CCNP-I-BSCI_Module_7_Lesson_3_Multicast_Routing_Protocols

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IP Multicasting: Multicast Routing Protocols

BSCI Module 7 Lesson 3

BSCI Module 7 Lesson 3

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Objectives Describe a multicast network in terms of the IP multicast routing protocols and processes used over various segments. Describe multicast distribution trees including source trees and shared trees. Describe the (S,G) and (*,G) multicast distribution trees entry formats. Explain IP multicast routing. Identify the characteristics of each of the PIM modes.

Describe the operation of PIM-DM, PIM-SM, and PIM sparse-dense modes.BSCI Module 7 Lesson 3 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public

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Multicast Distribution Trees

BSCI Module 7 Lesson 3

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Multicast Protocol BasicsTypes of multicast distribution trees: Source distribution trees; also called shortest path trees (SPTs) Shared distribution trees; rooted at a meeting point in the networkA core router serves as a rendezvous point (RP)

BSCI Module 7 Lesson 3

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Multicast Distribution TreesShortest Path or Source Distribution TreeSource 1 Notation: (S, G) S = Source G = Group Source 2A B D F

C

E

Receiver 1BSCI Module 7 Lesson 3

Receiver 2

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Multicast Distribution TreesShortest Path or Source Distribution TreeSource 1 Notation: (S, G) S = Source G = Group Source 2A B D F

C

E

Receiver 1BSCI Module 7 Lesson 3

Receiver 2

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Multicast Distribution TreesShared Distribution TreeNotation: (*, G) * = All Sources G = Group

A

B

D (RP)

F

C

E

(RP)

PIM Rendezvous Point

Shared Tree

Receiver 1BSCI Module 7 Lesson 3

Receiver 2

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Multicast Distribution TreesShared Distribution TreeSource 1 Notation: (*, G) * = All Sources G = Group Source 2A B

D (RP)

F

C

E

(RP)

PIM Rendezvous Point

Shared TreeSource Tree Receiver 1BSCI Module 7 Lesson 3

Receiver 2

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Multicast Distribution Tree Identification(S,G) entries For this particular source sending to this particular group Traffic is forwarded through the shortest path from the source

(*,G) entries For any (*) source sending to this group Traffic is forwarded through a meeting point for this group

BSCI Module 7 Lesson 3

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Multicast Distribution TreesCharacteristics of Distribution Trees

Source or Shortest Path trees Uses more memory but optimal paths from source to all receivers; minimizes delay

Shared trees Uses less memory but sub-optimal paths from source to all receivers; may introduce extra delay

BSCI Module 7 Lesson

3

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Self Check1. What is an advantage of Shortest Path Trees compared to Shared Trees?

2. What does multicast use to make it’s forwarding decisions?3. In the STP notation (S,G), what do each of the characters represent? 4. What is the root of the shared tree called? 5. Compare Shared Distribution trees and SPT trees in terms of router memory and packet delivery delay.

BSCI Module 7 Lesson 3

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Multicast Routing

BSCI Module 7 Lesson 3

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Protocols for IP Multicast Routing

PIM is used between routers so that they can track which multicast packets to forward to each other and to their directly connected LANs.BSCI Module 7 Lesson 3 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public

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Protocol-Independent Multicast (PIM) PIM maintains the current IP multicast service mode of receiver-initiated membership. PIM is not dependent on a specific unicast routing protocol. With PIM, routers maintain forwarding tables to forward multicast datagrams. PIM can operate in dense mode or sparse mode.Dense mode protocols flood multicast traffic to all parts of the network and prune the flows where there are no receivers using a periodic flood-and-prune mechanism. Sparse mode protocols use an explicit join mechanism where distribution trees are built on demand by explicit tree join messages sent by routers that have directly connected receivers.BSCI Module 7 Lesson 3 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public

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Multicast Tree CreationPIM Join/Prune Control Messages Used to create/remove Distribution Trees

Shortest Path trees PIM control messages are sent toward the Source Shared trees PIM control messages are sent toward RP

BSCI Module 7 Lesson 3

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Multicast ForwardingMulticast routing operation is the opposite of unicast routing.

Unicast routing is concerned with where the packet is going. Multicast routing is concerned with where the packet comes from. Multicast routing uses Reverse Path Forwarding (RPF) t …… 此处隐藏：3251字，全部文档内容请下载后查看。喜欢就下载吧 ……