connecting to the ip multicast world

1

Connecting to the IP Connecting to the IP Multicast WorldMulticast World

Connecting to the IP Connecting to the IP Multicast WorldMulticast World

David MitchellDavid Mitchell

NCNE, NLANR, NCAR, and the NCNE, NLANR, NCAR, and the Pittsburgh Supercomputing Pittsburgh Supercomputing

CenterCenter

[email protected]@ncne.org

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AgendaAgenda

• What Is Multicast

• Multicast Protocols

• Multicast Configurations

• Troubleshooting

• Futures

• Useful Links

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What Is MulticastWhat Is Multicast

• Unicast is one to one– traffic is sent from a single source to a single

destination

• Multicast is one to many– traffic is sent from a single source to a “group”

address

4

Server

Router

Unicast

Server

Router

Multicast

Unicast vs. MulticastUnicast vs. Multicast

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Why MulticastWhy Multicast

• More efficient method of sending the same data to lots of hosts– Distributing a video stream to multiple viewers

• Allows unique distributed protocols– clients can announce services or perform queries

in a distributed fashion ala Appletalk’s “Chooser”

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Multicast Disadvantages

• Best Effort DeliveryBest 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.

• No Congestion AvoidanceNo 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.

• DuplicatesDuplicates: 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 DeliveryOut of Order Delivery : Some protocol mechanisms may also result in out of order delivery of packets.

Multicast Is UDP Based!!!

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AgendaAgenda




• Troubleshooting

• Futures

• Useful Links

8

Multicast ProtocolsMulticast Protocols

• Multicast Addressing Basics

• IGMP

• PIM

• MSDP

• MBGP

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• IP Multicast Group Addresses– 224.0.0.0–239.255.255.255– Class “D” Address Space

• High order bits of 1st Octet = “1110”

• Reserved Link-local Addresses– 224.0.0.0–224.0.0.255– Transmitted with TTL = 1– Examples:

• 224.0.0.1 All systems on this subnet• 224.0.0.2 All routers on this subnet• 224.0.0.4 DVMRP routers• 224.0.0.5 OSPF routers• 224.0.0.13 PIMv2 Routers

Multicast Addressing Multicast Addressing

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• 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

• Used to limit “scope” of multicast traffic

• Same addresses may be in use at different locations for different multicast sessions

– Examples• Site-local scope: 239.253.0.0/16

• Organization-local scope: 239.192.0.0/14


11

32 Bits

28 Bits

25 Bits 23 Bits

48 Bits

01-00-5e-7f-00-0101-00-5e-7f-00-01

1110

5 BitsLost

Multicast AddressingMulticast Addressing

IP Multicast MAC Address Mapping(FDDI and Ethernet)

239.255.0.1239.255.0.1

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224.1.1.1224.129.1.1225.1.1.1225.129.1.1 . . .238.1.1.1238.129.1.1239.1.1.1239.129.1.1

0x0100.5E01.0101

1 - Multicast MAC Address(FDDI and Ethernet)

32 - IP Multicast Addresses

Multicast AddressingMulticast Addressing

Be Aware of the 32:1 Address OverlapBe Aware of the 32:1 Address Overlap

IP Multicast MAC Address Mapping(FDDI & Ethernet)

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• Dynamic Group Address Assignment– Historically accomplished using SDR application

• Sessions/groups announced over well-known multicast groups

• Address collisions detected and resolved at session creation time

• Has problems scaling

– Future dynamic techniques under consideration• Multicast Address Set-Claim (MASC)

– Hierarchical, dynamic address allocation scheme– Extremely complex garbage-collection problem. – Long ways off

• MADCAP– Similar to DHCP– Need application and host stack support

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• Static Group Address Assignment (new)– Temporary method to meet immediate needs

– Group range: 233.0.0.0 - 233.255.255.255• Your AS number is inserted in middle two octets

• Remaining low-order octet used for group assignment

– Defined in IETF draft• “draft-ietf-mboned-glop-addressing-00.txt”

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• IGMP

• PIM

• MSDP

• MBGP

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• Routers solicit group membership from directly connected hosts

• RFC 1112 specifies version 1 of IGMP Supported on Windows 95

• RFC 2236 specifies version 2 of IGMP Supported on latest service pack for Windows and most UNIX systems

• IGMP version 3 is specified in IETF draft draft-ietf-idmr-igmp-v3-03.txt

• How hosts tell routers about group membership

Host-Router Signaling: IGMPHost-Router Signaling: IGMP

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H3

• Host sends IGMP Report to join group

H3224.1.1.1

Report

H1 H2

Joining a Group


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• Router sends periodic Queries to 224.0.0.1

Query

• One member per group per subnet reports

224.1.1.1

Report

• Other members suppress reports

224.1.1.1

SuppressedX

224.1.1.1

SuppressedX

H1 H2 H3

Maintaining a Group


19

• Host quietly leaves group

H1 H3H3 #1#1

• Router sends 3 General Queries (60 secs apart)

General Query

#2#2

• No IGMP Report for the group is received• Group times out (Worst case delay ~= 3 minutes)

H2

Leaving a Group (IGMPv1)


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• Host sends Leave message to 224.0.02

H1 H3H3

Leave to224.0.0.2

224.1.1.1

#1#1

• Router sends Group specific query to 224.1.1.1

Group SpecificQuery to 224.1.1.1#2#2

• No IGMP Report is received within ~3 seconds• Group 224.1.1.1 times out

H2

Leaving a Group (IGMPv2)


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• draft-ietf-idmr-igmp-v3-??.txt

• Early implementations now in beta– Enables hosts to listen only to a specified

subset of the hosts sending to the group

IGMPv3IGMPv3

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Source = 1.1.1.1Group = 224.1.1.1

H1 - Member of 224.1.1.1

R1

R3

R2

Source = 2.2.2.2Group = 224.1.1.1

• H1 wants to receive from S = 1.1.1.1 but not from S = 2.2.2.2

• With IGMP, specific sources can be pruned back - S = 2.2.2.2 in this case

IGMPv3:Join 1.1.1.1, 224.1.1.1Leave 2.2.2.2, 224.1.1.1

IGMPv3IGMPv3

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• IGMP

• PIM

• MSDP

• MBGP

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PIMPIM

• Distribution Trees

• Neighbor Discovery

• PIM-DM

• PIM-SM

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Shortest Path or Source Distribution Tree

Receiver 1

B

E

A D F

Source 1Notation: (S, G) S = Source G = Group

C

Receiver 2

Source 2

Multicast Distribution TreesMulticast Distribution Trees

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Receiver 1

B

E

A D F

Source 1Notation: (S, G) S = Source G = Group

C

Receiver 2

Source 2

Multicast Distribution TreesMulticast Distribution Trees

Shortest Path or Source Distribution Tree

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Multicast Distribution Trees

Shared Distribution Tree

Receiver 1

B

E

A D F

Notation: (*, G) * = All Sources G = Group

C

Receiver 2

(RP) PIM Rendezvous Point

Shared Tree

(RP)

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Shared Distribution Tree

Receiver 1

B

E

A F

Source 1 Notation: (*, G) * = All Sources G = Group

C

Receiver 2

Source 2

(RP) PIM Rendezvous Point

Shared Tree

Source Tree

D (RP)

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• Source or Shortest Path treesUses more memory O(S x G) but you get optimal paths from source to all receivers; minimizes delay

• Shared treesUses less memory O(G) but you may get sub-optimal paths from source to all receivers; may introduce extra delay

CharacteristicsCharacteristics of Distribution Trees

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171.68.37.2PIM Router 2

Highest IP Address electedas “DR” (Designated Router)

PIM Hello

PIM Router 1171.68.37.1

PIM Hello

PIM Neighbor DiscoveryPIM Neighbor Discovery

• PIMv2 Hellos are periodically multicast to the “All-PIM-Routers” (224.0.0.13) group address. (Default = 30 seconds)

– Note: PIMv1 multicasts PIM Query messages to the “All-Routers” (224.0.0.2) group address.

• If the “DR” times-out, a new “DR” is elected.

• The “DR” is responsible for sending all Joins and Register messages for any receivers or senders on the network.

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wan-gw8>show ip pim neighborPIM Neighbor TableNeighbor Address Interface Uptime Expires Mode171.68.0.70 FastEthernet0 2w1d 00:01:24 Dense 171.68.0.91 FastEthernet0 2w6d 00:01:01 Dense (DR)171.68.0.82 FastEthernet0 7w0d 00:01:14 Dense 171.68.0.86 FastEthernet0 7w0d 00:01:13 Dense 171.68.0.80 FastEthernet0 7w0d 00:01:02 Dense 171.68.28.70 Serial2.31 22:47:11 00:01:16 Dense 171.68.28.50 Serial2.33 22:47:22 00:01:08 Dense 171.68.27.74 Serial2.36 22:47:07 00:01:21 Dense 171.68.28.170 Serial0.70 1d04h 00:01:06 Dense 171.68.27.2 Serial1.51 1w4d 00:01:25 Dense 171.68.28.110 Serial3.56 1d04h 00:01:20 Dense 171.68.28.58 Serial3.102 12:53:25 00:01:03 Dense

PIM Neighbor DiscoveryPIM Neighbor Discovery

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PIM-DM — EvaluationPIM-DM — Evaluation

• Most effective for small pilot networks

• Advantages:– Easy to configure—two commands

– Simple flood and prune mechanism

• Potential issues...– Inefficient flood and prune behavior

– Complex Assert mechanism

– Mixed control and data planes• Results in (S, G) state in every router in the network

• Can result in non-deterministic topological behaviors

– No support for shared trees

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PIM-SM OverviewPIM-SM Overview

• Explicit join model–Receivers join to the Rendezvous Point (RP)

–Senders register with the RP

–Data flows down the shared tree and goes only to places that need the data from the sources

–Last hop routers can join source tree if the data rate warrants by sending joins to the source

• RPF check depends on tree type–For shared trees, uses RP address

–For source trees, uses Source address

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PIM-SM OverviewPIM-SM Overview

• Only one RP is chosen for a particular group

• RP statically configured or dynamically learned (Auto-RP, PIM v2 candidate RP advertisements)

• Data forwarded based on the source state (S, G) if it exists, otherwise use the shared state (*, G)

• RFC 2326 - “PIM Sparse Mode Protocol Spec”

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PIM-SM Shared Tree JoinPIM-SM Shared Tree Join

Receiver

RP

(*, G) Join

Shared Tree

(*, G) State created onlyalong the Shared Tree.

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PIM-SM Sender RegistrationPIM-SM Sender Registration

Receiver

RP

(S, G) Join

Source

Shared Tree

(S, G) Register (unicast)

Source Tree

(S, G) State created onlyalong the Source Tree.Traffic Flow

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Receiver

RPSource

Shared Tree

Source TreeRP sends a Register-Stop back to the first-hop router to stop the Register process.

(S, G) Register-Stop (unicast)

Traffic Flow

(S, G) Register (unicast)

(S, G) traffic begins arriving at the RP via the Source tree.

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Receiver

RPSource

Shared Tree

Source Tree

Traffic FlowSource traffic flows nativelyalong SPT to RP.

From RP, traffic flows downthe Shared Tree to Receivers.

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PIM-SM SPT SwitchoverPIM-SM SPT Switchover

Receiver

RP

(S, G) Join

Source

Source Tree

Shared Tree

Last-hop router joins the Source Tree.

Additional (S, G) State is created along new part of the Source Tree.

Traffic Flow

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Receiver

RPSource

Source Tree

Shared Tree

(S, G)RP-bit Prune

Traffic begins flowing down the new branch of the Source Tree.

Additional (S, G) State is created along along the Shared Tree to prune off (S, G) traffic.

Traffic Flow

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Receiver

RPSource

Source Tree

Shared Tree

(S, G) Traffic flow is now pruned off of the Shared Tree and is flowing to the Receiver via the Source Tree.

Traffic Flow

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Receiver

RPSource

Source Tree

Shared Tree

(S, G) traffic flow is no longer needed by the RP so it Prunes the flow of (S, G) traffic.

Traffic Flow

(S, G) Prune

43


Receiver

RPSource

Source Tree

Shared Tree

(S, G) Traffic flow is now only flowing to the Receiver via a single branch of the Source Tree.

Traffic Flow

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PIM-SM Protocol MechanicsPIM-SM Protocol Mechanics

• PIM SM StatePIM SM State

• PIM SM Forwarding

• PIM SM Joining

• PIM SM Registering

• PIM SM SPT-Switchover

• PIM SM Pruning

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PIM-SM State ExamplePIM-SM State Example

sj-mbone> show ip mrouteIP Multicast Routing TableFlags: D - Dense, S - Sparse, C - Connected, L - Local, P - Pruned R - RP-bit set, F - Register flag, T - SPT-bit set, J - Join SPT M - MSDP created entry, X - Proxy Join Timer Running A - Advertised via MSDPTimers: Uptime/ExpiresInterface state: Interface, Next-Hop or VCD, State/Mode

(*, 224.1.1.1), 00:13:28/00:02:59, RP 10.1.5.1, flags: SCJ Incoming interface: Ethernet0, RPF nbr 10.1.2.1, Outgoing interface list: Ethernet1, Forward/Sparse, 00:13:28/00:02:32 Serial0, Forward/Sparse, 00:4:52/00:02:08

(171.68.37.121/32, 224.1.1.1), 00:01:43/00:02:59, flags: CJT Incoming interface: Serial0, RPF nbr 192.10.2.1 Outgoing interface list: Ethernet1, Forward/Sparse, 00:01:43/00:02:11 Ethernet0, forward/Sparse, 00:01:43/00:02:11

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PIM-SM (*,G) State RulesPIM-SM (*,G) State Rules

• (*,G) creation– Upon receipt of a (*,G) Join or

– Automatically if (S,G) must be created

• (*,G) reflects default group forwarding– IIF = RPF interface toward RP

– OIL = interfaces• that received a (*,G) Join or• with directly connected hosts or• manually configured

• (*,G) deletion– When OIL = NULL and

– no child (S,G) state exists

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PIM-SM (S,G) State RulesPIM-SM (S,G) State Rules

• (S,G) creation– By receipt of (S,G) Join or Prune or

– By “Register” process

– Parent (*,G) created (if doesn’t exist)

• (S,G) reflects forwarding of “S” to “G”– IIF = RPF Interface normally toward source

• RPF toward RP if “RP-bit” set

– OIL = Initially, copy of (*,G) OIL minus IIF

• (S,G) deletion– By normal (S,G) entry timeout

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PIM-SM OIL RulesPIM-SM OIL Rules

• Interfaces in OIL added – By receipt of Join message

• Intfc’s added to (*,G) are added to all (S,G)’s

• Interfaces in OIL removed – By receipt of Prune message

• Intfc’s removed from (*,G) are removed from all (S,G)’s

– Interface Expire timer counts down to zero• Timer reset (to 3 min.) by receipt of periodic Join or• By IGMP membership report

49

PIM-SM State FlagsPIM-SM State Flags

• S = Sparse Mode

• C = Directly Connected Host

• L = Local (Router is member)

• P = Pruned (All intfcs in OIL = Prune)

• T = Forwarding via SPT– Indicates at least one packet was forwarded

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PIM-SM State Flags (Cont.)PIM-SM State Flags (Cont.)

• J = Join SPT – In (*, G) entry

•Indicates SPT-Threshold is being exceeded•Next (S,G) received will trigger join of SPT

– In (S, G) entry•Indicates SPT joined due to SPT-Threshold•If rate < SPT-Threshold, switch back to Shared Tree

• F = Register – In (S,G) entry

•Indicates the router is a first-hop router and there is a directly connected source or proxy registers are being sent.

– In (*, G) entry•Set when “F” set in at least one child (S,G)

51

PIM-SM State Flags (Cont.)PIM-SM State Flags (Cont.)

• R = RP bit– (S, G) entries only

– Set by (S,G)RP-bit Prune/Join

– Indicates info is applicable to Shared Tree

– Used to prune (S,G) traffic from Shared Tree• Initiated by Last-hop router after switch to SPT

– Modifies (S,G) forwarding behavior• IIF = RPF toward RP (I.e. up the Shared Tree)• OIL = Pruned accordingly

52


• PIM SM State

• PIM SM ForwardingPIM SM Forwarding

• PIM SM Joining



• PIM SM Pruning

53

PIM-SM Forwarding RulesPIM-SM Forwarding Rules

• Use longest match entry– Use (S, G) entry if exists

– Otherwise, use (*, G) entry

• RPF check first– If Packet didn’t arrive via IIF, drop it.

• Forward Packet (if RPF succeeded)– Send out all “unpruned” interfaces in OIL

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E0

S0

rtr-a

S1

• Packets are “forwarded” out all interfaces in “oilist”.

• PIM Sparse mode interfaces are placed on the “oilist” for a Multicast Group IF:

– PIM neighbor Joins the group on this interface

– Host on this interface has joined the group

– Interface has been manually configured to join group.

Shared TreeMulticast Packets

(128.9.160.1, 224.1.1.1)

Source Tree (SPT)Multicast Packets

(128.9.160.43, 224.1.1.1)

E0E1

Rcvr A(*, 224.1.1.1)

to RP(10.1.5.1)

PIM SM ForwardingPIM SM Forwarding

55


• PIM SM State


• PIM SM JoiningPIM SM Joining



• PIM SM Pruning

56

PIM SM JoiningPIM SM Joining

• Leaf routers send a (*,G) Join to toward RP– Joins sent hop-by-hop via unicast path toward RP

• Each router along path creates (*,G) state– IF no (*,G) state, create it & send a Join toward RP

– ELSE Join process complete. Reached the (*,G) tree.

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• “Rcvr A” wishes to receive group G traffic. Sends IGMP Join for G.11

IGMP Join11

E0S0 rtr-a

rtr-b

S1

E0E1

Rcvr A

Shared Tree

To RP (10.1.5.1)

10.1.2.2

10.1.2.110.1.4.2


58

(*, 224.1.1.1), 00:00:05/00:02:54, RP 10.1.5.1, flags: SC Incoming interface: Ethernet0, RPF nbr 10.1.2.1 Outgoing interface list: Ethernet1, Forward/Sparse, 00:00:05/00:02:54

(*, 224.1.1.1), 00:00:05/00:02:54, RP 10.1.5.1, flags: SC Incoming interface: Ethernet0, RPF nbr 10.1.2.1 Outgoing interface list: Ethernet1, Forward/Sparse, 00:00:05/00:02:54

“rtr-b” creates (*, 224.1.1.1) state

E0S0 rtr-a

rtr-b

S1

E0E1

To RP (10.1.5.1)

Rcvr A

Shared Tree

10.1.2.2

10.1.2.110.1.4.2


Ethernet1, Forward/Sparse, 00:00:05/00:02:54

59


• “rtr-b” sends (*,G) Join towards RP.22

PIM Join22

E0S0 rtr-a

rtr-b

S1

E0E1

Rcvr A

Shared Tree

To RP (10.1.5.1)

10.1.2.2

10.1.2.110.1.4.2


60

(*, 224.1.1.1), 00:00:05/00:02:54, RP 10.1.5.1, flags: S Incoming interface: Serial0, RPF nbr 10.1.4.1 Outgoing interface list: Ethernet0, Forward/Sparse, 00:00:05/00:02:54

(*, 224.1.1.1), 00:00:05/00:02:54, RP 10.1.5.1, flags: S Incoming interface: Serial0, RPF nbr 10.1.4.1 Outgoing interface list: Ethernet0, Forward/Sparse, 00:00:05/00:02:54

“rtr-a” creates (*, 224.1.1.1) state.

E0S0 rtr-a

rtr-b

S1

E0E1

To RP (10.1.5.1)

Rcvr A

Shared Tree

10.1.2.2

10.1.2.110.1.4.2

PIM SM Joining PIM SM Joining

Ethernet0, Forward/Sparse, 00:00:05/00:02:54

61

PIM Join33

Shared Tree44

• Shared tree is built all the way back to the RP.44

E0S0 rtr-a

rtr-b

S1

E0E1

Rcvr A

Shared Tree

To RP (10.1.5.1)

10.1.2.2

10.1.2.110.1.4.2



• “rtr-a” sends (*,G) Join towards RP.33

• “rtr-b” sends (*,G) Join towards RP.22

62


• PIM SM State


• PIM SM Joining

• PIM SM RegisteringPIM SM Registering


• PIM SM Pruning

63

PIM SM RegisteringPIM SM Registering

• Senders begin sourcing Multicast Traffic– Senders don’t necessarily perform IGMP group joins.

• 1st-hop router unicasts “Registers” to RP– A Mcast packet is encapsulated in each Register msg

– Registers messages follow unicast path to RP

• RP receives “Register” messages– De-encapsulates the Mcast packet inside Register msg

– Forwards Mcast packet down Shared Tree

– Sends (S,G) Join toward Source / 1st-Hop router to build an (S,G) SPT between Source and RP

64

PIM SM RegisteringPIM SM Registering

• 1st-hop router receives (S,G) Join– SPT between Source and RP now built.

– Begins forwarding traffic down (S,G) SPT to RP

– (S,G) Traffic temporarily flowing down 2 paths to RP

• RP receives traffic down native (S,G) SPT– Sends a “Register-Stop” msg to Source / 1st-Hop router.

• 1st-Hop router receives “Register-Stop” msg– Stops encapsulating traffic in “Register” messages

– (S,G) Traffic now flowing down single SPT to RP

65

PIM SM Register ExamplesPIM SM Register Examples

• Receivers Join Group FirstReceivers Join Group First

• Source Registers First

66

(*, 224.1.1.1), 00:00:03/00:02:56, RP 171.68.28.140, flags:S Incoming interface: Null, RPF nbr 0.0.0.0, Outgoing interface list: Serial0, Forward/Sparse, 00:03:14/00:02:59 Serial1, Forward/Sparse, 00:03:14/00:02:59

State in “RP” before any source registers(with receivers on Shared Tree)

rtr-a

RP

rtr-crtr-b

Shared Tree

S3S0 S1

PIM SM RegisteringReceiver Joins Group First


E0 S1S0S0

67

rtr-b>sh ip mroute 224.1.1.1

No such group

rtr-b>sh ip mroute 224.1.1.1

No such group

State in “rtr-b” before any source registers(with receivers on Shared Tree)

rtr-a

RP

rtr-crtr-b

Shared Tree

E0



S3S0 S1

S1S0S0

68

rtr-a>sh ip mroute 224.1.1.1

No such group.

State in “rtr-a” before any source registers(with receivers on Shared Tree)

rtr-a

RP

rtr-crtr-b

Shared Tree

E0



S3S0 S1

S1S0S0

69

11

(171.68.37.121, 224.1.1.1) Mcast Packets

rtr-a

RP

Source 171.68.37.121 rtr-crtr-b

Shared Tree



E0 S3S0 S1

• “Source” begins sending group G traffic. 11

S1S0S0

70

(*, 224.1.1.1), 00:00:03/00:02:56, RP 171.68.28.140, flags: SP Incoming interface: Serial0, RPF nbr 171.68.28.191, Outgoing interface list: Null

(171.68.37.121/32, 224.1.1.1), 00:00:03/00:02:56, flags: FPT Incoming interface: Ethernet0, RPF nbr 0.0.0.0, Outgoing interface list: Null



“rtr-a” creates (S, G) state for source(After automatically creating a (*, G) entry)

(171.68.37.121, 224.1.1.1) Mcast Packets

Source 171.68.37.121

rtr-a

RP

Shared Tree

rtr-crtr-b



E0 S3S0 S1

• “rtr-a” encapsulates packets in Registers; unicasts to RP.22

Register Msgs22


RegisteringFPT

S1S0S0

71

Register Msgs

“RP” processes Register; creates (S, G) state

(*, 224.1.1.1), 00:09:21/00:02:38, RP 171.68.28.140, flags: S Incoming interface: Null, RPF nbr 0.0.0.0, Outgoing interface list: Serial0, Forward/Sparse, 00:09:21/00:02:38 Serial1, Forward/Sparse, 00:03:14/00:02:46

(171.68.37.121, 224.1.1.1, 00:01:15/00:02:46, flags: Incoming interface: Serial3, RPF nbr 171.68.28.139, Outgoing interface list: Serial0, Forward/Sparse, 00:00:49/00:02:11 Serial1, Forward/Sparse, 00:00:49/00:02:11

(171.68.37.121, 224.1.1.1) Mcast Packets

Source 171.68.37.121

rtr-a

RP

Shared Tree

rtr-crtr-b



E0 S3S0 S1

• “rtr-c” (RP) de-encapsulates packets; forwards down Shared tree.33

33 (*, 224.1.1.1)Mcast Traffic

171.68.28.139

S1S0S0

72

Register Msgs

rtr-a

RP

rtr-c

Shared Tree

(*, 224.1.1.1)Mcast Traffic

(171.68.37.121, 224.1.1.1) Mcast Packets

Source 171.68.37.121



E0S0 S1

rtr-b

• RP sends (S,G) Join toward Source to build SPT.44

S1

Join S044

S0S0

73

Register Msgs

E0

“rtr-b” processes Join, creates (S, G) state(After automatically creating the (*, G) entry)


(171.68.37.121/32, 224.1.1.1), 00:04:28/00:01:32, flags: Incoming interface: Serial0, RPF nbr 171.68.28.190 Outgoing interface list: Serial1, Forward/Sparse, 00:04:28/00:01:32



rtr-a

RP

rtr-crtr-b

Shared Tree


Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets

S1

171.68.28.190



S0 S1

• “rtr-b” sends (S,G) Join toward Source to continue building SPT.55

Join S055

• RP sends (S,G) Join toward Source to build SPT.44

S0S0

74

Register Msgs


(171.68.37.121/32, 224.1.1.1), 00:04:28/00:01:32, flags: FT Incoming interface: Ethernet0, RPF nbr 0.0.0.0, Registering Outgoing interface list:



“rtr-a” processes the (S, G) Join; adds Serial0 to OIL

rtr-a

RP

rtr-crtr-b

Shared Tree


Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets

E0



S0 S1

Serial0, Forward/Sparse, 00:04:28/00:01:32

S1S0S0

75

Register Msgs

S0 S1E0

• RP begins receiving (S,G) traffic down SPT. 66

66

• RP sends “Register-Stop” to “rtr-a”.77

Register-Stop77

rtr-a

RP

rtr-crtr-b

Shared Tree


Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets



S1S0S0

76


(171.68.37.121/32, 224.1.1.1), 00:04:28/00:01:32, flags: FT Incoming interface: Ethernet0, RPF nbr 0.0.0.0, Registering Outgoing interface list: Serial0, Forward/Sparse, 00:04:28/00:01:32


(171.68.37.121/32, 224.1.1.1), 00:04:28/00:01:32, flags: FT Incoming interface: Ethernet0, RPF nbr 0.0.0.0, Registering Outgoing interface list: Serial0, Forward/Sparse, 00:04:28/00:01:32

rtr-a

RP

rtr-crtr-b

Shared Tree


Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets



E0 S3S0 S1

S1S0S0

“rtr-a” stops sending Register messages(Final State in “rtr-a”)

• (S,G) Traffic now flowing down a single path (SPT) to RP.88

88

77

Final state in “rtr-b”


(171.68.37.121/32, 224.1.1.1), 00:04:28/00:01:32, flags: T Incoming interface: Serial0, RPF nbr 171.68.28.190 Outgoing interface list: Serial1, Forward/Sparse, 00:04:28/00:01:32



rtr-a

RP

rtr-crtr-b

Shared Tree


Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets

E0



S0 S1S1S0S0

78

Final state in the “RP”(with receivers on Shared Tree)

(*, 224.1.1.1), 00:09:21/00:02:38, RP 171.68.28.140, flags: S Incoming interface: Null, RPF nbr 0.0.0.0, Outgoing interface list: Serial0, Forward/Sparse, 00:09:21/00:02:38 Serial1, Forward/Sparse, 00:03:14/00:02:46

(171.68.37.121, 224.1.1.1, 00:01:15/00:02:46, flags: T Incoming interface: Serial3, RPF nbr 171.68.28.139, Outgoing interface list: Serial0, Forward/Sparse, 00:00:49/00:02:11 Serial1, Forward/Sparse, 00:00:49/00:02:11

rtr-a

RP

rtr-crtr-b

Shared Tree


Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets

S3

171.68.28.139



S0 S1S1S0S0E0

79

PIM SM Register ExamplesPIM SM Register Examples

• Receivers Join Group First

• Source Registers FirstSource Registers First

80

rtr-c>show ip mroute 224.1.1.1

Group 224.1.1.1 not found.

rtr-c>show ip mroute 224.1.1.1


State in “RP” before Registering(without receivers on Shared Tree)

rtr-a

RP

rtr-crtr-b

S3S0

S1S0S0E0S1

PIM SM RegisteringSource Registers First


81

rtr-b>show ip mroute 224.1.1.1




State in “rtr-b” before any source registers(with receivers on Shared Tree)

rtr-a

RP

rtr-b



rtr-cS3

S0S1S0S0E0

S1

82

rtr-a>show ip mroute 224.1.1.1


State in “rtr-a” before any source registers(with receivers on Shared Tree)

rtr-a

RP

rtr-b



rtr-cS3

S0S1S0S0E0

S1

83

11

(171.68.37.121, 224.1.1.1) Mcast Packets

rtr-a

RP

Source 171.68.37.121

rtr-b




rtr-cS3

S0S1S0S0E0

S1

84





“rtr-a” creates (S, G) state for source(After automatically creating a (*, G) entry)

(171.68.37.121, 224.1.1.1) Mcast Packets

Source 171.68.37.121

rtr-a

RP

rtr-b



• “rtr-a” encapsulates packets in Registers; unicasts to RP.22

Register Msgs22


RegisteringFPT

rtr-cS3

S0S1S0S0E0

S1

85

“RP” processes Register; creates (S, G) state(After automatically creating the (*, G) entry)

(*, 224.1.1.1), 00:01:15/00:01:45, RP 171.68.28.140, flags: S Incoming interface: Null, RPF nbr 0.0.0.0, Outgoing interface list: Null

(171.68.37.121, 224.1.1.1), 00:01:15/00:01:45, flags: P Incoming interface: Serial3, RPF nbr 171.68.28.139, Outgoing interface list: Null

(171.68.37.121, 224.1.1.1) Mcast Packets

Register Msgs

Source 171.68.37.121

rtr-a

RP

rtr-b



171.68.28.139

• “rtr-c” (RP) has no receivers on Shared Tree; discards packet.33

33

rtr-cS3

S0S1S0S0E0

S1

86


RP

(171.68.37.121, 224.1.1.1) Mcast Packets

Register Msgs

Source 171.68.37.121

Register-Stop 44

rtr-c




rtr-cS3

S0S1S0S0E0

S1rtr-a rtr-b

87

RP

(171.68.37.121, 224.1.1.1) Mcast Packets

Source 171.68.37.121

55

• “rtr-a” stops encapsulating traffic in Register Messages; drops packets from Source.

55





rtr-cS3

S0S1S0S0E0

S1rtr-a rtr-b

88


(171.68.37.121/32, 224.1.1.1), 00:01:28/00:01:32, flags: FPT Incoming interface: Ethernet0, RPF nbr 0.0.0.0 Outgoing interface list: Null


(171.68.37.121/32, 224.1.1.1), 00:01:28/00:01:32, flags: FPT Incoming interface: Ethernet0, RPF nbr 0.0.0.0 Outgoing interface list: Null

State in “rtr-a” after Registering(without receivers on Shared Tree)

RP

Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets



rtr-cS3

S0S1S0S0E0

S1rtr-a rtr-b

89





State in “rtr-b” after “rtr-a” Registers(without receivers on Shared Tree)

RP

Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets

rtr-c



rtr-cS3

S0S1S0S0E0

S1rtr-a rtr-b

90

State in “RP” after “rtr-a” Registers(without receivers on Shared Tree)





RP

Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets

171.68.28.139



rtr-cS3

S0S1S0S0E0

S1rtr-a rtr-b

91

rtr-cS3

S0S1S0S0E0

S1

RP

• RP (“rtr-c”) receives (*, G) Join from a receiver on Shared Tree. 66

(*, G) Join 66

Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets

Receivers begin joining the Shared Tree



rtr-a rtr-b

92

“RP” processes (*,G) Join(Adds Serial1 to Outgoing Interface Lists)

(*, 224.1.1.1), 00:09:21/00:02:38, RP 171.68.28.140, flags: S Incoming interface: Null, RPF nbr 0.0.0.0, Outgoing interface list:

(171.68.37.121/32, 224.1.1.1, 00:01:15/00:02:46, flags: T Incoming interface: Serial3, RPF nbr 171.68.28.139, Outgoing interface list:

RP

Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets



rtr-cS3

S0S1S0S0E0

S1



Join 77

• RP sends (S,G) Joins for all known Sources in Group.77

rtr-a rtr-b

93

“rtr-b” processes Join, creates (S, G) state(After automatically creating the (*, G) entry)





RP

Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets

171.68.28.190

• “rtr-b” sends (S,G) Join toward Source to continue building SPT.88

Join S088

rtr-cS3S1S0S0E0

• RP sends (S,G) Joins for all known Sources in Group.77



S0 S1

Join 77

rtr-a rtr-b

94





“rtr-a” processes the (S, G) Join; adds Serial0 to OIL


RP

Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets



rtr-cS3

S0S1S0S0E0

S1

99

• RP begins receiving (S,G) traffic down SPT.99

1010 (*, 224.1.1.1)Mcast Traffic

1010• RP forwards (S,G) traffic down Shared Tree to receivers.1010

rtr-a rtr-b

95





Final state in “rtr-b” after Receivers Join

RP

Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets


171.68.28.190



rtr-cS3

S0S1S0S0E0

S1rtr-a rtr-b

96

Final state in “RP” after Receivers Join

(*, 224.1.1.1), 00:09:21/00:02:38, RP 171.68.28.140, flags: S Incoming interface: Null, RPF nbr 0.0.0.0, Outgoing interface list: Serial1, Forward/Sparse, 00:03:14/00:02:46

(171.68.37.121/32, 224.1.1.1, 00:01:15/00:02:46, flags: T Incoming interface: Serial3, RPF nbr 171.68.28.139, Outgoing interface list: Serial1, Forward/Sparse, 00:00:49/00:02:11

RP

Source 171.68.37.121

(171.68.37.121, 224.1.1.1) Mcast Packets


171.68.28.139



rtr-cS3

S0S1S0S0E0

S1rtr-a rtr-b

97

PIM SM SPT-SwitchoverPIM SM SPT-Switchover

• SPT Thresholds may be set for any Group– Access Lists may be used to specify which Groups

– Default Threshold = 0kbps (I.e. immediately join SPT)

– Threshold = “infinity” means “never join SPT”.

• Threshold triggers Join of Source Tree– Sends an (S,G) Join up SPT for next “S” in “G” packet

received.

• Pros– Reduces Network Latency

• Cons– More (S,G) state must be stored in the routers.

98

Once each second– Compute new (*, G) traffic rate– If threshold exceeded, set “J” flag in (*, G)

For each (Si , G) packet received:

– If “J” flag set in (*, G)• Join SPT for (Si , G)

• Mark (Si , G) entry with “J” flag

• Clear “J” flag in (*,G)

Once each second– Compute new (*, G) traffic rate– If threshold exceeded, set “J” flag in (*, G)

For each (Si , G) packet received:

– If “J” flag set in (*, G)• Join SPT for (Si , G)

• Mark (Si , G) entry with “J” flag

• Clear “J” flag in (*,G)

SPT-Switchover Mechanism


99

State in “rtr-c” before switch

(*, 224.1.1.1), 00:01:43/00:02:13, RP 10.1.5.1, flags: S Incoming interface: Serial0, RPF nbr 10.1.5.1, Outgoing interface list: Serial1, Forward/Sparse, 00:01:43/00:02:11 Serial2, Forward/Sparse, 00:00:32/00:02:28

E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c

To Source “Si”To RP (10.1.5.1)

S0

E0

Rcvr B

rtr-d

S2

S0


(Si, G) Traffic FlowShared (RPT) Tree

SPT Tree

100

State in “rtr-d” before switch

(*, 224.1.1.1), 00:01:43/00:02:13, RP 10.1.5.1, flags: SC Incoming interface: Serial0, RPF nbr 10.1.4.8, Outgoing interface list: Ethernet0, Forward/Sparse, 00:01:43/00:02:11

E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

E0

Rcvr B

rtr-d

S2

S0



SPT Tree

101

(*, 224.1.1.1), 00:01:43/00:02:13, RP 10.1.5.1, flags: S Incoming interface: Serial0, RPF nbr 10.1.4.1, Outgoing interface list: Ethernet0, Forward/Sparse, 00:01:43/00:02:11

State in “rtr-a” before switch

E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

E0

Rcvr B

rtr-d

S2

S0



SPT Tree

102

State in “rtr-b” before switch

(*, 224.1.1.1), 00:01:43/00:02:13, RP 10.1.5.1, flags: SC Incoming interface: Ethernet0, RPF nbr 10.1.2.1, Outgoing interface list: Ethernet1, Forward/Sparse, 00:01:43/00:02:11

E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

E0

Rcvr B

rtr-d

S2

S0



SPT Tree

103


Group “G” rate exceeds SPT Threshold at “rtr-b”;11

Set J Flag in (*, G) and wait for next (Si,G) packet.22

22


J

E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

E0

Rcvr B

rtr-d

S2

S0


SPT Tree

Group “G” rate > Threshold11

104


J


(Si,G) packet arrives down Shared tree.33

Clear J Flag in the (*,G) & create (Si,G) state.44

44

33

E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

E0

Rcvr B

rtr-d

S2

S0


SPT Tree

105

New State in “rtr-b”


(171.68.37.121/32, 224.1.1.1), 00:13:28/00:02:53, flags: CJT Incoming interface: Ethernet0, RPF nbr 10.1.2.1 Outgoing interface list: Ethernet1, Forward/Sparse, 00:13:28/00:02:53


E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

E0

Rcvr B

rtr-d

S2

S0


SPT Tree

J Flag indicates(S, G) created by

exceeding theSPT-threshold

CJT

106


55Send (Si,G) Join towards Si .

E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

E0

Rcvr B

rtr-d

S2

S0


SPT Tree

(Si,G) Join55

107


SPT Tree


(171.68.37.121/32, 224.1.1.1), 00:13:28/00:02:53, flags: T Incoming interface: Serial1, RPF nbr 10.1.9.2 Outgoing interface list: Ethernet0, Forward/Sparse, 00:13:25/00:02:30

New state in “rtr-a”


E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

E0

Rcvr B

rtr-d

S2

S0

108


“rtr-a” forwards (Si,G) Join toward Si.66

(Si,G) Join66

SPT & RPT diverge, triggering (Si,G)RP-bit Prunes toward RP.77

(Si,G)RP-bit Prune77

E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

E0

Rcvr B

rtr-d

S2

S0


SPT Tree

109


(Si, G) traffic begins flowing down SPT tree.88

(Si,G) Traffic88

E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

E0

Rcvr B

rtr-d

S2

S0


SPT Tree

110

E0

Rcvr B


SPT Tree

(*, 224.1.1.1), 00:01:43/00:02:13, RP 10.1.5.1, flags: S Incoming interface: Serial0, RPF nbr 10.1.5.1, Outgoing interface list: Serial1, Forward/Sparse, 00:01:43/00:02:11 Serial2, Forward/Sparse, 00:00:32/00:02:28

(171.68.37.121/32, 224.1.1.1), 00:13:28/00:02:53, flags: R Incoming interface: Serial0, RPF nbr 10.1.5.1 Outgoing interface list: Serial2, Forward/Sparse, 00:00:32/00:02:28

State in “rtr-c” after receiving the (Si, G) RP-bit Prune


E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

rtr-d

S2

S0

111


E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

E0

Rcvr B

rtr-d

S2

S0


SPT Tree

• Unnecessary (Si, G) traffic is pruned from the Shared tree.99

99

112


E0S0

rtr-a

rtr-b

S1

E0E1

Rcvr A

10.1.2.2

10.1.2.110.1.4.2

S110.1.4.1

rtr-c


S0

E0

Rcvr B

rtr-d

S2

S0


SPT Tree

• Unnecessary (Si, G) traffic is pruned from the Shared tree.99

• (Si, G) traffic still flows via other branches of the Shared tree.1010

1010

113

Shared Tree Switchback Mechanism


• Once each second when the (S,G) state is older than 1 minute

– If “J” flag set in (Si , G) entry• Compute new (Si , G) traffic rate

• If rate < SPT-threshold– Rejoin (*, G) Tree for (Si , G) traffic

– Send (Si , G) prune up SPT toward Si

– Delete (Si , G) entry

• Once each second when the (S,G) state is older than 1 minute

– If “J” flag set in (Si , G) entry• Compute new (Si , G) traffic rate

• If rate < SPT-threshold– Rejoin (*, G) Tree for (Si , G) traffic

– Send (Si , G) prune up SPT toward Si

– Delete (Si , G) entry

114


• PIM SM State


• PIM SM Joining



• PIM SM PruningPIM SM Pruning

115

• IGMP group times out / last host sends Leave

• Interface removed from all (*,G) and (S,G) entries

– IF all interfaces in “oilist” for (*,G) are pruned; THEN send Prune up shared tree toward RP

– Any (S, G) state allowed to time-out

• Each router along path “prunes” interface

– IF all interfaces in “oilist” for (*,G) are pruned; THEN send Prune up shared tree toward RP

– Any (S, G) state allowed to time-out

PIM SM PruningPIM SM Pruning

116


State in “rtr-b” before Pruning

S0 rtr-a

rtr-b

S1

E0E1

Rcvr A

To RP (10.1.5.1)

10.1.2.2

10.1.2.110.1.4.2

E0(Si, G) Traffic FlowShared Tree

SPT Tree

PIM SM Pruning Shared Tree Case


117


State in “rtr-a” before Pruning

S0 rtr-a

rtr-b

S1

E0E1

Rcvr A

To RP (10.1.5.1)


SPT Tree



10.1.2.2

10.1.2.110.1.4.2

118

“rtr-b” is a Leaf router. Last host “Rcvr A”, leaves group G. 11

S0 rtr-a

rtr-b

S1

E0E1

Rcvr A

To RP (10.1.5.1)

IGMP Leave11

“rtr-b” removes E1 from (*,G) and any (Si,G) “oilists”.22

22

XX“rtr-b” (*,G) “oilist” now empty; sends (*,G) Prune toward RP.33

(*,G) Prune33


SPT Tree



10.1.2.2

10.1.2.110.1.4.2

119

“rtr-a” receives Prune; removes E0 from (*,G) “oilist”. (After the 3 second Multi-access Network Prune delay.)

44

44

“rtr-a” (*,G) “oilist” now empty; send (*,G) Prune toward RP.55

(*,G) Prune55

Pruning continues back toward RP.66



S0 rtr-a

rtr-b

S1

E0E1

To RP (10.1.5.1)


SPT Tree 10.1.2.2

10.1.2.110.1.4.2

XX

XX66

120





State in “rtr-b” before Pruning

S0 rtr-a

rtr-b

S1

E0E1

Rcvr A

To RP (10.1.5.1)

E0

To Source “Si”

(Si, G) Traffic FlowShared Tree

SPT Tree 10.1.2.2

10.1.2.110.1.4.2

PIM SM PruningSource (SPT) Case


121


(171.68.37.121/32, 224.1.1.1), 00:01:05/00:01:55, flags: T Incoming interface: Serial1, RPF nbr 10.1.9.2 Outgoing interface list: Ethernet0, Forward/Sparse, 00:01:05/00:02:55

State in “rtr-a” before Pruning



S0 rtr-a

rtr-b

S1

E0E1

Rcvr A

To RP (10.1.5.1)

E0

To Source “Si”


SPT Tree 10.1.2.2

10.1.2.110.1.4.2

122


IGMP Leave11


22

“rtr-b” (*,G) “oilist” now empty; sends (*,G) Prune toward RP.33

(*,G) Prune33



S0 rtr-a

rtr-b

S1

E0E1

Rcvr A

To RP (10.1.5.1)

E0

To Source “Si”


SPT Tree 10.1.2.2

10.1.2.110.1.4.2

XX

123

“rtr-b” stops sending periodic (S, G) joins.44



“rtr-b” (*,G) “oilist” now empty; sends (*,G) Prune toward RP.33



S0 rtr-a

rtr-b

S1

E0E1

Rcvr A

To RP (10.1.5.1)

E0

To Source “Si”


SPT Tree 10.1.2.2

10.1.2.110.1.4.2

XX

Periodic(S, G) Join

44

XX

124

“rtr-a” receives Prune; removes E0 from (*,G) “oilist”. (After the 3 second Multiaccess Network Prune delay.)

55

55

“rtr-a” (*,G) “oilist” now empty; sends (*,G) Prune toward RP.66

(*,G) Prune66



S0 rtr-a

rtr-b

S1

E0E1

To RP (10.1.5.1)

E0

To Source “Si”


SPT Tree 10.1.2.2

10.1.2.110.1.4.2

XX

125

(*, 224.1.1.1), 00:02:32/00:02:59, RP 10.1.5.1, flags: SP Incoming interface: Ethernet0, RPF nbr 10.1.2.1, Outgoing interface list:

(171.68.37.121/32, 224.1.1.1), 00:01:56/00:00:53, flags: PT Incoming interface: Ethernet0, RPF nbr 10.1.2.1 Outgoing interface list:

State in “rtr-b” after Pruning



S0 rtr-a

rtr-b

S1

E0E1

To RP (10.1.5.1)

E0

To Source “Si”


SPT Tree 10.1.2.2

10.1.2.110.1.4.2

126

(*, 224.1.1.1), 00:02:32/00:02:59, RP 10.1.5.1, flags: SP Incoming interface: Serial0, RPF nbr 10.1.4.1, Outgoing interface list:

(171.68.37.121/32, 224.1.1.1), 00:01:56/00:00:53, flags: PT Incoming interface: Serial1, RPF nbr 10.1.9.2 Outgoing interface list:

(*, 224.1.1.1), 00:02:32/00:02:59, RP 10.1.5.1, flags: SP Incoming interface: Serial0, RPF nbr 10.1.4.1, Outgoing interface list:

(171.68.37.121/32, 224.1.1.1), 00:01:56/00:00:53, flags: PT Incoming interface: Serial1, RPF nbr 10.1.9.2 Outgoing interface list:

State in “rtr-a” after Pruning



S0 rtr-a

rtr-b

S1

E0E1

To RP (10.1.5.1)

E0

To Source “Si”


SPT Tree 10.1.2.2

10.1.2.110.1.4.2

127

Another (Si,G) data packet arrives via Serial1.77

‘rtr-a’ responds by sending an (Si,G) Prune toward source.88

(Si,G) Data 77



S0 rtr-a

rtr-b

S1

E0E1

To RP (10.1.5.1)

E0

To Source “Si”


SPT Tree 10.1.2.2

10.1.2.110.1.4.2

(Si,G) Prune88

128

99

(Si,G) traffic ceases flowing down SPT.99



S0 rtr-a

rtr-b

S1

E0E1

To RP (10.1.5.1)

E0

To Source “Si”


SPT Tree 10.1.2.2

10.1.2.110.1.4.2

Another (Si,G) data packet arrives via Serial1.77

‘rtr-a’ responds by sending an (Si,G) Prune toward source.88

129



• IGMP

• PIM

• MSDP

• MBGP

130

MSDP—Multicast SourceDiscovery Protocol

MSDP—Multicast SourceDiscovery Protocol

• MSDP concepts

• MSDP design points

• MSDP example

• Cisco MSDP implementation

• MSDP configuration

• MSDP application—Anycast RP

131

MSDP ConceptMSDP Concept

• Simple but elegant – Utilize inter-domain source trees

– Reduces problem to locating active sources

– RP or receiver last-hop can join inter-domain source tree

132

MSDP ConceptsMSDP Concepts

• Works with PIM-SM only– RP’s knows about all sources in a domain

• Sources cause a “PIM Register” to the RP• Can tell RP’s in other domains of its sources

– Via MSDP SA (Source Active) messages

– RP’s know about receivers in a domain• Receivers cause a “(*, G) Join” to the RP• RP can join the source tree in the peer domain

– Via normal PIM (S, G) joins

133

SA Message192.1.1.1, 224.2.2.2

Domain C

Domain B

Domain D

Domain E

SA

SA

SA SA

SA

SA

Source ActiveMessages

SA

Domain A

SA Message192.1.1.1, 224.2.2.2

r

Join (*, 224.2.2.2)

MSDP Peers

RP

RP

RP

RP

MSDP OverviewMSDP Overview

sRP

Register192.1.1.1, 224.2.2.2

MSDP Example

134

Domain C

Domain B

Domain D

Domain E

Domain A

RP

RP

RP

RP

r

MSDP Peers

Join

(S

, 224

.2.2

.2)

RP


s

MSDP Example

135

Domain C

Domain B

Domain D

Domain E

Domain A

RP

RP

RP

RP

r

MSDP Peers

Multicast Traffic RP


s

MSDP Example

136

Domain C

Domain B

Domain D

Domain E

Domain A

RP

RP

RP

RP

r

MSDP Peers



s

Join

(S, 224.2.2.2)

MSDP Example

137

Domain C

Domain B

Domain D

Domain E

Domain A

RP

RP

RP

RP

r

MSDP Peers



s

MSDP Example

138

MSDP Design PointsMSDP Design Points

• MSDP peers talk via TCP connections

• Source Active (SA) messages– Peer-RPF forwarded to prevent loops

• RPF check on AS-PATH back to the peer RP– other rules from draft apply

• If successful, flood SA message to other peers• Stub sites can be configured to accept all SA messages

(similar to static default for routing)– Since they have only one exit (e.g., default peer)

– MSDP speaker may cache SA messages• Reduces join latency

139

MSDP PeersMSDP Peers

• MSDP establishes a neighbor relationship between MSDP peers– Peers connect using TCP port 639

– Peers send keepalives every 60 secs (fixed)

– Peer connection reset after 75 seconds if no MSDP packets or keepalives are received

• MSDP peers must run BGP!– May be an MBGP peer, a BGP peer or both

– Exception: BGP is unnecessary when peering with only a single MSDP peer.

140

MSDP SA MessagesMSDP SA Messages

• MSDP SA Message Contents– One or more messages (in TLV format)

• Keepalives• Source Active (SA) Messages• Source Active Request (SA-Req) Messages• Source Active Response (SA-Resp) Message

– Source Active (SA) Messages• Used to advertise active Sources in a domain• Can also carry initial multicast packet from source

– Hack for Bursty Sources (ala SDR)• SA Message Contents:

– IP Address of Originator (usually an RP)– Number of (S, G)’s pairs being advertised– List of active (S, G)’s in the domain– Encapsulated Multicast packet

141

MSDP SA MessagesMSDP SA Messages

• MSDP Message Contents (cont.)– SA Request (SA-Req) Messages

• Used to request a list of active sources for a group– Sent to an MSDP SA Cache Server– Reduces Join Latency to active sources

• SA Request Messages contain:– Requested Group Address

– SA Response (SA-Resp) Messages• Sent in response to an SA Request message• SA Response Messages contain:

– IP Address of Originator (usually an RP)– Number of (S, G)’s pairs being advertised– List of active (S, G)’s in the domain

– Keepalive messages• Used to keep MSDP peer connection up

142

Receiving SA MessagesReceiving SA Messages

• Skip RPF Check and process SA if:– Sending MSDP peer = only MSDP peer

(i.e. the ‘default-peer’ or only ‘msdp-peer’ configured.)

– Sending MSDP peer = Mesh-Group peer

• RPF Check the received SA message.– Lookup best BGP path to RP in SA message

• Search MBGP RIB first then BGP RIB– If path to RP not found, RPF Check Fails; ignore SA message

– Sending MSDP Peer = BGP peer?• Yes: Is best path to RP via this BGP peer?

– If yes, RPF Check Succeeds; process SA message• No: Is next AS in best path to RP = AS of MSDP peer?

– If yes, RPF Check Succeeds; process SA message

143

Receiving SA MessagesReceiving SA Messages

• Detailed RPF Check rules– Case 1: Sending MSDP Peer = iBGP peer

• Is best path to RP via this BGP peer?– Translation: Is the address of the iBGP peer that advertised

the best path to the RP = address of the sending MSDP peer?

– Case 2: Sending MSDP Peer = eBGP peer• Is best path to RP via this BGP peer?

– Translation: Is the AS of eBGP peer = next AS in the best path to the RP?

– Case 3: Sending MSDP Peer != BGP peer• Is the next AS in best path to RP = AS of the sending

MSDP peer?– Translation: None needed.

144

MSDP/iMBGP mesh-peering

MSDP SA

AS1

A

3.1

4.2

4.12.1

ip pim rp-address 172.16.0.2

BGP Table router B

Network Next Hop Path*> 172.16.0.2/32 172.16.3.1 i

MSDP Peers router B

MSDP Peer AS State 172.16.3.1 1 UP 172.16.4.1 1 UP

RPF Success!

Who is the iBGP peer adverting this route,in our example 172.16.3.1

Is the MSDP == BGP peer

RPF rule when MSDP == internal (m)BGP peer

Source

B

CRP

B

RPF Check Example

145

AS1

MSDP/iMBGP mesh-peering

MSDP SA

BGP Table router B

Network Next Hop Path*> 172.16.0.2/32 172.16.3.1 i

3.1

4.2

4.12.1


MSDP Peers router B


Who is the iBGP peer adverting this route,In our example 172.16.3.1

Is the MSDP == BGP peer

RPF rule when MSDP == internal (m)BGP peer

RPF Failure!Source

A

B

CRP

B

RPF Check Example

146

RPF Check ExampleRPF Check Example

AS1

AS 2

AS3

MSDP/eMBGP mesh-peering

MSDP SA

BGP Table

Network Next Hop Path*> 172.16.0.2/32 172.16.3.1 1 i 172.16.0.2/32 172.16.4.1 3 1 i

3.1

4.2

4.12.1


MSDP Peers router B


RPF rule when MSDP == external (m)BGP peer

Who is the BGP peer adverting this route

BGP Neighbours router B

Neighbor AS Up/Down 172.16.3.1 1 06:06:08 172.16.4.1 3 06:09:06

Source RPF Success!Is the MSDP AS == Last AS in RP route

A

B

CRP

B

147


AS1

AS 2

AS3


MSDP SA

BGP Table

Network Next Hop Path*> 172.16.0.2/32 172.16.3.1 1 i 172.16.0.2/32 172.16.4.1 3 1 i

3.1

4.2

4.12.1


MSDP Peers router B


RPF rule when MSDP == external (m)BGP peer

Who is the BGP peer adverting this route

BGP Neighbours router B

Neighbor AS Up/Down 172.16.3.1 1 06:06:08 172.16.4.1 3 06:09:06

Source RPF Failure!Is the MSDP AS == Last AS in RP route

A

B

CRP

B

148



MSDP SA

BGP Table router B

Network Next Hop Path*> 172.16.0.2/32 172.16.3.1 1 i 172.16.0.2/32 172.16.4.1 3 1 I*> 172.16.4.0/24 172.16.4.1 3 i*> 172.16.3.0/24 172.16.3.1 1 i

MSDP Peers router B


RPF rule when MSDP != (m)BGP peer

AS1

AS 2

AS3

3.1

4.2

4.12.1

ip pim rp-address 172.16.0.2 Source RPF Success!Is the MSDP AS == Last AS in RP route

A

B

CRP

B

149



MSDP SA

BGP Table router B

Network Next Hop Path*> 172.16.0.2/32 172.16.3.1 1 i 172.16.0.2/32 172.16.4.1 3 1 I*> 172.16.4.0/24 172.16.4.1 3 i*> 172.16.3.0/24 172.16.3.1 1 i

MSDP Peers router B


RPF rule when MSDP != (m)BGP peer

AS1

AS 2

AS3

RP

3.1

4.2

4.12.1

ip pim rp-address 172.16.0.2 Source RPF Failure!

Is the MSDP AS == Last AS in RP route

A

B

C

B

150

Cisco MSDP ImplementationCisco MSDP Implementation

• Cisco implementation current with ID:– draft-ietf-msdp-spec-02.txt

• Multiple peer support– Peer with BGP, MBGP, or static peers

• SA caching (off by default)

• Sending and receiving SA-requests

• Sending and receiving SA-responses

151

Cisco MSDP ImplementationCisco MSDP Implementation

• SA input and output filtering

• SA-request input filtering

• Default peer support– So a tail site can MSDP with a backbone provider without

requiring the two to BGP peer

• Triggered join support when creating an (S,G) learned by MSDP

• Mesh groups– Reduces RPF-flooding of SA messages between fully

meshed MSDP peers

152

MSDP ConfigurationMSDP Configuration

• Configure peersip msdp peer <ip-address> [connect-source <i/f>]

• Configure default peerip msdp default-peer <ip-address> [prefix-list acl]

• SA cachingip msdp cache-sa-state [list <acl>]

• Mesh groupsip msdp mesh-group <name> <ip-address>

153

MSDP ConfigurationMSDP Configuration

• Filtering– Can filter SA in/out, groups, with acls or route-maps

• TTL Scopingip msdp ttl-threshold <ip-address> <ttl>

• For more configuration commands see:ftp://ftpeng.cisco.com/ipmulticast/msdp-commands

154

• Use existing (unicast) operation model

MBGP (routing)

• Need interdomain source discovery

MSDP (source discovery)

• Want an explicit join protocol for efficiencyPIM-SM (forwarding)

ISP Requirements to Deploy NowISP Requirements to Deploy Now

155

MSDP Application—Anycast RPMSDP Application—Anycast RP

• draft-ietf-mboned-anycast-rp-05.txt

• Within a domain, deploy more than one RP for the same group range

• Give each RP the same IP address assignment

• Sources and receivers use closest RP

• May be used intra-domain (enterprise) to provide redundancy and RP load sharing

156

MSDP Application—Anycast RPMSDP Application—Anycast RP

• Sources from one RP are known to other RPs using MSDP

• When an RP goes down, sources and receivers are taken to new RP via unicast routing– Fast convergence

157

RP1RP110.0.0.110.0.0.1

RP210.0.0.1

MSDPMSDP

RecRecRecRec

Rec

Rec

SrcSrc

SrcSrc

XX

Anycast RP—ConvergenceAnycast RP—Convergence

158

RP1RP1 RP210.0.0.110.0.0.1 10.0.0.1

Rec

RecRecRecRec

Rec

SrcSrc

Src

XX


159



• IGMP

• PIM

• MSDP

• MBGP

160

MBGP—Multiprotocol BGPMBGP—Multiprotocol BGP

• MBGP overview

• MBGP capability negotiation

• MBGP NLRI exchange

161

MBGP OverviewMBGP Overview

• MBGP: Multiprotocol BGP(aka multicast BGP in multicast networks)– Defined in RFC 2283 (extensions to BGP)

– Can carry different types of routes• Unicast• Multicast

– Both routes carried in same BGP session

– Does not propagate multicast state info

– Same path selection and validation rules• AS-Path, LocalPref, MED, …

162


• New multiprotocol attributes– MP_REACH_NLRI

– MP_UNREACH_NLRI

• MP_REACH_NLRI and MP_UNREACH_NLRI– Address Family Information (AFI) = 1 (IPv4)

• Sub-AFI = 1 (NLRI is used for unicast)• Sub-AFI = 2 (NLRI is used for multicast

RPF check)• Sub-AFI = 3 (NLRI is used for both unicast and multicast RPF

check)

163


• Separate BGP tables maintained– Unicast Routing Information Base (RIB)

– Multicast Routing Information Base (MRIB)

• Unicast RIB (U-RIB)– Contains unicast prefixes for unicast forwarding

– Populated with BGP unicast NLRI• AFI = 1, Sub-AFI = 1 or 3

• Multicast RIB (M-RIB)– Contains unicast prefixes for RPF checking

– Populated with BGP multicast NLRI• AFI = 1, Sub-AFI = 2 or 3

164


• MBGP allows different unicast and multicast topologies and different policies– Same IP address may have different signification

• Unicast routing information• Multicast RPF information

– For same IPv4 address two different NLRI with different next-hops

– Can use existing or new BGP peering topology for multicast

165

MBGP NLRI ExchangeMBGP NLRI Exchange

• BGP/MBGP configuration allows you to:– Define which NLRI type are exchanged

(unicast, multicast, both)

– Set NLRI type through route-maps (redistribution)

– Define policies through standard BGP attributes(for unicast and/or multicast NLRI)

• No redistribution allowed between MBGP and BGP tables– NLRI type can be set with set nlri route-map command

166

MBGP NLRI ExchangeMBGP NLRI Exchange

• MRIB is populated by:– Receiving AFI/SAFI 1/2 MP_REACH_NLRI from

neighbors

– Configured/stored locally by:

network <foo> <foo-mask> [nlri multicast unicast]redistribute <unicast> route-map <map>aggregate-address <foo> <foo-mask> [nlri multicast unicast]neighbor <foo> default-originate [nlri multicast unicast]

• Note: Syntax changes in 12.07T/12.1 forward

167

AS 321AS 123

BGP Session for Unicast and Multicast NLRI

Sender

192.168.100.0/24

192.192.25.0/24

Receiver

MBGP — NLRI InformationMBGP — NLRI Information

.1 .2

192.168.10.0/24 router bgp 321 neighbor 192.168.100.1 remote-as 123 nlri unicast multicastnlri unicast multicast network 192.192.25.0 255.255.255.0 nlri unicast multicastnlri unicast multicastno auto-summary

Congruent Topologies

168

NLRI: 192.192.25/24 AS_PATH: 321MED:Next-Hop: 192.168.100.2...

Unicast Information

Multicast Information

MP_REACH_NLRI: 192.192.25/24AFI: 1, Sub-AFI: 2 (multicast) AS_PATH: 321MED:Next-Hop: 192.168.100.2...

Routing Update


Congruent TopologiesAS 321

AS 123BGP Session for Unicast and

Multicast NLRI

Sender

192.168.100.0/24

192.192.25.0/24

Receiver

.1 .2

192.168.10.0/24

169

AS 321AS 123

192.192.25.0/24

Sender

192.168.100.0/24

192.168.200.0/24

Unicast Traffic.1

.1

.2

.2

router bgp 321 . . . network 192.192.25.0 nlri unicast multicast neighbor 192.168.100.1 remote-as 123 nlri unicast neighbor 192.168.200.1 remote-as 123 nlri multicast

Multicast Traffic


Incongruent Topologies

170

MBGP — NLRI Information

NLRI: 192.192.25/24 AS_PATH: 321MED:Next-Hop: 192.168.100.2192.168.100.2

NLRI: 192.192.25/24 AS_PATH: 321MED:Next-Hop: 192.168.100.2192.168.100.2

Unicast Information

Routing Update


AS 321AS 123

192.192.25.0/24

Sender

192.168.100.0/24

192.168.200.0/24

Unicast Traffic.1

.1

.2

.2Multicast Traffic

171


MP_REACH_NLRI: 192.192.25/24AFI: 1, Sub-AFI: 2 AS_PATH: 321MED:Next-Hop: 192.168.200.2192.168.200.2

MP_REACH_NLRI: 192.192.25/24AFI: 1, Sub-AFI: 2 AS_PATH: 321MED:Next-Hop: 192.168.200.2192.168.200.2

Multicast Information

Routing Update


AS 321AS 123

192.192.25.0/24

Sender

192.168.100.0/24

192.168.200.0/24

Unicast Traffic.1

.1

.2

.2Multicast Traffic

172



AS 321AS 123

192.192.25.0/24

Sender

192.168.100.0/24

192.168.200.0/24

Unicast Traffic.1

.1

.2

.2Multicast Traffic

Network Next-Hop Path192.192.25.0/24 192.168.100.2 321

Network Next-Hop Path192.192.25.0/24 192.168.200.2 321

Unicast RIB

Multicast RIB

173

Populating the MRIBPopulating the MRIB

• Just to restatenetwork <foo> <foo-mask> [nlri multicast unicast]redistribute <unicast> route-map <map>aggregate-address <foo> <foo-mask> [nlri multicast unicast]neighbor <foo> default-originate [nlri multicast unicast]

174

MBGP—SummaryMBGP—Summary

• Solves part of inter-domain problem– Can exchange multicast routing information

– Uses standard BGP configuration knobs

– Permits separate unicast and multicast topologies if desired

• Still must use PIM to:– Build distribution trees

– Actually forward multicast traffic

– PIM-SM recommended• But there’s still a problem using PIM-SM here… (more on that

later)

175

Midterm ExamMidterm Exam

– ...is used to propagate forwarding state?

PIM-SM - Protocol Independent Multicast-Sparse Mode

– ...maintains routing information for interdomain RPF checking?

MBGP - Multiprotocol Border Gateway Protocol

Which protocol...

– …exchanges active source information between RPs?

MSDP - Multicast Source Discovery Protocol

176

AgendaAgenda




• Troubleshooting

• Futures

• Useful Links

177

Putting it all together..Putting it all together..

• PIM-SM, MBGP, MSDP

• Public multicast peering (MIX)

• Transit topology examples

• Address allocation– GLOP draft-ietf-mboned-static-allocation-00.txt

178

ISP Requirements at the MIXISP Requirements at the MIX

• Current solution: MBGP + PIM-SM + MSDP– Environment

• ISPs run iMBGP and PIM-SM (internally)• ISPs multicast peer at a public interconnect

– Deployment • Border routers run eMBGP• The interfaces on interconnect run PIM-SM• RPs’ MSDP peering is fully meshed• All peers set a common distance for eMBGP

179

ISP BPublic

InterconnectISP A

ISP C AS 10888

RPRP

RP RP

eMBGP

iMBGPiMBGP

iMBGPiMBGP

PIM-SM

PIM-SM PIM-SM

Peering Solution: MBGP + PIM-SM +MSDP

ISP Requirements at the MIXISP Requirements at the MIX

Redistribute old MBONEDVMRP routes into MBGP

180

Multicast Transit Design ObjectivesMulticast Transit Design Objectives

• PIM Border Constraints– Confine registers within domain

– Confine local groups

– Confine RP announcements

– Control SA advertisements via MSDP

• Border RPF check– RPF check against unicast routes to multicast sources

• MSDP RPF check– RPF check toward RP in received SAs

181

Recommended MSDP SA FilterRecommended MSDP SA Filter

! domain-local applicationsaccess-list 111 deny ip any host 224.0.2.2 ! access-list 111 deny ip any host 224.0.1.3 ! Rwhodaccess-list 111 deny ip any host 224.0.1.24 ! Microsoft-ds access-list 111 deny ip any host 224.0.1.22 ! SVRLOCaccess-list 111 deny ip any host 224.0.1.2 ! SGI-Dogfightaccess-list 111 deny ip any host 224.0.1.35 ! SVRLOC-DAaccess-list 111 deny ip any host 224.0.1.60 ! hp-device-disc! auto-rp groupsaccess-list 111 deny ip any host 224.0.1.39 access-list 111 deny ip any host 224.0.1.40! scoped groupsaccess-list 111 deny ip any 239.0.0.0 0.255.255.255! loopback, private addresses (RFC 1918)access-list 111 deny ip 10.0.0.0 0.255.255.255 anyaccess-list 111 deny ip 127.0.0.0 0.255.255.255 anyaccess-list 111 deny ip 172.16.0.0 0.15.255.255 anyaccess-list 111 deny ip 192.168.0.0 0.0.255.255 anyaccess-list 111 permit ip any any

ftp://ftp-eng.cisco.com/ipmulticast/msdp-sa-filter.txt

182

Multicast Boundary FilterMulticast Boundary Filter

!deny auto-rp groupsaccess-list 1 deny 224.0.1.40access-list 1 deny 224.0.1.39!deny scoped groupsaccess-list 1 deny 239.0.0.0 0.255.255.255!permit the rest of 224/4access-list 1 permit 224.0.0.0 15.255.255.255

Minimum RecommendedMinimum Recommended

183

192.168.100.0/24

Receiver

Tail-site Customer Transit AS109

RP

PIM Border Constraints

pos0/0 1.1.1.1 pos0/0 1.1.1.2

ip pim send-rp-announce Loopback0 scope 255ip pim send-rp-discovery Loopback0 scope 255

int pos0/0 ip pim sparse-dense-mode

int pos0/0 ip pim sparse-dense-mode

Single-Homed, ISP RP, Non-MBGPSingle-Homed, ISP RP, Non-MBGP

184


Checking PIM Border (RP mapping)

192.168.100.0/24

Receiver


RPpos0/0 1.1.1.1 pos0/0 1.1.1.2

tail-gw#show ip pim rp mappingPIM Group-to-RP Mappings

Group(s) 224.0.0.0/4 RP 3.3.3.7 (loopback.transit.net), v2v1 Info source: 1.1.1.2 (tail.transit.net), via Auto-RP Uptime: 21:57:41, expires: 00:02:08

185


Checking PIM Border (RP mapping)

192.168.100.0/24

Receiver


RPpos0/0 1.1.1.1 pos0/0 1.1.1.2

Transit-tail#show ip pim rp mappingPIM Group-to-RP MappingsThis system is an RP (Auto-RP)This system is an RP-mapping agent

Group(s) 224.0.0.0/4 RP 3.3.3.7 (loopback.transit.net), v2v1 Info source: 3.3.3.7 (loopback.transit.net), via Auto-RP Uptime: 22:08:47, expires: 00:02:14

186

192.168.100.0/24

Receiver


RP

Border RPF Check

pos0/0 1.1.1.1 pos0/0 1.1.1.2

ip route 192.168.100.0 255.255.255.0 1.1.1.1

router bgp 109 ... network 192.168.100.0 nlri unicast multicast

ip route 0.0.0.0 0.0.0.0 1.1.1.2


187

192.168.100.0/24

Receiver


RP

MSDP RPF Check

pos0/0 1.1.1.1 pos0/0 1.1.1.2

- no RP / no MSDP


- no downstream RP - no downstream MSDP peering

188

192.168.100.0/24

Receiver


RP


pos0/0 1.1.1.1 pos0/0 1.1.1.2

int pos0/0 ip pim sparse-mode ip pim bsr-border ip multicast boundary 1

ip msdp sa-filter out 1.1.1.2 111ip msdp sa-filter in 1.1.1.2 111

Single-Homed, Customer RP, Non-MBGPSingle-Homed, Customer RP, Non-MBGP

Note: Access-list 111 = Recommended SA Filter

189

192.168.100.0/24

Receiver


RP


pos0/0 1.1.1.1 pos0/0 1.1.1.2





190

192.168.100.0/24

Receiver


RP

Border RPF Check

pos0/0 1.1.1.1 pos0/0 1.1.1.2

ip route 192.168.100.0 255.255.255.0 1.1.1.1

router bgp 109 ... network 192.168.100.0 nlri unicast multicast

ip route 0.0.0.0 0.0.0.0 1.1.1.2


191

192.168.100.0/24

Receiver


RP

MSDP RPF Check

pos0/0 1.1.1.1 pos0/0 1.1.1.2

ip msdp peer 1.1.1.1 connect-source pos0/0



192

192.168.100.0/24

Receiver


RP


pos0/0 1.1.1.1 pos0/0 1.1.1.2



Single-Homed, Customer RP, MBGPSingle-Homed, Customer RP, MBGP


193

192.168.100.0/24

Receiver


RP


pos0/0 1.1.1.1 pos0/0 1.1.1.2





194

192.168.100.0/24

Receiver


RP

Border RPF Check

pos0/0 1.1.1.1 pos0/0 1.1.1.2


router bgp 109 neighbor 1.1.1.1 remote-as 100 nlri unicast multicast neighbor 1.1.1.1 update-source pos 0/0

router bgp 100 network 192.168.100.0 nlri unicast multicast neighbor 1.1.1.2 remote-as 109 nlri unicast multicast neighbor 1.1.1.2 update-source pos0/0

195

192.168.100.0/24

Receiver


RP

MSDP RPF Check

pos0/0 1.1.1.1 pos0/0 1.1.1.2




196

Which Mode—Sparse or DenseWhich Mode—Sparse or Dense

• Sparse mode– Must configure a Rendezvous Point (RP)

• Statically (on every Router)• Using Auto-RP (Routers learn RP automatically)• Using BSR (Routers learn RP automatically)

– Very efficient• Uses Explicit Join model• Traffic only flows to where it’s needed

– Separate control and data planes• Router state only created along flow paths• Deterministic topological behavior

– Scales better than dense mode• Works for bothboth sparsely or densely populated networks

197

CONCLUSIONCONCLUSIONVirtually all production networks should

be configured to run in Sparse mode!

Which Mode—Sparse or DenseWhich Mode—Sparse or Dense

198

RP PlacementRP Placement

• Q: “Where do I put the RP?”– A: “Generally speaking, it’s not critical”

• SPT’s are normally used by default– RP is a place for source and receivers to meet– Traffic does not normally flow through the RP– RP is therefore not a bottleneck

• Exception: SPT-Threshold = Infinity– Traffic stays on the shared tree– RP couldcould become a bottleneck

199

Static RP’sStatic RP’s

• Hard-coded RP address– When used, must be configured on every router

– All routers must have the same RP address

– RP fail-over not possible• Exception: If Anycast RPs are used.

• Commandip pim rp-address <address> [group-list <acl>] [override]

– Optional group list specifies group range• Default: Range = 224.0.0.0/4 (Includes Auto-RP Groups!!!!)(Includes Auto-RP Groups!!!!)

– Override keyword “overrides” Auto-RP information• Default: Auto-RP learned info takes precedence

200

Auto-RP OverviewAuto-RP Overview

• All routers automatically learn RP address– No configuration necessary except on:

• Candidate RPs• Mapping Agents

• Makes use of Multicast to distribute info– Two specially IANA assigned Groups used

• Cisco-Announce - 224.0.1.39• Cisco-Discovery - 224.0.1.40

– Typically Dense mode is used forward these groups

• Permits backup RP’s to be configured

• Can be used with Admin-Scoping

201

Auto-RP FundamentalsAuto-RP Fundamentals

• Candidate RPs– Configured via global config command

ip pim send-rp-announce <intfc> scope <ttl> [group-list acl]

– Multicast RP-Announcement messages• Sent to Cisco-Announce (224.0.1.39) group• Sent every rp-announce-interval (default: 60 sec)

– RP-Announcements contain:• Group Range (default = 224.0.0.0/4)• Candidate’s RP address• Holdtime = 3 x <rp-announce-interval>

202


• Mapping agents– Configured via global config command

ip pim send-rp-discovery scope <ttl>

– Receive RP-Announcements• Select highest C-RP IP addr as RP for group range• Stored in Group-to-RP Mapping Cache with holdtimes

– Multicast RP-Discovery messages• Sent to Cisco-Discovery (224.0.1.40) group• Sent every 60 seconds or when changes detected

– RP-Discovery messages contain:• Contents of MA’s Group-to-RP Mapping Cache

203


• All Cisco routers– Join Cisco-Discovery (224.0.1.40) group

• Automatic • No configuration necessary

– Receive RP-Discovery messages• Stored in local Group-to-RP Mapping Cache• Information used to determine RP for group range

204

Auto-RP—From 10,000 FeetAuto-RP—From 10,000 Feet

Announce Announce

Ann

ounc

eA

nnou

nce

Announce Announce

Ann

ounc

eA

nnou

nce

Announce

RP-Announcements multicast to theCisco Announce (224.0.1.39) group

AA

CC DDC-RP1.1.1.1

C-RP2.2.2.2

BB

MA MA

205

CC DDC-RP1.1.1.1

C-RP2.2.2.2

Auto-RP—From 10,000 FeetAuto-RP—From 10,000 Feet

Discovery

Discovery

Dis

cove

ry

Dis

cove

ry

Discovery

Discovery

Dis

cove

ry

Dis

cove

ry

Discovery

RP-Discoveries multicast to theCisco Discovery (224.0.1.40) group

AA BB

MA MA

206

BSR OverviewBSR Overview

• A single Bootstrap Router (BSR) is elected– Multiple Candidate BSR’s (C-BSR) can be configured

• Provides backup in case currently elected BSR fails

– C-RP’s send C-RP announcements to the BSR• C-RP announcements are sent via unicast

• BSR stores ALL C-RP announcements in the “RP-set”

– BSR periodically sends BSR messages to all routers• BSR Messages contain entire RP-set and IP address of BSR

• Messages are flooded hop-by-hop throughout the network away from the BSR

– All routers select the RP from the RP-set• All routers use the same selection algorithm; select same RP

• BSR cannot cannot be used with Admin-Scoping

207

BSR FundamentalsBSR Fundamentals

• Candidate RPs– Configured via global config command

– ip pim rp-candidate <intfc> [group-list acl]

– Unicast PIMv2 C-RP messages to BSR• Learns IP address of BSR from BSR messages• Sent every rp-announce-interval (default: 60 sec)

– C-RP messages contain:• Group Range (default = 224.0.0.0/4)• Candidate’s RP address• Holdtime = 3 x <rp-announce-interval>

208


• Bootstrap router (BSR)– Receive C-RP messages

• Accepts and stores ALL C-RP messages• Stored in Group-to-RP Mapping Cache w/holdtimes

– Originates BSR messages• Multicast to All-PIM-Routers (224.0.0.13) group

– (Sent with a TTL = 1)• Sent out all interfaces. Propagate hop-by-hop• Sent every 60 seconds or when changes detected

– BSR messages contain:• Contents of BSR’s Group-to-RP Mapping Cache• IP Address of active BSR

209


• Candidate bootstrap router (C-BSR)– Configured via global config command

ip pim bsr-candidate <intfc> <hash-length> [priority <pri>]

– <intfc>» Determines IP address

– <hash-length> » Sets RP selection hash mask length

– <pri> » Sets the C-BSR priority (default = 0)

– C-BSR with highest priority elected BSR– C-BSR IP address used as tie-breaker

» (Highest IP address wins)– The active BSR may be preempted

» New router w/higher BSR priority forces new election

210


• All PIMv2 routers– Receive BSR messages

• Stored in local Group-to-RP Mapping Cache• Information used to determine active BSR address

– Selects RP using Hash algorithm• Selected from local Group-to-RP Mapping Cache• All routers select same RP using same algorithm• Permits RP-load balancing across group range

211

PIMv2 Sparse Mode

PIMv2 Sparse Mode

C-RP C-RP

D

E

F

G

A

BSR—From 10,000 feetBSR—From 10,000 feet

BS

R M

sgs

BSR MsgsBSR Msgs

BS

R M

sgs

C-RP Advert

isemen

t

(unicast)

C-RP Advertisement

(unicast)

BSR Msgs Flooded Hop-by-Hop

B C

BSRBSR

212

Auto-RP vs BSRAuto-RP vs BSR

• Auto-RP– Easy to configure

– Supports Admin. Scoped Zones

– Works in either PIMv1 or PIMv2 Cisco networks

– Cisco proprietary

• BSR– Easy to configure

– Does notnot support Admin. Scoped Zones

– Non-proprietary (PIMv2 networks only)

213

Anycast RP—OverviewAnycast RP—Overview

• Uses single statically defined RP address– Two or more routers have same RP address

• RP address defined as a Loopback Interface.• Loopback address advertised as a Host route.

– Senders & Receivers Join/Register with closest RP• Closest RP determined from the unicast routing table.

• MSDP session(s) run between all RPs– Informs RPs of sources in other parts of network

– RPs join SPT to active sources as necessary

214

RP1RP110.0.0.110.0.0.1

RP210.0.0.1

MSDPMSDP

RecRecRecRec

Rec

Rec

SrcSrc

SrcSrc

XX


215

RP1RP1 RP210.0.0.110.0.0.1 10.0.0.1

Rec

RecRecRecRec

Rec

SrcSrc

Src

XX


216

PIM Configuration StepsPIM Configuration Steps

• Enable Multicast Routing on every every router

• Configure every every interface for PIM• Use Sparse-Dense Mode (to support Auto-RP)

• Configure the RP (if using Sparse Mode)– Static RP addressing

• RP address must be configured on every router

– Using Auto-RP or BSR• Configure certain routers as Candidate RP(s)• All other routers automatically learn elected RP

217

PIM Sparse Mode

PIM Sparse Mode

RP/Mapping AgentC D

A B

On every router: ip multicast-routingip pim accept-RP Auto-RP

On every interface: ip pim sparse-dense-mode

On routers B and C: ip pim send-rp-announce loopback0 scope <ttl>ip pim send-rp-discovery loopback0 scope <ttl>

RP/Mapping Agent

Fool-Proof Multicast ConfigurationFool-Proof Multicast Configuration

218

We’ll just use the spare 56K line for the IP Multicast traffic and not the T1.

no ip pim dense-mode ip pim dense-mode

Classic Partial Multicast Cloud Mistake

T1 56K

src

rcvrNetworkEngineer

XX

RPF Failure!!!!!RPF Failure!!!!!

219

JUST DO IT!JUST DO IT!Enable multicast on ALLALL interfaces in ALLALL routers in a given network. Failure to do

so will require complex (and typically unnecessary) Multicast Traffic Engineering.

Beginner’s Guide to IP MulticastBeginner’s Guide to IP Multicast

220

AgendaAgenda




• Troubleshooting

• Futures

• Useful Links

221

Debugging and TroubleshootingDebugging and Troubleshooting

• Monitoring Tools– sdr_monitor

• Kamil Sarac and Kevin Almeroth - UCSB• http://www.cs.ucsb.edu/~ksarac/sdr-desc.html• Several sites on Abilene and vBNS

– mlisten• http://www.cc.gatech.edu/computing/Telecomm/mbone/

– Abilene Core Node Router Proxy• http://hydra.uits.iu.edu/~abilene/proxy/

222


• Multicast Looking Glass– Written by NLANR Engineering Services

– Based on DIGEX Looking Glass

– Queries Pittsburgh GigaPoP multicast border router for multicast information

– http://www.ncne.nlanr.net/tools/mlg2.html

223


• Mtrace– No longer gives coherent stats

– Won’t even traverse some routers

– Basically useless

• Multicast Debugging Handbook– draft-ietf-mboned-mdh-02.txt

225

>show ip sdrshow ip sdr

SDR Cache - 67 entries

2/5 ASSIST J Kerr Repeat

3/4 LAN Systems - NT & SMS in Labs

4J KRVM Radio

ABONE Discussion

BGMP/MASC discussion

CANARIE 5th Annual Advanced Networks Workshop(MPEG1)

dslab-test

ECG - Tunnel Test from UB

GT test

High Bandwidth Bird (HBB)

iBAND3 Keynotes [MP3] at Stardust.com

IMJ -- Channel 1

IMJ -- Channel 2

Korea Radio Broadcasting from SNU

...

226

>show ip sdr detail>show ip sdr detailSDR Cache - 68 entries

Session Name: BGMP/MASC discussion

Description: BGMP/MASC discussion

Group: 0.0.0.0, ttl: 0, Contiguous allocation: 1

Lifetime: from 12:30:00 EDT May 31 1999 until 19:50:00 EDT Jun 9 2000

Uptime: 12:17:02, Last Heard: 11:27:03

Announcement source: 128.9.160.100, destination: 224.2.127.254

Created by: pavlin 3136737610 3136737920 IN IP4 128.9.160.100

Phone number: Pavlin Radoslavov (USC/ISI) +1 310 822 1511 (ext. 8125)

Email: Pavlin Radoslavov (USC/ISI) <[email protected]>

URL: http://netweb.usc.edu/bgmp/

Media: audio 17396 RTP/AVP 0

Media group: 224.2.134.153, ttl: 127

Attribute: ptime:40

Media: whiteboard 48173 udp wb

Media group: 224.2.188.133, ttl: 127

Media: text 56770 udp nt

Media group: 224.2.168.204, ttl: 127

227

>show ip sdr "NASA TV - Broadcast from NASA HQ"

SDR Cache - 68 entries

Session Name: NASA TV - Broadcast from NASA HQ

Description: NASA TV Multicasting from NASA HQ

Group: 0.0.0.0, ttl: 0, Contiguous allocation: 1

Lifetime: from 12:36:16 EDT Jun 11 1999 until 11:36:16 EST Dec 11 1999

Uptime: 1d17h, Last Heard: 18:21:10

Announcement source: 131.182.10.250, destination: 224.2.127.254

Created by: ellery 3132060082 3138107776 IN IP4 131.182.10.250

Phone number: +202 651 8512

Email: [email protected] (Ellery D. Coleman)

URL: http://www.nasa.gov/ntv

Media: audio 23748 RTP/AVP 0

Media group: 224.2.203.38, ttl: 127

Media: video 60068 RTP/AVP 31

Media group: 224.2.203.37, ttl: 127

Attribute: framerate:9

Attribute: quality:8

Attribute: grayed:0

228

>show ip bgp neighbors 192.88.115.113

BGP neighbor is 192.88.115.113, remote AS 145, external link

Index 2, Offset 0, Mask 0x4

NEXT_HOP is always this router

BGP version 4, remote router ID 204.147.128.139

BGP state = Established, table version = 2, up for 05:54:44

Last read 00:00:05, last send 00:00:07

Hold time 90, keepalive interval 30 seconds

Neighbor NLRI negotiation:

Configured for unicast and multicast routes

Peer negotiated unicast and multicast routes

Exchanging unicast and multicast routes

...

Number of unicast/multicast prefixes received 0/6773

...

229

>show ip mbgp neigh 192.88.115.113 adv

Network Next Hop Metric LocPrf Weight Path

*> 128.182.0.0 0.0.0.0 0 32768 i

*> 192.88.115.64/24 0.0.0.0 0 32768 i

230

AgendaAgenda




• Troubleshooting

• Futures

• Useful Links

231

FuturesFutures

• PIM modes designed for specific scalings and applications– Bidir-PIM

– Single Source Multicast (SSM)

232

Bidir PIMBidir PIM

• Designed for many to many multicast groups

• Builds a single (*,G) shared tree which all sources use

• Relieves the router from having to keep state for each and every source

233

SSMSSM

• Designed to allow receivers to specify the single source which they wish to receive traffic from, such as when viewing a broadcast from a single provider

• Requires IGMPv3 so that receivers can tell the first hop router which source they want

• RP is not used

• Requires an out of band method to discover the proper source (e.g. a web pag or email

234

AgendaAgenda




• Troubleshooting

• Futures

• Useful Links

235

Useful LinksUseful Links

• Multicast Documentation (FAQ and Tools): http://www.ncne.nlanr.net/faq/multicast.html

• Cisco IOS Documentation • Cisco IP Multicast: ftp://ftp-eng.cisco.com/ipmulticast/• Introduction to Multicast Routing:

http://www.3com.com/nsc/501303.html• Send mail to [email protected]

connecting to the ip multicast world

Documents