
Expires
172.16.41.141
Last Reporter
• IGMP state in RTR141 after H3 leaves
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-37
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—9-38
Layer 2 Multicast
1.5 Mb
Video
Server
1.5 Mb
1.5 Mb
Receiver
© 1999, Cisco Systems, Inc.
1.5 Mb
Receiver
1.5 Mb
1.5 Mb
Receiver
www.cisco.com
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
Not A
Receiver
BCMSN—9-39
CGMP
0000.0c12.3456
would like to
join multicast
group XYZ.
0000.0c12.3456
• 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—9-40
CGMP (cont.)
I can reach device
0000.0c12.3456
out of Port 1. I will
add 234.10.8.5
to my switch
forwarding table.
Device
0000.0c12.3456
wants to join
Group 234.10.8.5
I have no
knowledge of
device
0000.0c12.3456
0000.0c12.3456
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-41
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—9-42
Unicast Routing
Destination
Address
Source
Address
172.13.107.5
172.45.37.10
Server B
172.45.37.10
Network
172.45.0.0
Network
172.13.0.0
Host A
172.13.107.5
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-43
Multicast Routing
Multimedia Stream for Group XYZ
234.10.8.5 01-00-5e-10-8-5
Network
172.6.0.0
I don’t have any
clients in group
234.10.8.5 but
Router B has.
A
B
Network
172.45.0.0
Network
172.45.0.0
Host A
172.13.107.5
© 1999, Cisco Systems, Inc.
Host B
172.45.37.10
www.cisco.com
BCMSN—9-44
Distribution Trees
Packet Duplication
at This Point Only
I am a
member of
Group XYZ.
© 1999, Cisco Systems, Inc.
I am a
member of
Group XYZ.
www.cisco.com
I am NOT
member of
Group XYZ.
BCMSN—9-45
Source Distribution Tree
Server 1
Group ABC
A
B
C
E
F
G
Host 1
Group ABC
Host 2
Group ABC
Host 3
Group ABC
D
• Source-specific trees use the shortest path from
the sender to each receiver
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-47
Source Distribution Tree
(cont.)
Server 1
Group ABC
A
B
E
F
Host 1
Group ABC
Host 2
Group ABC
C
D
G
• 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—9-48
Shared Distribution Tree
Source 1
Source 2
A
E
B
F
C
D
G
• 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—9-49
Scope of Delivery
Acme Manufacturing, Inc.
Human Resources
Personnel
Payroll
Engineering
TTL Threshold = 15
TTL Threshold = 31
TTL Threshold = 127
• Assigning a TTL threshold to each interface limits the
scope of multicast transmission
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-51
Time To Live Threshold
Multicast Packet
w/TTL=24
E0
Packet Not
Forwarded!
© 1999, Cisco Systems, Inc.
E3
E1: (TTL Threshold = 16)
E2: (TTL Threshold = 0)
E3: (TTL Threshold = 64)
E1
E2
www.cisco.com
BCMSN—9-52
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—9-53
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—9-54
Distance Vector Multicast
Routing Protocol
This is a
multicast 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—9-56
Multicast Open Shortest Path
First (MOSPF)
Source 1
Designated
Router
A
E
Router F has
a new member
for Group XYZ.
B
C
F
D
G
I have a new
member for
Group XYZ.
Group XYZ
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—9-57
Protocol Independent Multicast
Dense Mode (PIM DM)
This is a
multicast packet
for Group XYZ.
Prune Message
I have no
members for
Group XYZ.
• Protocol-independent means the protocol is not dependent
on any unicast routing protocol
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-58
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—9-60
Core-Based Tree
Source 1
Core
Router
Source 2
B
A
Join
Message
C
I am already a
branch of that tree.
I will acknowledge
the join message.
D
E
Join
Message
I have a member
who wants to join
Group XYZ.
• 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
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-61
Protocol Independent Multicast
Sparse Mode (PIM SM)
I want to
start receiving
multicast packets
to Group XYZ
I want to
start sending
multicast packets
to Group XYZ
Optimized
Path
A
Initial
Path
Rendezvous
Point
D
B
Initial
Path
© 1999, Cisco Systems, Inc.
C
www.cisco.com
Initial
Path
BCMSN—9-62
Written Exercise
• Following is the written exercise for this chapter
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-64
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—9-65
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.
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—9-66