BRKIPM-1261-rev5
Introduction to IP
Multicast
Beau Williamson
CCIE R/S #1346 Emeritus
CiscoLive Distinguished Speaker
Twitter: @Mr_Multicast
BRKIPM-1261
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Other IP Multicast Sessions @ CiscoLive
•
BRKIPM-2264 – Troubleshooting Multicast
•
•
BRKIPM-2249 – Segment Routing and Multicast
•
•
Monday, Jun 26, 8:00 a.m. - 12:00 p.m. | MGM Grand, Level 1, Room 108
BRKIPM-3017 – Advanced mVPN Deployment Models
•
•
M,Tu,W,Th, 10:00 a.m. - 10:45 a.m. | WISP 78
LTRMPL-3103 – Next Generation Multicast VPN
•
•
M,Tu,W,Th, 10:00 a.m. - 10:45 a.m. | WISP 77
LABMPL-2005 – Introduction to Multicast Label Distribution (mLDP)
•
•
Monday, Jun 26, 4:00 p.m. - 5:30 p.m. | Level 3, Palm D
LABCCIE-3010 – CCIE SP - Multicast VPN
•
•
Wednesday, Jun 28, 8:00 a.m. - 10:00 a.m. | Level 2, Mandalay Bay A
Tuesday, Jun 27, 4:00 p.m. - 5:30 p.m. | Level 3, South Seas
BRKSPV-2919 – Video Transport Architectures
•
Wednesday, Jun 28, 1:30 p.m. - 3:30 p.m. | Level 2, Reef B
BRKIPM-1261
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4
Session Goals
•
To provide you with an
understanding of the concepts,
mechanics and protocols used to
build IP multicast networks.
•
To enable you to ask the right
questions, and make the correct
architectural decisions in deploying
and maintaining an IP Multicast
enabled network.
•
To prove that Multicast doesn’t
have to be:
•
Hard
• Scary
BRKIPM-1261
Agenda
•
Multicast Fundamentals
• Source-Specific Multicast (SSM)
• Bidirectional Multicast (Bidir)
• Any-Source Multicast (ASM)
• ASM Redundant RP Choices
• Multicast at Layer 2
• Multicast over MPLS – mLDP
• Bit-Indexed Explicit Replication –
BIER
• Inter-domain IP Multicast
• IPv6 Multicast
Geekometer
BRKIPM-1261
Multicast Fundamentals
BRKIPM-1261
7
Why Multicast
Unicast vs. Multicast Scaling
Unicast
Server
Router
Number of Streams
Multicast
Server
Router
BRKIPM-1261
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8
Multicast Uses
•
Any applications with multiple receivers
•
One-to-many or many-to-many
•
Live video distribution
•
Collaborative groupware
•
Periodic data delivery—“push” technology
•
•
Stock quotes, sports scores, magazines,
newspapers, adverts
Inter Data Center L2 Underlay
•
VXLAN, etc. for BUM
•
Server/Website replication
•
Reducing network/resource
overhead
•
More than multiple point-to-point flows
•
Resource discovery
•
Distributed interactive simulation
(DIS)
•
War games
• Virtual reality
BRKIPM-1261
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9
Multicast Considerations
Multicast Is UDP-Based
•
Best effort delivery: Drops are to be expected; multicast applications should not expect
reliable delivery of data and should be designed accordingly; reliable multicast is still an
area for much research; expect to see more developments in this area; PGM, FEC, QoS
•
No congestion avoidance: Lack of TCP windowing and “slow-start” mechanisms can
result in network congestion; if possible, multicast applications should attempt to detect
and avoid congestion conditions
•
Duplicates: Some multicast protocol mechanisms (e.g., asserts, registers, and SPT
transitions) result in the occasional generation of duplicate packets; multicast applications
should be designed to expect occasional duplicate packets
•
Out of order delivery: Some protocol mechanisms may also result in out of order delivery
of packets
BRKIPM-1261
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10
Multicast Fundamentals
Multicast Myth Busters
“Multicast is complicated, scary and hard
to understand!”
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11
Unicast vs. Multicast Addressing
12.1.1.1
11.1.1.1
src addr:
10.1.1.1
src addr:
10.1.1.1
A unique packet
addressed to each
destination IP Address.
13.1.1.1
Multicast
Group
Address
e.g. 224.1.1.1
Same packet
addressed to “Group”
destination address...
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12
Unicast vs. Multicast Addressing
12.1.1.1
11.1.1.1
src addr:
10.1.1.1
src addr:
10.1.1.1
A unique packet
addressed to each
destination IP Address.
13.1.1.1
Multicast
Group
Address
e.g. 224.1.1.1
..replicated at each
node along the
tree.
BRKIPM-1261
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13
Multicast
MulticastAddressing
Addressing
IPv4 Header
Version
IHL
Type of Service
Identification
Time to Live
Total Length
Flags
Protocol
Fragment Offset
Header Checksum
Source
Source
Source Always
Addressthe unique unicast origin address of
the packet – same as unicast
1.0.0.0 - 232.255.255.255 (Class A, B, C)
Destination
Destination
Destination Address
224.0.0.0 - 239.255.255.255 (Class D) Multicast Group
Options
Address Range
Padding
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14
Multicast Addressing
Class D Group addresses – 224/4
•
Multicast Group addresses are NOT in the unicast route table.
•
A separate multicast route table is maintained for active multicast trees.
•
Multicast trees are initiated by receivers signaling their request to join a group.
•
Sources do not need to join, they just send!
•
Multicast routing protocols build the trees:
•
Hop-by-hop, from the receivers (tree leaves) to the source (tree root).
• Tree path follows the unicast route table backward to the source using source address.
•
i.e. Multicast relies on a dependable unicast infrastructure!
BRKIPM-1261
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15
Multicast Addressing—224/4
•
Reserved link-local addresses
•
•
•
224.0.0.0–224.0.0.255
Transmitted with TTL = 1
Examples
•
•
•
•
•
•
224.0.0.1
224.0.0.2
224.0.0.5
224.0.0.13
224.0.0.22
All systems on this subnet
All routers on this subnet
OSPF routers
PIMv2 routers
IGMPv3
Other IANA reserved addresses
•
•
•
224.0.1.0–224.0.1.255
Not local in scope (transmitted with TTL > 1)
Examples
•
•
•
224.0.1.1
224.0.1.32
224.0.1.78
NTP (Network Time Protocol)
Mtrace routers
Tibco Multicast1
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16
Multicast Addressing—224/4
•
Administratively scoped addresses
•
239.0.0.0–239.255.255.255
• Private address space
•
•
•
Similar to RFC1918 unicast addresses
Not used for global Internet traffic—scoped traffic
SSM (Source Specific Multicast) range
•
232.0.0.0–232.255.255.255
• Primarily targeted for Internet-style broadcast
BRKIPM-1261
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17
Multicast Addressing
IP Multicast MAC Address Mapping
32 Bits
28 Bits
1110
239.255.0.1
5 Bits
Lost
01-00-5e-7f-00-01
25 Bits
23 Bits
48 Bits
BRKIPM-1261
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18
Multicast Addressing
IP Multicast MAC Address Mapping
Be Aware of the 32:1 Address Overlap
32–IP Multicast Addresses
224.1.1.1
224.129.1.1
225.1.1.1
225.129.1.1
.
.
.
238.1.1.1
238.129.1.1
239.1.1.1
239.129.1.1
1–Multicast MAC Address
0x0100.5E01.0101
BRKIPM-1261
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19
How are Multicast Flows Identified
•
Every Multicast Flow can be identified by two components:
•
Source IP Address
•
•
Multicast Group Address
•
•
The address of the Sender
224/4 (Class D) IP Address
Multicast Flow from Source 2.2.2.2 to
Group 232.1.1.1
Example
(2.2.2.2, 232.1.1.1), 3w1d/00:02:40, flags: s
Incoming interface: Ethernet 0/0, RPF nbr 207.109.83.33
Outgoing interface list:
Ethernet 1/0, Forward/Sparse, 3w1d/00:02:40
Ethernet 2/0, Forward/Sparse, 2w0d/00:02:33
•
How do Hosts Signal to Routers which flow they want?
•
IPv4: IGMP
• IPv6: MLD
BRKIPM-1261
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20
Host-Router Signaling: IGMP
•
IGMP Version 3 is current version
•
•
RFC3376 Oct 2002 (Over 10 years old!)
Uses 224.0.0.22 (IGMPv3 routers) Link-Local Multicast Address
•
All IGMP hosts send Membership Reports to this address
• All IGMP routers listen to this address
• Hosts do not listen or respond to this address (unlike previous IGMP versions)
•
Membership Reports
•
Sent by Hosts
• Contain list of Multicast (Source, Group) pairs to Include/Exclude (Join/Leave)
•
Membership Queries
•
Sent by Routers to refresh/maintain list of Multicast traffic to deliver.
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21
IGMPv3 – Membership Report Packet Format
7
Type = 0x22
15
Reserved
31
Checksum
Reserved
# of Group Records (M)
7
15
Record Type Aux Data Len
31
# of Sources (N)
Multicast Group Address
Group Record [1]
Source Address [1]
Source Address [2]
.
.
Source Address [N]
Group Record [2]
.
.
.
Auxiliary Data
Group Record [M]
# of Group Records (M)
Number of Group Records in Report
Group Records 1 - M
Group address plus list of zero or
more sources to Include/Exclude
(See Group Record format)
Record Type
Include, Exclude, Chg-to-Include,
Chg-to-Exclude, Allow New Srcs,
Block Old Srcs
# of Sources (N)
Number of Sources in Record
Source Address 1- N
Address of Source
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IGMPv3 – Query Packet Format
Type = 0x11
IGMP Query
Max. Resp. Time
Max. time to send a response
if < 128, Time in 1/10 secs
if > 128, FP value (12.8 - 3174.4 secs)
Group Address:
Multicast Group Address
(0.0.0.0 for General Queries)
7
Type = 0x11
15
31
Max. Resp.
Code
Checksum
Group Address
S QRV
QQIC
Number of Sources (N)
S Flag
Suppresses processing by routers
Source Address [1]
QRV (Querier Robustness Value)
Affects timers and # of retries
Source Address [2]
.
.
.
QQIC (Querier’s Query Interval)
Same format as Max. Resp. Time
Number of Sources (N)
(Non-zero for Group-and-Source Query)
Source Address [N]
Source Address
Address of Source
BRKIPM-1261
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23
IGMPv3 – Joining Group “G” Source “S”
192.168.102.10
192.168.102.11
H1
H2
192.168.102.12
Type: Allow New (5)
Group: 232.1.1.1
Source: {2.2.2.2}
Report
(224.0.0.22)
H3
show ip igmp groups 232.1.1.1 detail
Flags: L - Local, U - User, SG - Static Group, VG - Virtual Group,
SS - Static Source, VS - Virtual Source,
Ac - Group accounted towards access control limit
Interface: GigabitEthernet3/3
Group:
232.1.1.1
Flags:
SSM
Uptime:
00:01:14
Group mode: INCLUDE
Last reporter:
192.168.102.11
Group source list: (C - Cisco Src Report, U - URD, R - Remote, S - Static,
V - Virtual, M - SSM Mapping, L - Local,
Ac - Channel accounted towards access control limit)
Source Address
Uptime
v3 Exp
CSR Exp
Fwd Flags
2.2.2.2
00:01:14 00:02:08 stopped
Yes R
Hn
Member
Group: 232.1.1.1
Source: 2.2.2.2
(Destination IP Address)
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24
IGMPv3 – Maintaining State
192.168.102.10
H1
192.168.102.11
Type: Include (1)
Group: 232.1.1.1
Source: {2.2.2.2}
Report
(224.0.0.22)
H2
192.168.102.12
Type: Include (1)
Group: 232.1.1.1
Source: {2.2.2.2}
Report
(224.0.0.22)
H3
Type: Include (1)
Group: 232.1.1.1
Source: {2.2.2.2}
Report
(224.0.0.22)
(224.0.0.1)
Query
Group: 0.0.0.0
Source: {}
•
Router sends periodic General Queries to All Hosts
•
•
General Query: Group=0, #Srcs=0
Member
Group: 232.1.1.1
Source: 2.2.2.2
All IGMP members respond
Hn
•
(Destination IP Address)
Reports can contain multiple Group State records
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25
IGMPv3 – Leaving Group “G” Source “S”
192.168.102.10
H1
192.168.102.11
1
H2
192.168.102.12
2
Type: Block Old (6)
Group: 232.1.1.1
Source: {2.2.2.2}
Report
(224.0.0.22)
H3
(232.1.1.1)
Query
Group: 232.1.1.1
Source: {2.2.2.2}
H2 leaves Group-Source
2. Sends “Block Old” Membership Report
3. Router sends Group-Source Query
3
1.
•
Hn
Group-Source Query: Group=G, #Srcs=N
Member
Group: 232.1.1.1
Source: 2.2.2.2
(Destination IP Address)
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26
IGMPv3 – Leaving Group “G” Source “S”
192.168.102.10
192.168.102.11
192.168.102.12
H1
H2
H3
Type: Include
Group: 232.1.1.1
Source: {2.2.2.2} 4
Report
(224.0.0.22)
5
H2 leaves Group-Source
Sends “Block Old” Membership Report
3. Router sends Group-Source Query
4. A remaining member host sends report
5. Group-Source flow remains active
1.
2.
Hn
Member
Group: 232.1.1.1
Source: 2.2.2.2
(Destination IP Address)
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27
IGMPv3 – Leaving Group “G” Source “S”
192.168.102.10
192.168.102.11
H1
H2
192.168.102.12
6
H3
Type: Block Old (6)
Group: 232.1.1.1
Source: {2.2.2.2}
Report
7
(224.0.0.22)
(232.1.1.1)
Query
8
Group: 232.1.1.1
Source: {2.2.2.2}
H3 leaves Group-Source
7. Sends “Block Old” Membership Report
8. Router sends Group-Source Query
6.
Hn
Member
Group: 232.1.1.1
Source: 2.2.2.2
(Destination IP Address)
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28
IGMPv3 – Leaving Group “G” Source “S”
192.168.102.10
192.168.102.11
192.168.102.12
H1
H2
H3
9
H3 leaves Group-Source
7. Sends Remove Membership Report
8. Router sends Group-Source specific query
9. State times out. Group-Source flow pruned.
6.
Hn
Member
Group: 232.1.1.1
Source: 2.2.2.2
(Destination IP Address)
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29
Unicast vs. Multicast Routing/Forwarding
Unicast Routing/Forwarding
•
Destination IP address directly indicates where to forward packet
•
Unicast Routing protocols build a table of destination/interface/next-hop triples
•
Unicast Forwarding is hop-by-hop simply based on these entries
•
Unicast routing table determines interface and next-hop router to forward packet
BRKIPM-1261
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30
Unicast vs. Multicast Routing/Forwarding
Multicast Routing & Forwarding
• Destination Group address doesn’t directly indicate where to forward packet.
•
•
Forwarding State must be created to build trees to describe forwarding path.
Multicast Routing is Backwards from Unicast Routing
•
Multicast Routing builds a tree backwards from the receivers to the source.
•
•
Concerned with “Where the packet will come from?”
More specifically, “What’s the route back to the Source?”
Trees are built via connection requests (Joins) “sent” toward the source.
• Joins follow the unicast routing table backwards toward the source.
• Joins create Multicast tree/forwarding state in the routers along the tree.
•
•
•
Trees are rebuilt dynamically in case of network topology changes.
Only when a tree is completely built from receiver backwards to the source can source
traffic flow down the tree to the receivers.
•
Say that over and over to yourself when working with Multicast!
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31
Unicast vs. Multicast Routing/Forwarding
Multicast Routing & Forwarding
All of this can easily lead to “thinking with your Unicast Lizard Brain!”
•
If you ever get confused by Multicast, just remember to . . .
“Stand on your head!”
•
BRKIPM-1261
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32
Source-Specific Multicast (SSM)
BRKIPM-1261
33
Source Specific Multicast (SSM) Concepts
•
Assumes one-to-many model
•
Most Internet multicast fits this model
• IP/TV also fits this model
•
Hosts responsible for source discovery
•
Typically via some out-of-band mechanism
•
•
Web page, Content Server, etc.
Hosts join a specific source within a group
•
Content identified by specific (S,G)
• Dissimilar content sources can use same group “G” without fear of interfering with each
other
•
Last-hop router sends (S,G) join toward source
•
Only specified (S,G) flow is delivered to host
BRKIPM-1261
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34
Multicast Tree Building
1.
Multicast packet’s source address is checked against the unicast routing table
2.
Determines interface & next-hop multicast router in the direction of the source
•
This is where the Joins are to be sent
This interface becomes the “Incoming” interface
3.
Often referred to as the “RPF” (Reverse Path Forwarding) interface
• A router forwards a multicast datagram only if received on the Incoming/RPF interface
•
•
A bit of History
The term “RPF” is actually a left-over from early Dense mode Multicast days
• Multicast traffic was flooded everywhere (i.e. no explicit Join signaling to build trees)
• Traffic was only accepted on the “RPF” interface to avoid loops
• We still tend to use the term to indicate the calculation of the Incoming interface.
•
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35
Multicast Routing & Forwarding
Traffic to
232.1.1.1
Source
2.2.2.2
Receiver
Multicast Traffic
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36
Multicast Routing & Forwarding
Traffic to
232.1.1.1
Source
2.2.2.2
IGMP “Join”
(2.2.2.2, 232.1.1.1)
Receiver
Forwarding State
Multicast Traffic
Mroute Entry
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37
Multicast Routing & Forwarding
Traffic to
232.1.1.1
Source
2.2.2.2
PIM Join
(2.2.2.2, 232.1.1.1)
Receiver
Forwarding State
Multicast Traffic
Mroute Entry
Mroute Entry
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38
Multicast Routing & Forwarding
Traffic to
232.1.1.1
PIM Join
(2.2.2.2, 232.1.1.1)
Source
2.2.2.2
Mroute Entry
Receiver
Forwarding State
Multicast Traffic
Mroute Entry
Mroute Entry
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39
Multicast Routing & Forwarding
Traffic to
232.1.1.1
Source
2.2.2.2
Mroute Entry
Receiver
Forwarding State
Multicast Traffic
Mroute Entry
Mroute Entry
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40
Multicast Routing & Forwarding
Traffic to
232.1.1.1
IGMP “Join”
(2.2.2.2, 232.1.1.1)
Receiver
Source
2.2.2.2
Mroute Entry
Mroute Entry
Receiver
Forwarding State
Multicast Traffic
Mroute Entry
Mroute Entry
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41
Multicast Routing & Forwarding
Traffic to
232.1.1.1
PIM Join
(2.2.2.2, 232.1.1.1)
Receiver
Source
2.2.2.2
Mroute Entry
Mroute Entry
Receiver
Forwarding State
Multicast Traffic
Mroute Entry
Mroute Entry
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42
Multicast Routing & Forwarding
Traffic to
232.1.1.1
Receiver
Source
2.2.2.2
Mroute Entry
Mroute Entry
Receiver
Forwarding State
Multicast Traffic
Mroute Entry
Mroute Entry
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43
Multicast Routing & Forwarding
Mroute Entry
Traffic to
232.1.1.1
show ip mroute 232.1.1.1
(2.2.2.2, 232.1.1.1), 3w1d/00:02:40, flags: s
Incoming interface: Ethernet 0/0, RPF nbr 207.109.83.33
Outgoing interface list:
Ethernet 0/1, Forward/Sparse, 3w1d/00:02:40
Ethernet 0/2, Forward/Sparse, 2w0d/00:02:33
Receiver
Source
2.2.2.2
Mroute Entry
Mroute Entry
Receiver
Forwarding State
Multicast Traffic
Mroute Entry
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44
Multicast Routing & Forwarding
Mroute Entry
Traffic to
232.1.1.1
show ip mroute 232.1.1.1
(2.2.2.2, 232.1.1.1), 3w1d/00:02:40, flags: s
Incoming interface: Ethernet 0/0, RPF nbr 207.109.83.33
Outgoing interface list:
Ethernet 1/0, Forward/Sparse, 3w1d/00:02:40
Ethernet 2/0, Forward/Sparse, 2w0d/00:02:33
Receiver
Source
2.2.2.2
Receiver
Forwarding State
Multicast Traffic
This type of Multicast has a special name: Source Specific Multicast (SSM)
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45
Multicast Tree Building
RPF Calculation
•
Based on source address
•
Best path to source found in unicast route table
SRC
10.1.1.1
A
•
Determines where to send join
•
Joins continue towards source to build multicast tree
•
Multicast data flows down tree
Join
C
B
D
Join
E0
E1
E
E2
Unicast Route Table
Network
Interface
10.1.0.0/24
E0
BRKIPM-1261
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46
Multicast Tree Building
RPF Calculation
•
Based on source address
•
Best path to source found in unicast route table
SRC
10.1.1.1
A
•
Determines where to send join
•
Joins continue towards source to build multicast tree
•
Multicast data flows down tree
Join
C
B
Join
D
E0
R2
E1
E
E2
R1
BRKIPM-1261
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47
Multicast Tree Building
RPF Calculation
•
What if we have equal-cost paths?
•
•
SRC
We can’t use both
Tie-breaker
•
10.1.1.1
A
Use highest next-hop IP address
B
C
D
1.1.1.1
E0
Unicast Route Table
Network
Intfc Nxt-Hop
10.1.0.0/24 E0 1.1.1.1
10.1.0.0/24 E1 1.1.2.1
BRKIPM-1261
E
1.1.2.1
Join
E1
F
E2
R1
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48
Multicast State
Multicast route entries are in (S,G) form.
rtr-a#show ip mroute 232.1.1.1
(2.2.2.2, 232.1.1.1), 3w1d/00:02:40, flags: s
Incoming interface: Ethernet 0/0, RPF nbr 207.109.83.33
Outgoing interface list:
Ethernet 1/0, Forward/Sparse, 3w1d/00:02:40
Ethernet 2/0, Forward/Sparse, 2w0d/00:02:33
Incoming interface points upstream
toward the root of the tree (i.e. Source)
OIL entries are refreshed by downstream
receivers roughly every 3 minutes or the
entry times out. [i.e. Soft State]
Outgoing interface list (OIL) is where receivers
have joined downstream and where packets
will be replicated and forwarded downstream.
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
49
Multicast State
rtr-a#show ip mroute 232.1.1.1
(2.2.2.2, 232.1.1.1), 3w1d/00:02:40, flags: s
Incoming interface: Ethernet 0/0, RPF nbr 207.109.83.33
Outgoing interface list:
Ethernet 1/0, Forward/Sparse, 3w1d/00:02:40
Ethernet 2/0, Forward/Sparse, 2w0d/00:02:33
rtr-b#show ip route 232.1.1.109
% Network not in table
Multicast Group addresses
are NEVER in the unicast
route table.
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
50
Multicast State
rtr-a#show ip mroute 232.1.1.1
(2.2.2.2, 232.1.1.1), 3w1d/00:02:40, flags: s
Incoming interface: Ethernet 0/0, RPF nbr 207.109.83.33
Outgoing interface list:
Ethernet 1/0, Forward/Sparse, 3w1d/00:02:40
Ethernet 2/0, Forward/Sparse, 2w0d/00:02:33
POP QUIZ QUESTION #1!!
How is the Incoming Interface and
RPF Neighbor determined?
ANSWER:
The best route to the Source IP Address
is looked up in the route table and the RPF
Neighbor is the next upstream PIM neighbor.
BRKIPM-1261
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51
Multicast State
rtr-a#show ip mroute 232.1.1.1
(2.2.2.2, 232.1.1.1), 3w1d/00:02:40, flags: s
Incoming interface: Ethernet 0/0, RPF nbr 207.109.83.33
Outgoing interface list:
Ethernet 1/0, Forward/Sparse, 3w1d/00:02:40
Ethernet 2/0, Forward/Sparse, 2w0d/00:02:33
POP QUIZ QUESTION #2!!
What causes interfaces to be added
to the Outgoing Interface List?
ANSWER:
IGMP “Joins” or PIM Joins that are
received on that interface.
BRKIPM-1261
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52
Basic SSM only Multicast Configuration
Assumes only 1:Many Multicast
•
Enable Multicast Routing on every router
ip multicast routing
•
Configure every interface for Multicast
•
IOS-XR – On by default
•
•
•
When ip multicast routing is configured
IOS – ip pim sparse mode
Configure SSM for all Multicast groups
ip pim ssm range 10
access-list 10 permit 224.0.0.0 15.255.255.255
•
Use DNS SSM-Mapping for non-IGMPv3 compatible apps on edge interfaces
ip igmp ssm-map enable
• Static config-based SSM Mapping is also possible
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
53
SSM Mapping – DNS Example
DNS Record Format:
3.2.1.232
PIM (S,G) join
PIM (S,G) join
IN A
172.23.20.70
Reverse DNS
lookup for
group G
DNS response:
Group G -> Source S
IGMPv2 join
Set Top
Box (STB)
BRKIPM-1261
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54
Multicast Routing & Forwarding
•
Key Point
•
If you ever get confused by Multicast . . .
. . . just remember to “Stand on your head”.
(Because Multicast is an Upside-down world where we are
interested in where the packet came from, not its destination
address.)
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
55
Multicast Fundamentals
Multicast Myth Busters
“Multicast is complicated, scary and hard
to understand!”
BRKIPM-1261
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56
Multicast Fundamentals
See there . . .
. . . that wasn’t so hard, was it?
BRKIPM-1261
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57
Multicast Fundamentals
But wait, my network has Many:Many
Multicast applications!
How do I support them?
BRKIPM-1261
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58
Bidirectional Multicast
i.e. Bidir PIM
BRKIPM-1261
59
Bidirectional (BiDir) PIM Concepts
Idea:
•
Use a common “Shared” Tree to connect all Sources and Receivers.
•
Root this “Shared” Tree at a point in the network called the Rendezvous Point
(RP)
•
Traffic flows up the tree from Sources to the RP and then down the tree to
Receivers
•
Data traveling from Source toward RP is moving UPSTREAM
• Data traveling from RP toward Receivers is moving DOWNSTREAM
BRKIPM-1261
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60
Bidirectional (BiDir) PIM Concepts
Implementation Details:
•
Designated Forwarders (DF)
•
One DF per link
•
•
•
•
BiDir (*,G) forwarding rules:
•
•
Router with best path to the RP is elected DF
Election mechanism insures all routers on link agree on who is DF
Prevents route loops from forming
DF is the only router that picks-up upstream traveling packets off the link to forward
towards the RP
This is like a constrained L3 Spanning-Tree for the Group
•
Constrained because it only “spans” to Sources and Receivers for the Group
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
61
How do hosts Join a Shared Tree
using IGMPv3?
BRKIPM-1261
62
IGMPv3 – Joining a Shared Tree for All Sources
192.168.102.10
192.168.102.11
H1
H2
192.168.102.12
Type: Exclude (2)
Group: 239.1.2.21
Source List: {}
Report
(224.0.0.22)
H3
Router#sh ip igmp groups 239.1.2.21 detail
Flags: L - Local, U - User, SG - Static Group, VG - Virtual Group,
SS - Static Source, VS - Virtual Source,
Ac - Group accounted towards access control limit
Interface: GigabitEthernet3/3
Group:
239.1.2.21
Flags:
Uptime:
00:00:22
Group mode: EXCLUDE (Expires: 00:02:49)
Last reporter:
192.168.102.11
Source list is empty
BRKIPM-1261
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63
Bidir Forwarding/Tree Building
RP
E0 (DF)
E0
E0
E
F
E1 (DF)
E0
A
E1 (DF)
E0
B
E1 (DF)
E0
E0
C
E1 (DF)
D
E1 (DF)
E1 (DF)
IGMP (*,G)
Join
Receiver 1
BRKIPM-1261
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64
Bidir Forwarding/Tree Building
RP
E0 (DF)
E0
E0
E
F
E1 (DF)
E0
A
E1 (DF)
E0
B
E1 (DF)
E0
E0
C
E1 (DF)
D
E1 (DF)
E1 (DF)
(*, 224.1.1.1), 00:00:04/00:00:00, RP 172.16.21.1, flags: BC
Bidir-Upstream: Ethernet0, RPF nbr 172.16.9.1
Outgoing interface list:
Ethernet0, Bidir-Upstream/Sparse-Dense, 00:00:04/00:00:00
Ethernet1, Forward/Sparse-Dense, 00:00:04/00:02:55
Receiver 1
Bidir State created in “D”
BRKIPM-1261
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65
Bidir Forwarding/Tree Building
RP
E0 (DF)
E0
E0
E
F
E1 (DF)
E0
A
E1 (DF)
E0
B
E1 (DF)
E0
E0
C
E1 (DF)
PIM (*,G)
Join
D
E1 (DF)
E1 (DF)
(*, 224.1.1.1), 00:00:04/00:00:00, RP 172.16.21.1, flags: BC
Bidir-Upstream: Ethernet0, RPF nbr 172.16.7.1
Outgoing interface list:
Ethernet0, Bidir-Upstream/Sparse-Dense, 00:00:04/00:00:00
Ethernet1, Forward/Sparse-Dense, 00:00:04/00:02:55
Receiver 1
Bidir State created in “F”
BRKIPM-1261
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66
Bidir Forwarding/Tree Building
RP
PIM (*,G)
Join
E0 (DF)
E0
E0
E
F
E1 (DF)
E0
A
E1 (DF)
E0
B
E1 (DF)
E0
E0
C
E1 (DF)
D
E1 (DF)
E1 (DF)
(*, 224.1.1.1), 00:32:20/00:02:59, RP 172.16.21.1, flags: B
Bidir-Upstream: Null, RPF nbr 0.0.0.0
Outgoing interface list:
Ethernet0, Forward/Sparse-Dense, 00:00:04/00:02:55
Receiver 1
Branch of Shared Tree is now built from RP down to Receiver 1
BRKIPM-1261
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67
Bidir Forwarding/Tree Building
RP
E0 (DF)
E0
E0
E
F
E1 (DF)
E0
A
E0
B
E1 (DF)
Source
E1 (DF)
E0
E0
C
E1 (DF)
D
E1 (DF)
E1 (DF)
(*, 224.1.1.1), 00:32:20/00:02:59, RP 172.16.21.1, flags: BP
Bidir-Upstream: Ethernet0, RPF nbr 172.16.7.1
Outgoing interface list:
Receiver 1
Ethernet0, Bidir-Upstream/Sparse-Dense, 00:32:20/00:00:00
Arriving Traffic from Source causes Router “A” to create (*, G) State
BRKIPM-1261
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68
Bidir Forwarding/Tree Building
RP
E0 (DF)
E0
E0
E
F
E1 (DF)
E0
A
E0
B
E1 (DF)
Source
E1 (DF)
E0
E0
C
E1 (DF)
D
E1 (DF)
E1 (DF)
(*, 224.1.1.1), 00:32:20/00:02:59, RP 172.16.21.1, flags: BP
Bidir-Upstream: Ethernet0, RPF nbr 172.16.7.1
Outgoing interface list:
Ethernet0, Bidir-Upstream/Sparse-Dense, 00:32:20/00:00:00
Receiver 1
Arriving Traffic Causes Router “E” to create (*, G) State
BRKIPM-1261
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69
Bidir Forwarding/Tree Building
RP
E0 (DF)
E0
E0
Bidir State in RP
E
E1 (DF)
E0
A
E0
B
E1 (DF)
(*, 224.1.1.1),F 00:32:20/00:02:59, RP 172.16.21.1, flags: B
E1 (DF)
Bidir-Upstream: Null, RPF nbr 0.0.0.0
Outgoing interface list:
E0
E0
Ethernet0,
Forward/Sparse-Dense,
00:00:04/00:02:55
C
E1 (DF)
D
E1 (DF)
E1 (DF)
Receiver 1
Source
RP already has (*, G) State
BRKIPM-1261
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70
Bidir Forwarding/Tree Building
RP
E0 (DF)
E0
E0
E
F
E1 (DF)
E0
A
E1 (DF)
E0
B
E1 (DF)
E0
E0
C
E1 (DF)
D
E1 (DF)
E1 (DF)
Receiver 1
Source
Traffic flows up the Shared Tree . . .
. . . and then back down the Shared Tree
BRKIPM-1261
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71
Basic Bidir only Multicast Configuration
•
Enable Multicast Routing on every router
ip multicast routing
•
Configure every interface for Multicast
•
IOS-XR – On by default
•
•
•
When ip multicast routing is configured
IOS – ip pim sparse mode
Enable Bidir Multicast Routing on every router
ip pim bidir enable
•
Configure address of Bidir RP for all Multicast groups
ip pim rp-address <ip-address> bidir
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
72
Bidir RP Redundancy using Phantom RP
Static route config option
Primary injecting RP
Secondary injecting RP
Phantom RP
1.1.1.1
ip multicast-routing
ip multicast-routing
interface Loopback0
ip address 11.0.0.1 255.255.255.255
ip pim sparse-mode
interface Loopback0
ip address 11.0.0.2 255.255.255.255
ip pim sparse-mode
router ospf 11
redistribute static subnets
router ospf 11
redistribute static subnets
ip route 1.1.1.1 255.255.255.255 Loopback0
ip route 1.1.1.0 255.255.255.254 Loopback0
ip pim bidir-enable
ip pim rp-address 1.1.1.1 bidir
ip pim bidir-enable
ip pim rp-address 1.1.1.1 bidir
BRKIPM-1261
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73
What Makes Multicast
Complicated?
BRKIPM-1261
74
Biggest Multicast Complicating Factor
Network-Based Source Discovery
•
Lazy One-to-Many Application Developers
•
•
“Let’s just let the Network do all the work to keep track of Sources.”
Uses old and outdated IGMPv2 methods to join (*,G) only.
•
Really!!!! IGMPv3 has been out for 10+ years!!
• Even Apple OS supports IGMPv3
•
•
Suffers from Capt. Midnight stream hijacking
Complicates Multicast Address management/allocation
•
•
Ad-Hoc Multicast Applications
•
•
•
Now you have to worry about what application uses what Multicast Address
No “good” way to know or predict who will become a source.
Sometimes you just have to support Network-Based Source Discovery
Requires complex Any-Source Multicast (ASM) & Rendezvous Point Engineering/Mgmt
•
Or maybe just BiDir Multicast?
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
75
Multicast Complicating Factor
Network-Based Source Discovery
•
Requires Any-Source Multicast (ASM)
•
•
•
•
•
•
Much, much more complicated than SSM or Bidir
Requires physical Rendezvous Point (RP) router(s) & RP Redundancy methods
Uses Shortest-Path Trees (ala SSM) to first deliver traffic to RP
Then uses a common “Shared Tree” rooted at RP to deliver all Multicast traffic
Routers w/directly connected receivers then learn about new sources via Shared Tree
Then join Shortest-Path Tree to all the sources.
. . . or maybe just use Bidir Multicast (Bidir)
•
A bit more complicated than Source Specific Multicast but easier than ASM.
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
76
Any-Source Multicast
i.e. ASM PIM
BRKIPM-1261
77
PIM-SM Shared Tree Join
RP
(*, G) State Created Only
Along the Shared Tree
(*, G) Join
Shared Tree
Receiver
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
78
PIM-SM Sender Registration
RP
Source
Traffic Flow
Shared Tree
Source Tree
(S, G) Register
(S, G) Join
(S, G) State Created Only
Along the Source Tree
(unicast)
Receiver
BRKIPM-1261
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79
PIM-SM Sender Registration
RP
Source
Traffic Flow
Shared Tree
Source Tree
(S, G) Register
(S, G) Register-Stop
(S, G) Traffic Begins Arriving at
the RP via the Source Tree
(unicast)
(unicast)
Receiver
BRKIPM-1261
RP Sends a Register-Stop Back
to the First-Hop Router to Stop
the Register Process
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
80
PIM-SM Sender Registration
RP
Source
Source Traffic Flows Natively
Along SPT to RP
Traffic Flow
Shared Tree
Source Tree
From RP, Traffic Flows Down
the Shared Tree to Receivers
Receiver
BRKIPM-1261
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81
PIM-SM SPT Switchover
RP
Source
Traffic Flow
Shared Tree
Source Tree
(S, G) Join
Last-Hop Router Joins the
Source Tree
Receiver
BRKIPM-1261
Additional (S, G) State Is
Created Along New Part of the
Source Tree
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
82
PIM-SM SPT Switchover
RP
Source
Traffic Flow
Shared Tree
Source Tree
(S, G)RP-bit Prune
Receiver
BRKIPM-1261
Traffic Begins Flowing
Down the New Branch of
the Source Tree
Additional (S, G) State Is Created
Along the Shared Tree to Prune Off
(S, G) Traffic
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
83
PIM-SM SPT Switchover
RP
Source
(S, G) Traffic Flow Is Now Pruned
Off of the Shared Tree and Is
Flowing to the Receiver via the
Source Tree
Traffic Flow
Shared Tree
Source Tree
Receiver
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
84
PIM-SM SPT Switchover
RP
Source
Traffic Flow
Shared Tree
Source Tree
(S, G) Prune
(S, G) Traffic Flow Is No
Longer Needed by the RP so It
Prunes the Flow of (S, G)
Traffic
Receiver
BRKIPM-1261
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85
PIM-SM SPT Switchover
RP
Source
(S, G) Traffic Flow Is Now Only
Flowing to the Receiver via a
Single Branch of the Source
Tree
Traffic Flow
Shared Tree
Source Tree
Receiver
BRKIPM-1261
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86
Basic ASM-Only Multicast Configuration
•
Enable Multicast Routing on every router
ip multicast routing
•
Configure every interface for Multicast
•
IOS-XR – On by default
•
•
•
When ip multicast routing is configured
IOS – ip pim sparse mode
Configure address of ASM RP for all Multicast groups
ip pim rp-address <ip-address>
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
87
The default behavior of PIM-SM (ASM) is
that routers with directly connected
members will join the shortest path tree
as soon as they detect a new multicast
source.”
– PIM Frequently Forgotten Fact
BRKIPM-1261
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88
But what about PIM Dense Mode??
“Fuggidaboudit!”
“Fuggidaboudit!”
Click to edit
Source:
“Thesource
Wiseguys’s Guide to IP Multicast”, ©2005, T. Soprano
It does “Flood & Prune” without any Joins!
It can meltdown your network and blackhole your traffic!
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
89
Inter-domain IP Multicast
BRKIPM-1261
90
MP-BGP Overview
MP-BGP: Multiprotocol BGP
•
Originally defined in RFC 2858 (extensions to BGP)
•
Can carry different types of routes
•
Unicast
• Multicast
•
Both routes carried in same BGP session
•
Does not propagate multicast state info
•
•
That’s PIM’s job
Same path selection and validation rules
•
AS-Path, LocalPref, MED…
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
91
MP-BGP Overview
•
Separate BGP tables maintained
•
Unicast prefixes for Unicast forwarding
• Unicast prefixes for Multicast RPF calculation
•
AFI = 1, Sub-AFI = 1
•
Contains Unicast prefixes for Unicast forwarding
• Populated with BGP Unicast NLRI
•
AFI = 1, Sub-AFI = 2
•
Contains Unicast prefixes for Multicast RPF calculation
• Populated with BGP Multicast NLRI
BRKIPM-1261
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92
MBGP Overview
MBGP Allows Divergent Paths and Policies
•
Same IP address holds dual significance
•
Unicast Routing information
• Multicast RPF information
•
For same IPv4 address two different NLRI with different next-hops
•
Can therefore support both congruent and incongruent topologies
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
93
Inter-domain Multicast – Simple. Use SSM!
Domain E
MP-BGP Peering
Domain C
Receiver
Receiver Learns
S and G Out of
Band, i.e.,
Webpage
Domain B
Domain D
Source in 232/8
Source “S”
Domain A
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
94
Inter-domain Multicast – Simple. Use SSM!
Domain E
MP-BGP Peering
Multicast Traffic
Domain C
Receiver
Data flows natively
along the interdomain
source tree
Domain B
Domain D
Source in 232/8
Source “S”
Domain A
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
95
Inter-domain Bidir? – Not really
Historical Issues:
•
Deciding who (what SP/ASN) owns RP was problematic.
•
Some SP’s wanted their own RP.
•
Other SP’s didn’t want RP’s in their network.
•
No consensus was ever reached.
•
Inter-domain Bidir never got off the ground.
•
Don’t hold your breath looking for Inter-domain Bidir support from Vendors/SPs
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
96
Inter-domain ASM
Issues
•
Global Group Address Allocation/Management
•
With ASM we have to make sure that we use unique Groups
•
•
Otherwise we start mixing up the Multicast flows
Solution(?): GLOP Addressing
•
•
•
233.0.0.0–233.255.255.255
Put your ASN in the middle two Octets
Provides /24 group prefix per ASN
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
97
Inter-domain ASM
Issues
•
How do we do Inter-domain Source Discovery?
•
Can we all agree on what domain “owns” the RP?
•
And for which Global Multicast Group??
• GLOP Addressing?
•
Why not have RP’s in each domain “share” Source information?
•
Solution: Multicast Source Discovery Protocol (MSDP)
BRKIPM-1261
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98
MSDP – Multicast Source Discovery Protocol
•
RFC 3618 - Multicast Source Discovery Protocol (MSDP)
•
PIM ASM only solution
•
RPs knows about all Sources in their domain
•
•
•
Sources cause a “PIM Register” to the RP
RP tells RPs in other domains of it’s Sources
• Uses “MSDP SA” (Source Active) messages
RPs know about existence of Receivers in their domain
•
•
Receivers cause a “(*, G) Join” to the RP
RP can join the Source tree in the peer domain
• Uses normal PIM “(S, G) Join”
BRKIPM-1261
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99
MSDP Overview
MSDP Example
Domain E
RP
MSDP Peers
Join (*, 233.3.2.1)
Receiver
Domain C
RP
Domain B
RP
RP
Domain D
ASN770
GLOP: 233.3.2.0/24
RP
Domain A
BRKIPM-1261
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100
MSDP Overview
MSDP Example
Domain E
RP
MSDP Peers
Source Active
Messages
SA
SA
Receiver
Domain C
RP
SA
SA
Domain B
SA
RP
SA
SA
SA Message
8.1.1.1, 233.3.2.1
ASN770
RP
Source
RP
SA Message
GLOP: 233.3.2.0/24
8.1.1.1, 233.3.2.1
Domain D
Domain A
Register
8.1.1.1, 233.3.2.1
BRKIPM-1261
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101
MSDP Overview
MSDP Example
Domain E
RP
MSDP Peers
Receiver
Domain C
RP
Domain B
RP
RP
Domain D
ASN770
GLOP: 233.3.2.0/24
RP
Source
Domain A
BRKIPM-1261
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102
MSDP Overview
MSDP Example
Domain E
RP
MSDP Peers
Multicast Traffic
Receiver
Domain C
RP
Domain B
RP
RP
Domain D
ASN770
GLOP: 233.3.2.0/24
RP
Source
Domain A
BRKIPM-1261
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103
MSDP Overview
MSDP Example
Domain E
RP
MSDP Peers
Multicast Traffic
Receiver
Domain C
RP
Domain B
RP
RP
Domain D
ASN770
GLOP: 233.3.2.0/24
RP
Source
Domain A
BRKIPM-1261
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104
MSDP Overview
MSDP Example
Domain E
RP
MSDP Peers
Multicast Traffic
Receiver
Domain C
RP
Domain B
RP
RP
Domain D
ASN770
GLOP: 233.3.2.0/24
RP
Source
Domain A
BRKIPM-1261
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105
ASM Redundant RP Choices
BRKIPM-1261
106
C-RP
1.1.1.1
C
Announce
B
Announce
Announce
A
MA
Announce
Announce
MA
D
Announce
Announce
Auto-RP – From 10,000 Feet
Announce
C-RP
2.2.2.2
RP-Announcements Multicast to the
Cisco Announce (224.0.1.39) Group
Announce
BRKIPM-1261
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107
Auto-RP – From 10,000 Feet
MA
A
C-RP
1.1.1.1
MA
B
C
D
C-RP
2.2.2.2
RP-Discoveries Multicast to the
Cisco Discovery (224.0.1.40) Group
Discovery
BRKIPM-1261
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108
Auto-RP Configuration
Global Configuration Commands
•
Candidate RPs
ip pim send-rp-announce <interface> scope <ttl> [group-list <acl>] [interval <rp-announce-interval>] [ bidir ]
•
•
Primary address of <interface> is used as RP-address
• If <interface> goes down, C-RP messages are not sent (use Loopback)
Mapping Agents
ip pim send-rp-discovery [<interface>] scope <ttl> [interval <interval>]
•
•
Configure <interface> as Loopback Interface.
• Same reason recommended for C-RP
Auto-RP Listeners
ip pim autorp listener
•
•
Enable on all routers (even MA and C-RPs)
Enables all routers to listen to (and forward) RP-Announce and RP-Discover messages
• Allowing us to move away from old IOS sparse-dense operation.
BRKIPM-1261
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109
BSR – From 10,000 Feet
BSR Election Process
G
C-BSR
C-BSR
D
C-BSR
A
F
B
BSR Msgs
C
E
BSR Msgs Flooded Hop-by-Hop
BRKIPM-1261
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110
BSR – From 10,000 Feet
Highest Priority C-BSR
Is Elected as BSR
G
BSR
D
A
F
B
C
E
BRKIPM-1261
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111
BSR – From 10,000 Feet
G
BSR
D
C-RP
A
F
B
C
C-RP
E
BRKIPM-1261
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112
BSR – From 10,000 Feet
G
BSR
D
C-RP
A
F
B
BSR Msgs
C
C-RP
E
BSR Msgs Containing RP-SET
Flooded Hop-by-Hop
BRKIPM-1261
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113
BSR Configuration
Global Configuration Commands
•
Candidate-BSR (C-BSR)
ip pim bsr-candidate <interface> <hash-length> <priority> [accept-rp-candidate <acl>]
•
BSR election:
•
•
•
•
C-BSR with highest <priority> becomes BSR
Tie-breaker: Highest-IP-Address
Preemption by better C-BSR at any time
Candidate RP (C-RP)
ip pim rp-candidate <interface> [group-list <acl> | bidir | interval <rp-announce-interval> | priority <priority>]
•
All parameters as in AutoRP C-RP – except <priority>
BRKIPM-1261
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114
Anycast-RP w/MSDP: Intra-domain use of MSDP
•
Anycast-RP w/MSDP
•
•
Redundant RP technique for ASM which uses MSDP for RP synchronization
Uses single defined RP address
•
Two or more routers have same RP address
•
•
•
First/Last hop Routers Join/Register with closest RP
•
•
•
RP address defined as a loopback interface
Loopback address advertised as a host route
Closest RP determined from the unicast routing table
Because RP is statically defined
MSDP session(s) run between all RPs
•
Informs RPs of Sources in other parts of network
• RPs join SPT to active Sources as necessary
BRKIPM-1261
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115
Anycast RP w/MSDP – Overview
Src
RP1
RP2
X
MSDP
A
10.1.1.1
Rec
Src
SA
B
10.1.1.1
SA
Rec
Rec
BRKIPM-1261
Rec
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116
Anycast RP w/MSDP – Overview
Src
Src
RP2
A
10.1.1.1
B
10.1.1.1
X
RP1
Rec
Rec
Rec
BRKIPM-1261
Rec
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117
Anycast RP w/MSDP – Basic Configuration
Src
RP1
A
10.1.1.1
Src
MSDP
(Established via TCP)
RP2
B
10.1.1.1
interface Loopback1
description -> anycast RP
ip address 10.1.1.1 255.255.255.255
ip pim sparse-mode
interface Loopback1
description -> anycast RP
ip address 10.1.1.1 255.255.255.255
ip pim sparse-dense-mode
interface Loopback2
ip address 10.10.10.1 255.255.255.255
interface Loopback2
ip address 10.10.10.2 255.255.255.255
ip msdp peer 10.10.10.2 connect-source Loopback10
ip msdp originator-id Loopback2
ip msdp peer 10.10.10.1 connect-source Loopback20
ip msdp originator-id Loopback2
ip pim rp-address 10.1.1.1
ip pim rp-address 10.1.1.1
Rec
Rec
Rec
BRKIPM-1261
Rec
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118
Anycast-RP w/PIM only
Goal: Anycast RP without using another protocol i.e. MSDP
•
RFC4610 – Anycast-RP w/PIM only
•
•
Redundant RP technique for ASM which uses PIM Registers for RP synchronization
Uses single defined RP address
•
Two or more routers have same RP address
•
•
•
First/Last hop Routers Join/Register with closest RP
•
•
•
RP address defined as a loopback interface
Loopback address advertised as a host route
Closest RP determined from the unicast routing table
Because RP is statically defined
PIM Register messages exchanged between all RPs
•
Informs RPs of Sources in other parts of network
• RPs join SPT to active Sources as necessary
BRKIPM-1261
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119
Anycast RP w/PIM Registers – Overview
Src
RP1
A
10.1.1.1
Rec
RP2
PIM Anycast RP Neighbors
PIM Register
PIM Register Stop
Rec
Rec
BRKIPM-1261
B
10.1.1.1
Rec
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120
Anycast RP w/PIM Registers – Overview
Src
X
RP1
RP2
PIM Anycast RP Neighbors
A
10.1.1.1
Rec
Src
PIM Register Stop
B
10.1.1.1
PIM Register
Rec
Rec
BRKIPM-1261
Rec
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121
Anycast RP w/PIM Registers – Overview
Src
Src
RP2
A
10.1.1.1
B
10.1.1.1
X
RP1
Rec
Rec
Rec
BRKIPM-1261
Rec
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122
Anycast RP w/PIM Registers – Basic Configuration
RP1
PIM Anycast RP Neighbors
A
10.1.1.1
RP2
B
10.1.1.1
interface Loopback1
description -> anycast RP
ip address 10.1.1.1 255.255.255.255
ip pim sparse-mode
interface Loopback1
description -> anycast RP
ip address 10.1.1.1 255.255.255.255
ip pim sparse-mode
interface Loopback2
ip address 10.10.10.1 255.255.255.255
interface Loopback2
ip address 10.10.10.2 255.255.255.255
ip pim anycast-rp 10.1.1.1 10.10.10.1
ip pim anycast-rp 10.1.1.1 10.10.10.2
ip pim anycast-rp 10.1.1.1 10.10.10.1
ip pim anycast-rp 10.1.1.1 10.10.10.2
ip pim rp-address 10.1.1.1
ip pim rp-address 10.1.1.1
BRKIPM-1261
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123
Multicast at Layer 2
BRKIPM-1261
124
L2 Multicast Frame Switching
Problem: Layer 2 Flooding of Multicast Frames
•
Typical L2 switches treat multicast traffic as unknown or
broadcast and must “flood” the frame to every port
•
Static entries can sometimes be set to specify which ports
should receive which group(s) of multicast traffic
•
Dynamic configuration of these entries would cut down on
user administration
BRKIPM-1261
PIM
Multicast M
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125
IGMP Snooping
•
L2 switches now “listen to” and intercept IGMP & PIM packets
•
Builds “multicast mac table”. Prevents flooding (like unicast)
•
Mrouter Ports: Ports connected to a PIM Router
•
•
Dynamically learned upon hearing IGMP Queries or PIM Hellos
Forward IGMP joins, leaves & mcast data to this port towards PIM router
PIM
Switch# show ip igmp snooping mrouter
Type: S - Static, D – Dynamic
Vlan
143
Router-port
Eth8/11
Type
D
Uptime
4w1d
Expires
00:04:59
e8/11
Po1
BRKIPM-1261
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126
IGMP Snooping
•
L2 switches now “listen to” and intercept IGMP & PIM packets
•
Builds “multicast mac table”. Prevents flooding (like unicast)
•
Mrouter Ports: Ports connected to a PIM Router
•
•
Dynamically learned upon hearing IGMP Queries or PIM Hellos
Forward IGMP joins, leaves & mcast data to this port towards PIM router
PIM
•
Member Ports: Ports that have received an IGMP join
• Vlan: Vlan in which the above Member Port belongs
• Multicast Group: Group the member port has joined.
Switch# show ip igmp snooping groups
Type: S - Static, D - Dynamic, R - Router port
Vlan Group Address
Ver Type Port list
143
225.131.38.2
v2
D
Po1
BRKIPM-1261
e8/11
Po1
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127
Multicast over MPLS with mLDP
The 60,000’ View
BRKIPM-1261
128
Multipoint Label Distribution Protocol – mLDP
Why mLDP?
• Customers running MPLS in their network want to run Multicast natively over
MPLS
•
MPLS forwarding plane is shared between unicast and multicast
•
•
i.e. unicast MPLS features are applied to multicast
Separation of data plane and control plane has advantages
BRKIPM-1261
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129
Multipoint Label Distribution Protocol – mLDP
Terminology
• P2MP - Point to Multi-point
•
•
Like a PIM SSM tree
MP2MP – Multi-Point to Multi-Point
•
Like a PIM Bidir tree
•
MP LSP – Multi-Point LSP, either P2MP or MP2MP
•
Label Mapping
•
•
Like a PIM Join
Label Withdraw
•
Like a PIM Prune
BRKIPM-1261
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130
Multipoint Label Distribution Protocol – mLDP
Why mLDP?
•
Simplification compared to PIM
•
•
•
•
•
•
•
No shared tree / source tree switchover
No (S,G,R) prune’s
No DR election
No PIM registers
No Asserts
No Periodic messaging
No Auto-RP/BSR
BRKIPM-1261
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131
Multipoint Label Distribution Protocol – mLDP
Extensions to LDP
•
mLDP is an extension to the IETF LDP RFC 3036.
•
Procedures are documented in IETF RFC 6388
•
Joined effort by multiple vendors and customers.
•
mLDP reuses LDP protocol packets and neighbor adjacencies.
•
mLDP is a client of the LDP infrastructure.
•
mLDP allows the creation of P2MP and MP2MP LSPs
•
We refer to these as Multipoint LSPs (MP LSPs).
BRKIPM-1261
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132
BIER –
Bit-Indexed Explicit Replication
BRKIPM-1261
133
BIER history
•
A team was formed to investigate solutions for multicast in the context of
Segment Routing.
•
Encoding a Sourced routed Multicast tree path using MPLS labels is difficult.
•
The packet header would get very large, and its very hard to parse such header.
BRKIPM-1261
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134
The BIER Epiphany
•
Only encode the end-receivers in the packet header.
•
•
Assign end-receivers a Bit Position from a Bit String.
•
•
Using some sort of encapsulation.
Create a Bit Forwarding Table on all BIER nodes to allow multicast packet
forwarding using the Bit String in the packet.
•
•
The smallest identifier possible.
Encode the Bit String in the packet header.
•
•
Not the intermediate nodes.
Derived from the RIB, SPF based.
We call it, Bit Indexed Explicit Replication (BIER).
BRKIPM-1261
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135
BIER – Basic Idea
A/32
B/32
BIER Domain
D/32
6
5
4
3
2
1
BitString/BFR-ID
C/32
E/32
F/32
1. Assign a unique Bit Position/BFR-ID1 from a BitString to each BFER2 in the domain.
1Bit-Position
2BFER
= BIER Forwarding Router-ID
= Bit-Forwarding Egress Router
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
136
BIER – Basic Idea
A/32
B/32
LSA
6 - A/32
LSA
5 – B/32
LSA
4 – C/32
BIER Domain
LSA
3 – E/32
LSA
1 – E/32
D/32
LSA
2 – D/32
6
5
4
3
2
1
BitString/BFR-ID
C/32
E/32
F/32
1. Assign a unique Bit Position/BFR-ID1 from a BitString to each BFER2 in the domain.
2. BFERs flood their BFR-Id/BFR Prefix to the Domain using the IGP (OSPF, ISIS)
1Bit-Position
2BFER
= BIER Forwarding Router-ID
= Bit-Forwarding Egress Router
BRKIPM-1261
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137
BIER – Basic Idea
A/32
B/32
BitMask
Nbr
0011
A
0100
B
1000
C
D/32
C/32
E/32
F/32
3. Each router in the BIER Domain builds Bit-Mask to BFR Prefix mapping table
1Bit-Position
2BFER
= BIER Forwarding Router-ID
= Bit-Forwarding Egress Router
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
138
BIER Bit-Mask Forwarding Table
BIER Bit-Mask Forwarding Table is based on shortest path to each BFR-ID
BM
Nbr
0111
B
BM
Nbr
BM
Nbr
0011
C
0001
D
0100
E
0010
F
D
BFR-ID 1
BS:0001
A
C
B
F
E
BM
0011
Nbr
C
BFR-ID 3
BS:0100
BFR-ID 2
BS:0010
B
BRKIPM-1261
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139
Forwarding Packets
BM
Nbr
0111
B
AND
BM
Nbr
BM
Nbr
0011
C
0001
D
0100
E
0010
F
D
BFR-ID 1
BS:0001
0001
A
C
B
Suppose A leans about D’s interest,
(via BGP, SDN, STATIC, etc…)
F
E
in the blue multicast flow.
BM
0011
Nbr
C
BFR-ID 3
BS:0100
BFR-ID 2
BS:0010
B
BRKIPM-1261
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140
Forwarding Packets
BM
Nbr
0111
B
BM
&0111
AND
Nbr
BM
Nbr
0011
C
0001
D
0100
E
0010
F
BFR-ID 1
BS:0001
0001
0001
A
C
B
• Result from the bitwise AND (&) between
the Bit Mask in the packet and the
Forwarding table is copied in the packet for
each neighbor.
• This is the key mechanism to prevent
duplication.
D
F
E
BM
0011
Nbr
C
BFR-ID 3
BS:0100
BFR-ID 2
BS:0010
B
BRKIPM-1261
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141
Forwarding Packets
BM
Nbr
0111
B
AND
BM
&0111
Nbr
0011
AND
C
0100
A
&0011
AND
E
0001
0001
BM
0001
D
0010
F
&0001
D
BFR-ID 1
BS:0001
0001
C
B
• Result from the bitwise AND (&) between
the Bit Mask in the packet and the
Forwarding table is copied in the packet for
each neighbor.
• This is the key mechanism to prevent
duplication.
Nbr
F
E
BM
0011
Nbr
C
BFR-ID 3
BS:0100
BFR-ID 2
BS:0010
B
BRKIPM-1261
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142
Forwarding Packets
BM
Nbr
0111
B
AND
BM
Nbr
BM
Nbr
0011
C
0001
D
0100
E
0010
F
D
BFR-ID 1
BS:0001
0111
A
C
B
Suppose A leans about D, E and F’s interest,
(via BGP, SDN, STATIC, etc…)
F
E
in the blue multicast flow.
BM
0011
Nbr
C
BFR-ID 3
BS:0100
BFR-ID 2
BS:0010
B
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
143
Forwarding Packets
Nbr
0111
B
AND
Nbr
&0111
0011
AND
C
0100
E
Nbr
&0011
&0100
0111
0111
A
AND
0001
D
&0001
0010
F
&0010
D
BFR-ID 1
BS:0001
0011
C
B
• Result from the bitwise AND (&) between
the Bit Mask in the packet and the
Forwarding table is copied in the packet for
each neighbor.
F
E
• This is the key mechanism to prevent
duplication.
BM
0011
AND
Nbr
C
BFR-ID 3
BS:0100
BFR-ID 2
BS:0010
B
BRKIPM-1261
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144
Failure to reset bits when Forwarding Packets
Nbr
0111
B
AND
Nbr
&0111
0011
AND
C
0100
E
Nbr
&0011
&0100
0111
A
0001
D
&0001
0010
F
&0010
D
BFR-ID 1
BS:0001
0111
C
B
0111
0111
AND
Duplicate Packets!!
F
E
Nbr
0011
AND
C
BFR-ID 3
BS:0100
BFR-ID 2
BS:0010
B
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
145
IPv6 Multicast
BRKIPM-1261
146
IPv4 vs. IPv6 Multicast
IP Service
IPv4 Solution
IPv6 Solution
Address Range
32-Bit, Class D
128-Bit (112-Bit Group)
Routing
Protocol-Independent
Protocol-Independent
All IGPs and GBP4+
All IGPs and BGP4+
with v6 Mcast SAFI
Forwarding
PIM-DM, PIM-SM:
ASM, SSM, BiDir
PIM-SM: ASM, SSM, BiDir
Group Management
IGMPv1, v2, v3
MLDv1, v2
Domain Control
Boundary/Border
Scope Identifier
Interdomain Source Discovery
MSDP Across Independent PIM
Domains
Single RP Within Globally Shared
Domains
BRKIPM-1261
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147
IPv6 Multicast Addresses
per RFC 4291
128 bits
8
FF
4
4
Flags Scope
1111 1111
F
8 bits
F
Group-ID
Flags
R P T Scope
Flags =
8 bits
Scope =
T or Lifetime, 0 if Permanent, 1 if Temporary
P for Unicast-based Assignments
R for Embedded RP
Others Are Undefined and Must Be Zero
1 = interface-local
2 = link
4 = admin-local
5 = site
8 = organization
E = global
0, 3, F = reserved
BRKIPM-1261
Note: Other scopes (6, 7, 9-D)
are unassigned but can be
used
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148
IPv6 Layer 2 Multicast Addressing Mapping
RFC 2464
IPv6 Multicast Address
112 Bits
8
FF
4
4
Flags Scope
80
High-Order
32
Low-Order
80 Bits Lost
•
Similar to IPv4: 5 bits are lost
•
•
More than 1 multicast address (in fact 2^80) will map to the
same MAC address.
•
•
(28 significant L3 multicast bits are mapped into 23 L2 MAC bits)
33-33-xx-xx-xx-xx
48 Bits
Ethernet MAC Address
For example: FF02::1  33-33-00-00-00-01
FF3E::1  33-33-00-00-00-01
Pick multicast group addresses that give distinct multicast MAC addresses
BRKIPM-1261
© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public
149
Unicast-based Multicast addresses
RFC 3306
8
FF
4
4
Flags Scope
8
Rsvd
8
Plen
64
Network-Prefix
32
Group-ID
• RFC 3306 – Unicast-based Multicast Addresses
– Similar to IPv4 GLOP Addressing (233/8 + ASN = 256 group addresses)
– Solves IPv6 global address allocation problem.
– Flags = 00PT
P = 1, T = 1
=>
Unicast-based Multicast address
– Example
Content provider’s unicast prefix
1234:5678:9abc::/48
Multicast address
FF3E:0030:1234:5678:9abc::1 (hex “30” is 48 bits)
BRKIPM-1261
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150
IPv6 Multicast Tree Building & Forwarding
•
PIM-Sparse Mode (PIM-SM)
•
•
RFC4601
PIM Source Specific Mode (SSM)
•
RFC3569 SSM overview (v6 SSM needs MLDv2)
• Unicast, prefix-based multicast addresses ff30::/12
• SSM range is ff3X::/96
•
PIM Bi-Directional Mode (BiDir)
•
RFC5015 – Bidirectional PIM (BIDIR-PIM)
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RP Mapping Mechanisms for IPv6
•
Static RP assignment
•
BSR
•
Embedded RP
•
No Auto-RP!
•
•
No current plans for Auto-RP at Cisco or IETF
No Anycast RP w/MSDP!
•
Because MSDP is not supported in IPv6
• No current plans for IPv6 MSDP at Cisco or IETF
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Embedded RP Addressing
Multicast Address with Embedded RP address – RFC3956
8
FF
•
4
4
4
4
Flags Scope Rsvd RPadr
8
Plen
64
Network-Prefix
32
Group-ID
Proposed new multicast address type
•
Uses unicast-based multicast addresses (RFC 3306)
•
RP address is embedded in multicast address
•
Flag bits = 0RPT
•
R = 1, P = 1, T = 1  Embedded RP address
•
Network-Prefix::RPadr = RP address
•
For each unicast prefix you own, you now also own:
•
16 RPs for each of the 16 multicast scopes (256 total) with 2^32 multicast groups assigned to each
RP (2^40 total)
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Embedded RP Addressing – Example
Multicast Address with Embedded RP address
8
FF
4
4
4
Flags Scope Rsvd
4
8
RPadr Plen
64
Network-Prefix
32
Group-ID
FF76:0130:1234:5678:9abc::4321
1234:5678:9abc::1
Resulting RP address
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Multicast Listener Discover—MLD
•
MLD is equivalent to IGMP in IPv4
•
MLD messages are transported over ICMPv6
•
Version number confusion
•
MLDv1 corresponds to IGMPv2
•
•
MLDv2 corresponds to IGMPv3, needed for SSM
•
•
RFC 2710
RFC 3810
MLD snooping
•
RFC4541 – Considerations for IGMP & MLD Snooping Switches
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Conclusion
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156
Now You Know…
•
Multicast Fundamentals
•
Source-Specific Multicast (SSM)
•
Bidirectional Multicast (Bidir)
•
Any-Source Multicast (ASM)
•
ASM Redundant RP Choices
•
Multicast at Layer 2
•
Multicast over MPLS – mLDP
•
Bit-Indexed Explicit Replication – BIER
•
Inter-domain IP Multicast
•
IPv6 Multicast
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