IP Networking Part 6‐gAn Introduction to

IP MulticastIP Multicast “A webinar to help you prepare 

for the CBNE™ Certification” 

Wayne M. Pecena, CPBE, CBNE

Texas A&M Information TechnologyEducational Broadcast Services

IP Networking Part 6‐ An Introduction to IP Multicast  “A webinar to help you prepare for the CBNE™ Certification” 

Advertised Presentation Scope:

IP Multicast is a unique aspect of IP Networking technology that provides “One-to-Many” communications between a source IP host and numerous subscriber IPMany communications between a source IP host and numerous subscriber IP hosts. The use of IP Multicast for delivery of real-time media content often finds widespread use in the broadcast facility.

Thi bi ill f d t di M lti t t i l th dd iThis webinar will focus upon understanding Multicast terminology, the addressing utilized, and the basics of switching and routing in a multicast IP network. Practical implementation examples to deliver AoIP and IPTV content will be utilized to illustrate the theoretical concepts presented.p p

My Goals & Deliverables for This Afternoon:

Provide an Awareness of IP Multicast Terminology & Concepts on IPv4‐ Provide an Awareness of IP Multicast Terminology & Concepts on IPv4 Networks

‐ Provide an Understanding of IP Multicast Implementation ‐ Provide Reference Material & Resources to Obtain Further KnowledgeProvide Reference Material & Resources  to Obtain Further Knowledge

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Agenda

• Introduction to IP Multicast Terminology

• The Multicast Group• The Multicast Group

• Multicast Addressing 

– Layer 2 Address

– Class D Layer 3 Address

• Multicast Switching & Routing

• Broadcast Deployment Examples 

– AoIP Systems

– IPTV Systems

• Acronym GlossaryAcronym Glossary

• Reference Documents

• Takeaway Summary – Q&A

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Multicast IntroductionMulticast Introduction• IP Networking is Founded on an “Unicast” Model

– One Send Host to One Receive Host

• Or the “Broadcast” Model– One Send Host to All Other Hosts on the SubnetOne Send Host to All Other Hosts on the Subnet

Unicast IP Packet(s)

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MulticastMulticast

• Multicast Adds a 3rd Packet Distribution Approachpp

– One Send Host to A Group of Receive Hosts on the Subnet

A Host Must JoinA Multicast GroupTo Receive MulticastPackets

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Types of IP Packets on an IPv4 NetworkTypes of IP Packets on an IPv4 Network

• Unicast– One Send Host Communicates With One Receive Host

• Broadcast– One Send Host Communicates With ALL Hosts on the Subnet

• Multicast– One Send Host Communicates With A Group of Specific Hosts

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UnicastUnicast

Router BSwitch 2

Router ASwitch 1

Switch 3

Router C Switch 4

Switch 5

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Switch 5

BroadcastBroadcast

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MulticastMulticast

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Why IP Multicast?Why IP Multicast?• IP Multicast is a Bandwidth Conserving Technology

P id Effi i C l f N k T ffi• Provides Efficient Control of Network Traffic

• Server & CPU Load Decrease

• Eliminates Network Traffic Redundancy• Eliminates Network Traffic Redundancy

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Number of Clients

Key Terminology To Be Aware Of:Key Terminology To Be Aware Of:

• Multicast Groups

• Class D IP Address Space

• Internet Group Management Protocol – IGMP

• Multicast Distribution Tree

• Protocol Independent Multicast – PIM

• Reverse Path Forwarding – RPF

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IP Multicast AddressingIP Multicast Addressing

• Layer 2 Addressing (physical address)y g (p y )– 23 Bits of 48 Bit MAC Address Reserved for Multicast

– By Default: A Layer 2 Switch Will Forward Multicast Packets Out All Ports (except origin port)Ports (except origin port)

– To Eliminate “Flooding” – IGMP Snooping is Utilized

IP G Add i ( i t l dd )• IP Group Addressing (virtual address)– 28 Bits of 32 Bit IP Address Reserved for Multicast

– Class D IP Address Range Reserved for Multicast• 224.0.0.0 to 239.255.255.255

– Layer 2 Multicast Address Derived From Layer 3 IP Address

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IP Group AddressingIP Group Addressing

• Multicast Utilizes “Class D” Reserved IP Address Spacep– 224.0.0.0 to 239.255.255.255

• Ranges Reserved Within Class D Address Space:/– 224.0.0.0 to 224.0.0.255  Local Multicast / Routing Protocol Use

– 224.0.1.0 to 238.255.255.255  Public Use (Globally Scoped)

– 239.0.0.0 to 239.255.255.255 Private Use (Limited Scope)

• Common Multicast Addresses:– 224.0.0.1 All Hosts on Subnet

224 0 0 2 All R t S b t– 224.0.0.2 All Routers on Subnet

– 224.0.0.5 All OSPF Routers

– 224.0.0.22 IGMP Traffic

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Deriving a Multicast Layer 2 AddressDeriving a Multicast Layer 2 Address

The OUI of a Multicast MAC Address is Always “01:00:5e”The Last 3 Hex Digits of the MAC Address Are Calculated Off theThe Last 3 Hex Digits of the MAC Address Are Calculated Off the

Last 23 Bits of the IP Address

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Internet Group Management Protocol“ ”“IGMP”

• A Multicast Group is Identified by a Multicast Address.p y

• IGMP is the Protocol That Allows a Multicast Receive Client (Host) to Send a Request to Join a Multicast Group.

• Three Versions of IGMP Exist:– IGMPv1 (RFC 1112)

– IGMPv2 (RFC 2236)IGMPv2 (RFC 2236)

– IGMPv3 (RFC 3376)

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IGMP Message TypesIGMP Message Types• Membership “Query”

– A Request to Identify Members of a Multicast Group

• Membership “Report”– List of Members of a Multicast Group

L G• Leave Group– Terminates Multicast Group Membership (Disconnect)

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IGMP in More DetailIGMP in More Detail• Multicast Works by Having a Multicast Source Send Packets 

to a Specific Group of Host Clients That Belong to theto a Specific Group of Host Clients That Belong to the Multicast Group.

• The Multicast Group is Assigned a Specific Multicast Address.

• IGMP Provides for Host Clients to Send a “Join” Request to a Multicast Enabled Router.

• IGMP “Snooping” Allows a Layer 2 Switch to “Learn” the• IGMP “Snooping” Allows a Layer 2 Switch to  Learn  the Multicast MAC Address of Multicast Groups.

• IGMP Snooping “Listens” to IGMP Membership Reports and p g p pBuilds a Multicast MAC Entry in the Switch Table.

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IP Multicast Distribution TreeIP Multicast Distribution Tree

• An IP Multicast Distribution Tree is a Path Structure From a Multicast Source to a Multicast DestinationMulticast Source to a Multicast Destination.

“Trim” or“Prune” the Tree

Single Source Tree“Graft”

The Tree

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Protocol Independent MulticastPIM

• PIM is Focused on Getting Multicast Packets to the Desired Destination 

• PIM Creates the Multicast Tree & “Trims” the Tree

• 3‐Types of PIM:

– PIM Dense ModePIM Dense Mode

– PIM Sparse Mode

– PIM Sparse‐Dense Mode (PIM‐SM‐DM “Cisco Proprietary”)

iff d ?• Key Difference Between PIM Modes?

– How The Distribution Tree is Created

• Which is Best?

– Dense Mode Used in Large Networks – Quick Tree Creation

– Sparse Mode Used in Smaller Networks – More Efficient Bandwidth Use

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PIM Dense Mode“ ”“PIM‐DM”

• All Segments of the Multicast Tree Are “Flooded”. 

• Branches Are “Pruned” if Multicast Traffic is Not needed.

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PIM Sparse Mode“ ”“PIM‐SM”

• Multicast Traffic is NOT Flooded.

• A “Rendezvous Point” is Designated.

• All Multicast Sources & Clients Register With the Rendezvous Point.

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Multicast Forwarding (Routing)RFC 3704

• Unicast Routing Only Looks at the Destination Address

• Multicast Traffic is Forwarded Away From the Source Host or Downstream• Multicast Traffic is Forwarded Away From the Source Host or Downstream

• Reverse Path Forwarding (RPF) is Used to Prevent Loops

• A Router Only Forwards Traffic Received on an Upstream Interface 

• RPF Check Used to Determine if an Interface is Valid• RPF Check Used to Determine if an Interface is Valid

cast

Packe

t

Multicast Packet

Multica

et

Multica

st Pac

ket

Multicast Packet X Discarded

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What About Multicast on an IPv6 Network?What About Multicast on an IPv6 Network?

• Multicast is Inherent to IPv6!

• But, You Still Must:– Build the Distribution Tree

– Provide Routing Info

• Multicast IPv6 Address Format Defined by RFC 3513– FF00::/8 address prefix format/ p

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Practical Applications of IP MulticastPractical Applications of IP Multicast

• Typical Applications:Typical Applications:– Video Conferencing

– Digital Signage / Corporate Communications

– Stock Quote Distribution

– Distance Learning

• Common Implementation Examples:– AoIP

– IPTV

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AoIP ImplementationAoIP Implementation

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Courtesy: AXIA - A Telos Company

AXIA “Livewire” System HeartAXIA  Livewire  System Heart

Adequate Hardware Platform is a Given. Non-Blocking Backplane.

Adequate Frame Forwarding Rate

The Key Is the Software!Such As:

Multilayer Software Image (SMI) – Layer 2/3y g ( ) yPriority Queuing

Multicast Feature SupportIGMP Support

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IPTV ImplementationHotel Room TV System

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MulticastMulticastAcronym Glossary

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ReferencesReferenceshttp://www.cisco.com/en/US/docs/ios/solutions_docs/ip_multicast/White_papers/mcst_ovr.html

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Additional IETF ReferencesInternet Engineering Task ForceInternet Engineering Task Force

• RFC 1112 Host Extension for IP Multicasting

• RFC 1918 Address Allocation for Private InternetsRFC 1918 Address Allocation for Private Internets

• RFC 2362 PIM ‐ SM

• RFC 2365 Administratively Scoped IP Multicast

• RFC 2770 GLOP Addressing

• RFC 2283 Multiprotocol Extensions for BGP‐4

i tf30

www.ietf.org

Takeaway SummaryTakeaway Summary• IP Multicast Focused on “One to Many” Communications

• IETF RFC’s Define IP Multicast Implementation• IETF RFC s Define IP Multicast Implementation

• Class D IP Address Space is “Reserved” for IP Multicast

• IP Multicast Limited to “UDP” Packet Delivery

• Multicast “Reverse Path” Routing is the Key to Implementation

• IPv6 Natively Incorporates IP Multicast

• The “Internet” Does Not Support IP Multicast!

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? Questions ?? Questions ?

Thank You for Attending!

Wayne M. PecenaTexas A&M Universityw‐pecena@tamu.edu979.845.5662

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