MCASTImplementing Cisco MulticastVersion 1.0 Student Guide Copyright 2003, Cisco Systems, Inc. AII rights reserved. Cisco Systems has more than 200 oIIices in the Iollowing countries and regions. Addresses, phone numbers, and Iax numbers are listed on the Cisco Web site at www.cisco.com/go/oIIices.Argentina Australia Austria Belgium Brazil Bulgaria Canada Chile China PRC Colombia Costa Rica Croatia Czech Republic Denmark Dubai, UAE Finland France Germany Greece Hong Kong SAR Hungary India Indonesia Ireland Israel Italy Japan Korea Luxembourg Malaysia Mexico The Netherlands New Zealand Norway Peru Philippines Poland Portugal Puerto Rico Romania Russia Saudi Arabia Scotland Singapore Slovakia Slovenia South AIrica Spain Sweden Switzerland Taiwan Thailand Turkey Ukraine United Kingdom United States Venezuela Vietnam Zimbabwe Copyright 2003, Cisco Systems, Inc. All rights reserved. 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(0203R)Copyright 2003, Cisco Systems, nc. mplementing Cisco Multicast (MCAST) v1.0 iMODULE 1 - COURSE INTRODUCTION 1-1 Overview 1-1 Course Objectives 1-2 Learner Skills and Knowledge 1-9 Learner Responsibilities 1-10 General Administration 1-11 Sources of nformation 1-12 Course Roadmap 1-13 Learner ntroductions 1-16MODULE 2 - IP MULTICAST TECHNOLOGY 2-1 Overview 2-1 Outline 2-1 Objectives 2-2LESSON ONE: IP MULTICAST - BENEFITS AND CAVEATS 2-3LESSON TWO: IP MULTICAST APPLICATION TYPES 2-14LESSON THREE: THE BASIC MODEL OF IP MULTICAST 2-33LESSON FOUR: IP MULTICAST ADDRESSING 2-44LESSON FIVE: MULTICAST SESSIONS - DIRECTORY SERVICES 2-53 Summary 2-65MODULE 3 - IP MULTICAST DISTRIBUTION TREES AND CONTROL PROTOCOLS3-1 Overview 3-1 Outline 3-1 Objectives 3-2LESSON ONE: FUNCTIONS OF MULTICAST-ENABLED NETWORKS 3-3LESSON TWO: MULTICAST DISTRIBUTION TREES AND PROTOCOL TYPES 3-18LESSON THREE: OVERVIEW OF MULTICAST ROUTING PROTOCOLS 3-30LESSON FOUR: REPORTING GROUP MEMBERSHIP 3-87 Summary 3-120MODULE 4 - IP MULTICASTING AT LAYER 2 4-1 Overview 4-1 Outline 4-1 Objectives 4-2ii mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. LESSON ONE: MULTICAST MAC-LAYER ADDRESSES AND SWITCH FORWARDING 4-3LESSON TWO: CONSTRAINING MULTICAST STREAMS ON LAN SWITCH PORTS 4-16 Summary 4-37MODULE 5 - PIM DENSE MODE PROTOCOL 5-1 Overview 5-1 Outline 5-1 Objectives 5-2LESSON ONE: PIM DENSE MODE OVERVIEW 5-3LESSON TWO: PIM DENSE MODE DETAILS 5-22LESSON THREE: PIM DENSE MODE IMPLEMENTATION AND TROUBLESHOOTING5-75 Summary 5-102MODULE 6 - PIM SPARSE MODE PROTOCOL 6-1 Overview 6-1 Outline 6-1 Objectives 6-2LESSON ONE: PIM SPARSE MODE OVERVIEW 6-3LESSON TWO: PIM SPARSE MODE DETAILS 6-26 Summary 6-118MODULE 7: PIM SM IMPLEMENTATION AND VARIANTS OF PIM SM 7-1 Overview 7-1 Outline 7-1 Objectives 7-2LESSON ONE: PIM SPARSE MODE IMPLEMENTATION AND TROUBLESHOOTING 7-3LESSON TWO: BIDIRECTIONAL PIM AND SOURCE SPECIFIC MULTICAST 7-21 Summary 7-67MODULE 8: RELIABLE IP MULTICASTING 8-1 Overview 8-1 Outline 8-1Copyright 2003, Cisco Systems, nc. mplementing Cisco Multicast (MCAST) v1.0 iii Objectives 8-2LESSON ONE: WHAT IS RELIABLE IP MULTICAST? 8-3LESSON TWO: CISCO IOS IMPLEMENTATION OF PGM 8-43 Summary 8-53MODULE 9: IP MULTICASTING IN SWITCHED LAN ENVIRONMENT 9-1 Overview 9-1 Outline 9-1 Objectives 9-2LESSON ONE: CGMP IMPLEMENTATION 9-3LESSON TWO: IGMP SNOOPING IMPLEMENTATION 9-24LESSON THREE: RGMP IMPLEMENTATION 9-36 Summary 9-47MODULE 10 - IP MULTICAST IMPLEMENTATION IN NBMA NETWORKS 10-1 Overview 10-1 Outline 10-1 Objectives 10-2LESSON ONE: PROBLEMS OF RUNNING IP MULTICAST OVER NBMA MEDIA 10-3LESSON TWO: PIM NBMA MODE 10-20 Summary 10-47MODULE 11 - SIMPLE INTRADOMAIN DEPLOYMENT OF IP MULTICAST 11-1 Overview 11-1 Outline 11-1 Objectives 11-2LESSON ONE: MULTICAST APPLICATIONS REQUIREMENTS 11-3LESSON TWO: IP MULTICAST MODEL AND PROTOCOLS 11-18LESSON THREE: IP MULTICAST IN A SWITCHED LAN 11-38LESSON FOUR: IP MULTICAST DESIGN IN NBMA NETWORKS 11-58 Summary 11-68iv mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. APPENDICESAPPENDIX A: LABORATORY EXERCISES - APPLICATIONS AND IP MULTICASTA-1APPENDIX B: LABORATORY EXERCISES - INITIAL LAB SETUP B-13APPENDIX C: LABORATORY EXERCISES - IGMP CONCEPTS AND PIM DENSE MODE C-19APPENDIX D: LABORATORY EXERCISES - PIM SPARSE MODE CONCEPTSD-34APPENDIX E: LABORATORY EXERCISES - CGMP AND IGMP SNOOPINGE-47APPENDIX F: LABORATORY EXERCISES - SIMPLE IP MULTICAST DEPLOYMENTF-58APPENDIX G: LABORATORY EXERCISES - SOLUTIONS G-631Course Introduction Overview'Implementing Cisco Multicast (MCAST) version 1.0 is an instructor-led course presented by Cisco Systems, Inc. training partners to their end-user customers. This Iour-day course Iocuses on IP multicast technology, IP multicast protocols, and on the implementation oI IP multicast on Cisco routers and switches. Upon completion oI this training course, you will be able to design, implement, and troubleshoot IP multicast in simple network environments. OutIineThis course introduction describes the course prerequisites and course highlights, in addition to some administrative issues. It includes these sections: Course Obiectives Modules Obiectives earner Skills and Knowledge Learner Responsibilities General Administration Sources oI InIormation Course Roadmap Icons and Symbols Learner Introductions 1-2 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Course Objectives This section lists the course obiectives. 'Implementing Cisco Multicast provides learners with in-depth knowledge oI the IP multicast that make this new IP service deployable and attractive Irom a business perspective. Bandwidth and processing power are wasted when data is replicated and sent multiple times Irom a single source to multiple receivers. With IP multicast and a sophisticated group oI protocols, the inIormation is delivered with minimal impact on bandwidth and processor load, ensuring simultaneous delivery to only the people and machines that need it. The course covers the Iundamentals oI IP multicasting, which includes multicast applications, sources, receivers, group management, and IP multicast routing protocols (such as Protocol Independent Multicast, or PIM) used within a single administrative domain (intradomain). The issues oI switched LAN environments and reliable IP multicasting are covered as well. The course provides technical solutions Ior simple deployments oI IP multicast within a provider or customer network. The course provides conIiguration and troubleshooting guidelines Ior implementation oI IP multicast on Cisco IOS routers. The labs provide students with the direct personal involvement they need to successIully deploy IP multicast. 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-2Course Objectives Course ObjectivesUpon compIeting this course, you wiII be abIe to: Determine the need for IP muIticasting services ExpIain the IP muIticast modeI and its appIications Describe muIticast distribution trees and configure ProtocoI Independent MuIticast (PIM) protocoI List the soIutions for IP muIticast reIiabiIity Identify and soIve the probIems of IP muIticast in switched LAN environment and in WAN networks DepIoy IP muIticast in simpIe network scenariosCopyright 2003, Cisco Systems, nc. Course ntroduction 1-3 ModuIe Objectives This section lists the obiectives oI each module in the course. IP MuIticast TechnoIogy The 'IP Multicasting Concepts module provides an entry point to IP multicast services, presents the Iunctional model oI IP multicast, and gives an overview oI technologies present in IP multicasting. The module is a Iundamental part oI the entire IP multicast curriculum and contains the business, theoretical, and implementation background needed by designers, implementers, and operations staII in service provider and enterprise networks. The module explains multicast technologies on the data-link layer. 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-3IP MuIticasting Concepts IP MuIticasting ConceptsAt the end of this moduIe, you wiII be abIe to: Determine IP muIticasting services and impIementation needs List various types of muIticast appIications and determine their requirements Identify the IP muIticast conceptuaI modeI and its impIementation detaiIs ExpIain the issues of muIticast technoIogies on data-Iink Iayer1-4 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. PIM Dense Mode ProtocoIThe 'PIM Dense Mode Protocol module provides a detailed explanation oI the Protocol Independent Multicast dense mode (PIM DM) protocol as a representative oI dense mode multicast protocols. The PIM DM conIiguration and troubleshooting commands allow students to deploy multicast in a simple environment and get the Iundamental knowledge required Ior using more complex deployments based on sparse mode protocols. 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-4Objectives: PIM Dense Mode ProtocoIObjectives: PIM Dense Mode ProtocoIAt the end of this moduIe, you wiII be abIe to: ExpIain the principIes and detaiIed operation of PIM DM Identify the roIes of various PIM DM controI packets Identify the deficiencies of PIM DM Configure and troubIeshoot Cisco routers for PIM Dense modeCopyright 2003, Cisco Systems, nc. Course ntroduction 1-5 PIM Sparse Mode ProtocoI The 'PIM Sparse Mode Protocol module provides a detailed explanation oI what is currently the most scalable IP multicast routing protocolPIM sparse mode (PIM SM). The module covers the principles oI operation and protocol details and concludes with implementation and troubleshooting commands. Learners will become Iamiliar with the determinism built into sparse mode multicast protocols and will be prepared Ior complex redundant deployments oI IP multicast. Additionally the module presents the variants oI PIM SM, such as bidirectional PIM and Source SpeciIic Multicast. 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-5Objectives: Sparse Mode MuIticast ProtocoIsObjectives: Sparse Mode MuIticast ProtocoIsAt the end of this moduIe, you wiII be abIe to: ExpIain the principIes and detaiIed operation of PIM SM Identify the roIes of various PIM SM controI packets Configure and troubIeshoot PIM SM in nonredundant depIoyment Describe the variants of PIM SM (bidirectionaI PIM and Source Specific MuIticast)1-6 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. ReIiabIe IP MuIticasting The 'Reliable IP Multicasting module explains the problems that users Iace because oI the nature oI standard IP multicast based on User Datagram Protocol (UDP) transport. Some oI the approaches to reliability in IP multicasting are discussed. These approaches include applications such as Multicast FTP (MFTP) and Scalable Reliable Multicast (SRM) used in the whiteboard application, in addition to applications where the network assists in reliability, such as PGM. The module concludes with the implementation oI PGM in Cisco IOS soItware. 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-6Objectives: ReIiabIe IP MuIticastingObjectives: ReIiabIe IP MuIticastingAt the end of this moduIe, you wiII be abIe to: Describe the reIiabiIity and appIication requirement probIems of a basic IP muIticast modeI List existing technoIogies that introduce reIiabiIity into IP muIticast Configure and troubIeshoot Pragmatic GeneraI MuIticast (PGM)Copyright 2003, Cisco Systems, nc. Course ntroduction 1-7 ImpIementation of IP MuIticast on Data-Link Layer The 'Implementation oI IP Multicast on Data-Link Layer module presents the implementation details oI IP multicast and the issues oI data-link layer treatment oI multicast Irames. The module covers Cisco Group Management Protocol (CGMP) and Internet Group Management Protocol (IGMP) snooping as the two most common solutions in a switched LAN environment. Optimization oI multicast in nonbroadcast multiaccess (NBMA) networks with emphasis on ATM implementation is also discussed. 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-7Objectives: ImpIementation of IP MuIticast on Data-Link LayerObjectives: ImpIementation of IP MuIticast on Data-Link LayerAt the end of this moduIe, you wiII be abIe to: Configure Cisco routers and LAN switches for CGMP, IGMP snooping. and RGMP TroubIeshoot Cisco routers and LAN switches for IP muIticast in switched LAN networks Identify the probIems of IP muIticast on a data Iink Iayer of NBMA networks Configure and troubIeshoot PIM NBMA mode on Cisco routers1-8 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. ImpIementing Cisco MuIticast The Simple Intradomain Deployment oI IP Multicast module covers the basics oI IP multicast technology with respect to an implementation in relatively simple network environments. Throughout the module, various deployment scenarios are presented, and the beneIits and disadvantages are discussed. 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-8Objectives: SimpIe Intradomain DepIoyment of IP MuIticastObjectives: SimpIe Intradomain DepIoyment of IP MuIticastAt the end of this moduIe, you wiII be abIe to: Determine the business drivers for IP muIticast Assess the needs of a customer with respect to pIanned muIticast appIications ExpIain the depIoyment issues of the IP muIticast modeI SeIect muIticast protocoIs for different environments Design and impIement IP muIticast for simpIe networking environmentsCopyright 2003, Cisco Systems, nc. Course ntroduction 1-9 Learner SkiIIs and KnowIedge This section lists the course prerequisites.To Iully beneIit Irom 'Implementing Cisco Multicast, learners must possess certain knowledge and skills gained in a structured learning environment. These skills may be gained Irom selI-paced or instructor-led training sessions and Irom work experience. The best way to gain the skills needed to Iollow this course is to attend Cisco 'Interconnecting Cisco Network Devices (ICND) and 'Building Scalable Cisco Networks (BSCN) courses, either as selI-paced e-learning or instructor-led training. Learners gain more practical experience Irom the course iI they already have work experience and conIiguration skills Ior Cisco routers and LAN switches. These skills are best demonstrated through the Cisco CertiIied Networking ProIessional (CCNP) career certiIication. Previous exposure to internal routing protocols and LAN/WAN technologies allows learners to Iully beneIit Irom the discussions in the design sections oI the course. 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-9Basic IP MuIticast(MUBBM)Learner SkiIIs and KnowIedge Learner SkiIIs and KnowIedgeSuccessfuI compIetion of: Interconnecting Cisco Networks Devices (ICND) BuiIding ScaIabIe Cisco Networks (BSCN)Recommended:CCNP certification or equivaIent IeveI of IP routing and Cisco IOS knowIedge1-10 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Learner ResponsibiIities This section discusses learner responsibilities Ior the course. To take Iull advantage oI the inIormation presented in this course, you must have completed the prerequisite requirements. In class, you are expected to participate in all lesson exercises and assessments. In addition, you are encouraged to ask any questions relevant to the course materials. II you have pertinent inIormation or questions concerning Iuture Cisco product releases and product Ieatures, please discuss these topics during breaks or aIter class. The instructor will answer your questions or direct you to an appropriate inIormation source. 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-10Learner ResponsibiIities Learner ResponsibiIities CompIete prerequisites Introduce yourseIf Ask questionsCopyright 2003, Cisco Systems, nc. Course ntroduction 1-11 GeneraI Administration This section lists the administrative issues Ior the course. The instructor will discuss the administrative issues in detail, so you will know exactly what to expect Irom both the class and the Iacilities. The Iollowing items will be discussed: Recording your name on a sign-in sheet Start and anticipated end time oI each class day Materials you may expect to receive during the class Appropriate attire during class attendance Location oI rest rooms Emergency procedures Class breaks and lunch Iacilities Sending and receiving telephone, e-mail, and Iax messages 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-12GeneraI Administration GeneraI AdministrationCIass-reIated Sign-in sheet Length and times Participant materiaIs AttireFaciIities-reIated Rest rooms Site emergency procedures Break and Iunch room Iocations Communications1-12 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Sources of Information This section identiIies additional sources oI inIormation. To learn more about the subiects covered in this course, access the Iollowing sources oI inIormation. These supporting materials are available in HTML Iormat and as manuals and release notes. Cisco Documentation CD-ROM ITM CD-ROM Cisco IOS 12.1 ConIiguration GuideCisco IOS 12.1 Command ReIerence GuideMany oI these documents are Iound at the Cisco website: www.cisco.comCisco Press books and documents are Iound at this website: www.ciscopress.com 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-13Sources of Information Sources of Information Student kit www.cisco.com CD-ROMs Cisco PressCopyright 2003, Cisco Systems, nc. Course ntroduction 1-13 Course Roadmap This section covers the suggested order oI the course materials. The schedule here reIlects the recommended structure Ior this course. This structure allows suIIicient time Ior the instructor to present the course inIormation and Ior you to work through the laboratory exercises. The exact timing oI the subiect materials and labs depends on the pace oI the speciIic class. DetaiIed Overview The exact structure oI the course is six modules composed oI one or more lessons. Some oI the modules are accompanied by extensive lab exercises. The titles oI individual sections are listed in the roadmap here. A short description oI each module Iollows: IP Multicast Technology module (5.25 hours): The purpose oI this module is to introduce the technology background Ior IP multicast. The module includes these lessons: IP Multicasting Concepts IP Multicast Distribution Trees and Control Protocols IP Multicasting at Layer 2 PIM Dense Mode Protocol module (7 hours): The purpose oI this module is to describe the operation and conIiguration oI PIM Dense Mode protocol and to provide learners with necessary monitoring and troubleshooting skills Ior IP multicast. This is a single-lesson module. 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-14Course Roadmap Course RoadmapIP MuIticast - Benefits and CaveatsIP MuIticast AppIication TypesThe Basic ModeI of IP MuIticastIP MuIticast AddressingMuIticast Sessions - Directory ServicesFunctions ofMuIticast EnabIed NetworksMuIticast Distribution Trees and ProtocoI TypesOverview of IP MuIticast Routing ProtocoIsReporting Group MembershipMuIticast MAC-Layer Addresses and Switch ForwardingConstraining MuIticast Streams on LAN Switch PortsPIM Sparse Mode OverviewPIM Sparse Mode DetaiIsPIM Sparse Mode ImpIementation and TroubIeshootingBidirectionaI PIM and Source Specific MuIticast1. IP MuIticast TechnoIogyPIM Dense Mode OverviewPIM Dense Mode DetaiIsPIM Dense Mode ImpIementation and TroubIeshooting2. PIM Dense Mode ProtocoI3. Sparse Mode MuIticast ProtocoIs1-14 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Sparse Mode Multicast Protocols module (5 hours): The purpose oI this module is to describe the operation and conIiguration oI PIM Sparse Mode protocol. The variants oI PIM Sparse Mode including Bi-directional PIM and Source SpeciIic Multicast are discussed as well. The module includes these lessons: PIM Sparse Mode PIM SM Implementation and Variants oI PIM SM Copyright 2003, Cisco Systems, nc. Course ntroduction 1-15 The remaining modules oI this course and titles oI individual sections are listed in the roadmap here. A short description oI modules Iollows: Reliable IP Multicasting module (1 hour): The purpose oI this module is to explain the issues oI reliable IP multicasting and to present some solutions. This module is a single-lesson module. Implementation of IP Multicast on Data-Link Layer module (3 hours): The purpose oI this module is to explain the issues oI data-link layer reality in IP multicast implementation and to present some solutions. The module includes these lessons: IP Multicasting in Switched LAN Environment IP Multicast Implementation in NBMA Networks Simple Intradomain Deployment of IP Multicast module (3.5 hours): The purpose oI this module is to describe the design and implementation issues oI IP multicast in a simple network environment. This is a single-lesson module. 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-15Course Roadmap (cont.) Course Roadmap (cont.)What is ReIiabIe IP MuIticast?Cisco IOS ImpIementtion of PGMMuIticast AppIications RequirementsIP MuIticast ModeI and ProtocoIsIP MuIticast in a Switched LANIP MuIticast Design in NBMA Networks4. ReIiabIe IP MuIticastingCGMP ImpIementationIGMP Snooping ImpIementationRGMP ImpIementationProbIems of Running IP MuIticast over NBMA MediaPIM NBMA Mode5. ImpIementation of IP MuIticast on Data Link Layer6. SimpIe Intradomain IP MuIticast DepIoyment1-16 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Learner Introductions This is the part oI the course where you introduce yourselI. Prepare to share the Iollowing inIormation: Your name Your company II you have most or all oI the prerequisite skills A proIile oI your experience, including a brieI description oI your experience with installing and conIiguring Cisco routers, attending other Cisco classes, and how your work experience helped you meet the prerequisites highlighted earlier 2000, CiscoSystems, Inc. www.cisco.com MUBBM v1.0-16Learner Introductions Learner Introductions Your name Your company Prerequisite skiIIs Brief history Objective2IP Multicast Technology OverviewThis module provides an entry point to IP multicast services, presents the Iunctional model oI IP multicasting, and gives an overview oI technologies present in IP multicasting. The learner will learn about IP multicasting, its beneIits and associated caveats, and will determine various types oI multicast applications. The learner will gain an understanding oI the IP multicast conceptual model and its implementation prerequisites. OutIineThe module includes these topics: ObiectivesIP Multicast BeneIits and Caveats IP Multicast Application Types The Basic Model oI IP Multicast IP Multicast Addressing Multicast Sessions Directory Services Summary 2-2 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. ObjectivesUpon completion oI this module, you will be able to: Explain the beneIits oI multicasting and identiIy possible caveats. List various types oI multicast applications and their requirements. Present the basic conceptual IP multicast model. IdentiIy the addressing issues oI IP multicasting. Explain the way multicast applications work, and identiIy the prerequisites that have to be IulIilled Ior an implementation. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 2Objectives ObjectivesUpon compIetion of this chapter, the student wiII be abIe to: ExpIain the benefits of muIticasting and identify possibIe caveats List various types of muIticast appIications and expIain their requirements Describe the basic conceptuaI IP muIticast modeI Identify the addressing issues of IP muIticasting Determine the way muIticast appIications work and the prerequisites that have to be fuIfiIIed for an impIementationCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-3 IP MuIticast - Benefits and Caveats ObjectivesUpon completion oI this lesson, you will be able to: Compare traditional unicast delivery to multicast data distribution. Explain the beneIits oI IP multicasting. Indicate possible problems associated with IP multicasting. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 4Objectives ObjectivesUpon compIetion of this section, the student wiII be abIe to: Compare traditionaI unicast deIivery to muIticast data distribution List the benefits of IP muIticasting Indicate possibIe probIems associated with IP muIticasting2-4 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Multicast may be used to send the same data packets to multiple receivers. By sending to multiple receivers, the packets are not duplicated Ior every receiver, but are sent in a single stream, where downstream routers perIorm packet multiplication over receiving links.Routers process Iewer packets because they receive only a single copy oI the packet. This packet is then multiplied and sent on outgoing interIaces where there are receivers. Because downstream routers perIorm packet multiplication and delivery to receivers, the sender or source oI multicast traIIic does not have to know the unicast addresses oI the receiver. Simulcast, simultaneous delivery Ior a group oI receivers, may be used Ior several purposes including audio/video streaming, news and similar data delivery, and deploying soItware upgrades. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 5Why MuIticast? Why MuIticast? Used when sending same data to muItipIe receivers Better bandwidth utiIization Less host/router processing Used when receivers' addresses unknown Used when simuItaneous deIivery for a group of receivers is required ("simuIcast")Copyright 2003, Cisco Systems, nc. P Multicast Technology 2-5 To send data to multiple destinations using unicast, the sender has to send Ior each receiver its own data Ilow. The sender has to make copies oI the same packet and send them once Ior each receiver.Some web technologies (Ior example, webcasting) use a 'push method to deliver the same data to multiple users. Instead oI users clicking on a link to get the data, the data is delivered automatically. Users Iirst have to subscribe to a channel to receive the data, and, aIter that, the data is periodically 'pushed to the user. The problem with the webcast is that the transport is still done using unicast. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 6Sending to MuItipIe Destinations Sending to MuItipIe Destinations Pure Unicast: Send the same copy of data muItipIe times Web TechnoIogies: Webcasting-"push" the same data to muItipIe destinations TraditionaIIy, receivers subscribed to data and "puIIed" it down periodicaIIy The underIying transport for those TechnoIogies has been Unicast2-6 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Unicast transmission sends multiple copies oI data, one copy Ior each receiver: The example above shows a host transmitting three copies oI data and a network Iorwarding each packet to three separate receivers. The host may only send to one receiver at a time, because it has to create a diIIerent packet destination address Ior each receiver. Multicast transmission sends a single copy oI data to multiple receivers. The example below shows a host transmitting one copy oI data and a network replicating the packet at the last possible hop Ior each receiver. Each packet exists only in a single copy on any given network. The host may send to multiple receivers simultaneously because it is sending only one packet. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 7Unicast versus MuIticast Unicast versus MuIticastHostRouterUnicastHostRouterMuIticastCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-7 In multicast, the sender sends only one copy oI a single data packet addressed to a group oI receivers multicast group. Downstream multicast routers replicate and Iorward the data packet to all those branches where receivers (may) exist. Receivers express their interest in multicast traIIic by registering at their Iirst-hop router using the Internet Group Management Protocol (IGMP) protocol. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 8IP MuIticast - How Does it Work? IP MuIticast - How Does it Work? The sender (source) sends one copy of a singIe packet addressed to a group of receivers - muIticast group MuIticast routers repIicate and forward the packet to aII the branches where receivers (may) exist Receivers express their interest in muIticast traffic by sending controI messages to routers2-8 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Multicast transmission provides many advantages over unicast transmission in a one-to-many or many-to-many environment: Enhanced Efficiency: Available network bandwidth is utilized more eIIiciently because multiple streams oI data are replaced with a single transmission. Optimized Performance: Fewer copies oI data require Iorwarding and processing. Distributed Applications: Multipoint applications will not be possible as demand and usage grows, because unicast transmission will not scale (traIIic level and clients increase at a 1:1 rate with unicast transmission). 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 9ExampIe: Audio StreamingAII cIients Iistening to the same 8-Kbps audio Enhanced Efficiency: ControIs network traffic and reduces server and CPU Ioads Optimized Performance: EIiminates traffic redundancy Distributed AppIications: Makes muItipoint appIications possibIe00.20.40.60.8TrafficMbps1 20 40 60 80 100Number of CIientsMuIticastUnicastMuIticast Advantages MuIticast AdvantagesCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-9 There are other multicast advantages: For the equivalent amount oI multicast traIIic, the sender needs much less processing power and bandwidth. Multicast packets do not impose high bandwidth utilization as unicast packets, so there is a greater possibility they will arrive almost simultaneously at the receivers. Multicast enables a whole range oI new applications that were not possible on unicast (Ior example, Video On Demand). 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 10MuIticast Advantages (cont.) MuIticast Advantages (cont.) Fewer resources required - bandwidth and host processing power (at sender) AImost simuItaneous deIivery is assured (one packet is simuItaneousIy forwarded across the networks) Foundation for a whoIe range of new appIications not possibIe in the past2-10 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. There are also some disadvantages oI multicast that need to be considered. Most multicast applications are User Datagram Protocol (UDP) based. This Ioundation results in some undesirable consequences when compared to similar unicast, TCP applications.Best eIIort delivery results in occasional packet drops. Many multicast applications that operate in real time (Ior example, video, audio) may be aIIected by these losses. Also, requesting retransmission oI the lost data at the application layer in these not quite real-time applications is not Ieasible. Heavy drops on voice applications result in ierky, missed speech patterns that can make the content unintelligible when the drop rate gets high enough. Moderate to heavy drops in video is sometimes better tolerated by the human eye and appear as unusual 'artiIacts in the picture. However, some compression algorithms may be severely aIIected by even low drop rates: this causes the picture to become ierky or to Ireeze Ior several seconds while the decompression algorithm recovers. No congestion control may result in overall network degradation as the popularity oI UDP based multicast applications grow. Duplicate packets may occasionally be generated as multicast network topologies change. Applications must expect occasional duplicate packets to arrive and must be designed accordingly. Out oI sequence delivery oI packets to the application may also result during network topology changes or other network events that aIIect the Ilow oI multicast traIIic. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 11MuIticast Disadvantages MuIticast Disadvantages MuIticast is UDP based. Best Effort DeIivery: Drops are to be expected. MuIticast appIications must not expect reIiabIe deIivery of data and shouId be designed accordingIy. ReIiabIe muIticast wiII address this issue. No Congestion Avoidance: Lack of TCP windowing and "sIow-start" mechanisms can resuIt in network congestion. If possibIe, muIticast appIications shouId attempt to detect and avoid congestion conditions. DupIicates: Some muIticast protocoI mechanisms resuIt in the occasionaI generation of dupIicate packets. MuIticast appIications shouId be designed to expect occasionaI dupIicate packets. Out of sequence deIivery: Network topoIogy changes affect the order of deIivery - the appIication must properIy address the issue.Copyright 2003, Cisco Systems, nc. P Multicast Technology 2-11 Additionally, there are other multicast disadvantages. UDP has no reliability mechanisms, so reliability issues have to be addressed in multicast applications where reliable data transIer is necessary. Restricting multicast traIIic to only a selected group oI receivers. Eavesdropping issues are not suIIiciently solved yet. Only when reliability and security issues are properly solved will some commercial applications be possible (Ior example, Iinancial data delivery). 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 12MuIticast Disadvantages (cont.) MuIticast Disadvantages (cont.) ReIiabiIity is a speciaI issue not addressed in originaI IP muIticast research Security is another area in IP muIticast not sufficientIy soIved in the past Proper soIutions to the above issues wiII open opportunities for severaI commerciaI appIications (e.g. financiaI data deIivery)2-12 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. SummaryUpon completion oI this lesson, you must be able to: Compare traditional unicast delivery to multicast data distribution. Explain the beneIits oI IP multicasting. Indicate possible problems associated with IP multicasting. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 13Summary SummaryAfter compIeting this section, the student shouId be abIe to: Compare traditionaI unicast deIivery to muIticast data distribution List the benefits of IP muIticasting Indicate possibIe probIems associated with IP muIticastingCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-13 Review Questions How many copies oI the same data are sent by an IP multicast-enabled sender? How many copies oI the same packet are Iorwarded by IP multicast routers? List the beneIits and explain the disadvantages oI IP multicast. Which IP multicast issues were not addressed suIIiciently in the past? 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 14Review Questions Review Questions How many copies of the same data are sent by an IP muIticast-enabIed sender? How many copies of the same packet are forwarded by IP muIticast routers? List the benefits and disadvantages of IP muIticast. Which IP muIticast issues were not addressed sufficientIy in the past?2-14 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. IP MuIticast AppIication Types ObjectivesUpon completion oI this lesson, you will be able to: IdentiIy the types oI applications suitable Ior implementation in an IP multicast environment. Assess the requirements oI those applications. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 16Objectives ObjectivesUpon compIetion of this section, the student wiII be abIe to: Identify the types of appIications suitabIe for impIementation in IP muIticast environments Assess the requirements of those appIicationsCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-15 There are diIIerent types oI multicast applications. Here are two oI the most common models: One-to-many model, where one sender sends data to many receivers Many-to-many model, where a host can be a sender in addition to a receiver simultaneously Other models (Ior example, many-to-one, where many receivers are sending data back to one sender or Iew-to-many) are also used, especially in Iinancial applications/networks. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 17Types of MuIticast AppIications Types of MuIticast AppIications One-to-many: A singIe host sending to two or more (n) receivers Many-to-many: Any number of hosts sending to the same muIticast group-hosts are aIso members of the group (sender = receiver) Other, e.g. many-to-one: Any number of receivers sending data back to a source (via unicast or muIticast)2-16 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Many new multipoint applications are emerging as demand Ior them grows. Real-time applications include live broadcasts, Iinancial data delivery, whiteboard collaboration, and video conIerencing. Non-real-time applications include Iile transIer, data and Iile replication, and video on demand (VoD). 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 18Corporate Broadcasts Corporate BroadcastsDistance LearningDistanceLearningTraining TrainingVideoConferencingVideoConferencingWhiteboard/CoIIaborationWhiteboard/CoIIaborationMuIticastFiIeTransferMuIticastFiIeTransferDataandFiIeRepIicationDataandFiIeRepIicationReaI ReaI- -Time Data DeIivery Time Data DeIivery- -FinanciaI FinanciaIVideoVideo- -OnOn- -DemandDemandLive TV and Radio Broadcast Live TV and Radio Broadcast to the Desktop to the DesktopIP MuIticast AppIications IP MuIticast AppIicationsCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-17 The one-to-many multicast application, where a single source is sending to an unknown group oI receivers, is the simplest type oI application. This application may be used Ior audio/video distribution, push-media, announcements, monitoring, and so on. II a one-to-many application needs a Ieedback Irom receivers, it becomes a many-to-many application. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 19One-to-Many MuIticast One-to-Many MuIticast The simpIest type of an appIication A singIe source is sending to a muIticast group ("broadcasting") Receiver popuIation typicaIIy not known -no feedback Audio/video distribution, push-media, announcements, monitoring (stock quotes) Some one-to-many appIications become many-to-many (periodic feedback information)2-18 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Many-to-many multicast applications are those where two or more receivers also act as senders. Receiving data Irom several sources increases the complexity oI applications and creates diIIerent management challenges. Using a many-to-many multicast concept as a Ioundation, a whole new range oI applications may be built (Ior example, collaboration, concurrent processing, and distributed interactive simulations) 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 20Many-to-Many MuIticast Many-to-Many MuIticast EnabIes the most unique and powerfuI appIications Any host can send to a muIticast group in addition to receive from it - receivers known SimuItaneous reception from severaI sources - compIex coordination MuItimedia conferencing, coIIaboration, synchronization of resources, and so on Foundation for a set of new appIicationsCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-19 The many-to-one multicast model may be used Ior resource discovery, data collection, and similar applications, but building them imposes several challenges. Maintaining a multicast state in networks with many senders may cause scaling problems in the network that are transparent to the application. Many senders may cause message implosion problems at the receiver side. There are some solutions to these problems (Ior example, bidirectional trees in multicast routing), but application developers must be aware oI these problems. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 21Other MuIticast Types Other MuIticast Types Many-to-one is a speciaI type that has severaI chaIIenges TypicaIIy two way request/response-either end (many or one) generates request ImpIosion probIem/response storm-responses arrive simuItaneousIy Resource discovery, data coIIection, auctions, poIIing, and so on Can be combined with other types; responses can be sent "out-of-band" 2-20 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Basically, one-to-many applications (Ior example, Iile distribution) are tolerant to delays, but there are also some applications that are sensitive to iitter (Ior example, audio/video conIerencing) and some that are not tolerant to delays at all (Ior example, real-time monitoring, Iinancial applications). Many-to-many applications are intolerant to delays because they are bidirectional. Delays in multimedia conIerencing higher than 500 ms may be very disturbing to the audience. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 22MuIticast AppIications RequirementsMuIticast AppIications Requirements One-to-many appIications typicaIIy more toIerant to deIays Audio / video more sensitive to jitter ReaI-time monitoring Iess toIerant Many-to-many appIications intoIerant to deIays since they are bi-directionaI Conference appIications very strict - deIays higher than 500 ms disturbingCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-21 DiIIerent multicast applications have diIIerent bandwidth needs. II there is not enough bandwidth, applications may adiust the encoding techniques to use less bandwidth. That is why applications need the Ieedback inIormation about how much oI bandwidth is available. Audio/video applications use Real-Time Transport Protocol (RTP)/Real Time Control Protocol (RTCP) to get the Ieedback about available bandwidth Irom the network. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 23MuIticast AppIications Requirements (cont.)MuIticast AppIications Requirements (cont.) Bandwidth requirements depend on the size of a muIticast stream When the bandwidth is scarce, the source may adjust the encoding techniques Feedback information is needed - audio / video distribution uses RTP / RTCP (ReaI-Time Transport ProtocoI / ReaI-Time ControI ProtocoI)2-22 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Just as its name implies, this is a Iorm oI electronic whiteboard application that may be shared by members oI the multicast group. Whiteboard uses a Iorm oI reliable multicast. Reliable multicast transport is necessary to ensure that no loss oI critical graphic inIormation occurs. Whiteboard uses the Scalable Reliable Multicast (SRM) protocol to ensure reliable delivery. Most multimedia multicast applications simply use UDP, 'best eIIort datagram delivery mechanisms because oI the time critical nature oI the media. However, whiteboard application needs a reliable method to distribute the graphic images drawn on the electronic whiteboard. Audio and video distribution applications use diIIerent encoding techniques to minimize the bandwidth use. To get the inIormation about the available bandwidth and to reserve it Ior their use, they use RTP/RTCP protocols. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 24MuIticast AppIicationsConceptuaI SchemeMuIticast AppIicationsConceptuaI SchemeMuIticast AppIications MuIticast AppIicationsAudio Video OtherWhiteboardG.7xx, PCM H.261, MPEG ..........RTP/RTCPOther transportsReIiabIe Transport (SRM)UDP UDPIP IPCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-23 First multicast applications emerged in Mbone (multicast backbone oI the Internet) including these applications: SDR (Session Directory): Session Directory is a tool that allows multicast group members to view advertised multicast sessions and launch appropriate multicast applications to ioin an existing session. Originally, it was based on SD (Session Directory), but SD and SDR are not compatible, because SDR implements a later version oI the Session Description Protocol (SDP). VAT (Visual Audio Tool): Audio conIerencing allows multiple learners to share audio interactively. VAT is based on the RTP. VIC (Video Conferencing): Video conIerencing allows multiple learners to share video and audio interactively. VIC was designed with a Ilexible and extensible architecture to support heterogeneous environments and conIigurations. WB (Whiteboarding): Whiteboarding allows multiple learners to collaborate interactively in a text and graphical environment. Documents may be either in PostScript or plain ASCII text.There are also some other Mbone multicast applications: Ior example RAT (Robust Audio Tool) and CU-SeeMe. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 25MuIticast AppIications ExampIe MuIticast AppIications ExampIe MBone MuIticast TooIs - first set of muIticast appIications: Sdr-session directory Lists advertised sessions and Iaunches muIticast appIication(s) Vat (visuaI audio tooI) and Rat (robust audio tooI) - audio conferencing Various types of audio compression (PCM, DVI, GSM, LPC4) Vic (Video Conferencing) - video conferencing H.261 video compression Wb (Whiteboarding) - whiteboarding Shared drawing tooI Uses ReIiabIe MuIticast (SRM - ScaIabIe ReIiabIe MuIticast)2-24 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. The slide shows the VAT audio conIerencing tool. On the leIt is the main window Ior the session. That window contains a speaker gain slider widget and an output Volume Unit (VU) bar-graph meter in addition to a microphone gain slider widget and VU meter. When someone wants to address the conIerence, they usually click the right mouse button on the workstation. The window on the right is a menu that may be activated by clicking the Menu button on the main window. This menu allows various parameters about the session to be adiusted including encoding Iormat. Notice that there are several members oI this session listed in the main window even though only the second person is talking (indicated by the blackened square next to the name). This activity indicates that all members oI the session are multicast sources, even though they may never speak and may only listen to the session. The reason is because VAT uses the RTP/RTCP model to transport real-time audio data. In this model, all members oI the session multicast member inIormation and reception statistics to the entire group in an RTCP back channel.Almost all multimedia multicast applications use the RTP/RTCP model including these applications:VAT (and its cousin application RAT) VICWB - (Whiteboard) Cisco IP/TV (Internet Protocol /TeleVision) 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 26VAT- Audio Conferencing VAT- Audio ConferencingCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-25 The slide shows an example oI the VIC video conIerencing tool. The window on the right is the main window Ior the video conIerencing session. Notice that multiple video streams are being received, each with their own 'thumbnail image. The window on the leIt is a larger version oI the thumbnail image Irom the main window. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 27VIC - Video Conferencing VIC - Video Conferencing2-26 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. The slide shows an example oI the whiteboard (WB) tool. The window on the leIt is the main window Ior the whiteboarding session. AIter checking the Receive Only check box in the right window you may draw or type in the main window. You may also import PostScript or ASCII text Iiles and put their contents on the whiteboard. The window on the right is a control window where learners are displayed in addition to the last one who changed the contents oI the whiteboard. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 28WB - Whiteboard WB - WhiteboardCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-27 ITU-T H.32x recommendations speciIy technical requirements Ior narrowband visual telephone systems and terminal equipment, typically Ior videoconIerencing and videophone services. The transport media is deIined by x (x 1 ISDN, x 3 LAN, x 4 analog). Recommendation G.7xx speciIies audio codecs and consist oI standards. These standards include G.711, which uses PCM encoding at a bit-rate Irom 48 to 64 kbps, and G.723.1, which uses algebraic code excited linear prediction (ACELP) encoding at 5.3 kbps and several others. Recommendation H.261 speciIies a video codec Ior audiovisual services at p x 64 kbps and H.263 speciIies video coding Ior low bit rate communication. Recommendations T.12x speciIy a multipoint communication service, which includes whiteboarding applications and multipoint Iile transIers. H.32x is an application standard that does not deIine the underlying transport protocol, hence IP multicast can be used. The H.32x standard is also supported by Cisco IOS soItware and components oI this standard are integrated into Cisco routers as multimedia conIerence manager soItware. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 29H.32x Videoconferencing FrameworkH.32x Videoconferencing Framework ITU-T standard for videoconferencing H.32x - x=1 ISDN, x=3 LAN, x=4 AnaIog Audio (G.7xx) and video (H.26x) encoding, controI protocoIs Support for whiteboarding (T.12x) May empIoy IP muIticast as a transport EIements impIemented in Cisco routers as MuItimedia Conference Manager2-28 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Senders may use the Ieedback inIormation Irom receivers to perIorm these types oI activities: Learn about the quality oI reception, and adiust the rate oI sending or encoding. Provide recovery in a case oI packet loss. IdentiIy the population oI receivers. Multicast Ilows Irom the sender and Irom receivers may be encrypted Ior security reasons. II the receivers are not known to the sender, encryption may be done only one way. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 30QuaIity / Security in MuIticast QuaIity / Security in MuIticast Feedback information is needed by senders to: Determine the quaIity of reception and adjust the rate of sending or encoding Provide recovery in case of packet Ioss (reIiabIe muIticast) Learn / identify the popuIation of receivers Security: when receivers are not known, encryption is the onIy way to secure dataCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-29 Real-Time Transport Protocol (RTP) provides network independent, end-to-end transport services Ior real-time applications. ThereIore it may be used as a transport protocol Ior audio or video data transIer. Some services that RTP provides include the Iollowing: Data sequencing Time stamping Payload type identiIication Delivery monitoring It is also important to know these services that RTP does not provide: Reliability Quality oI service Preventing out-oI-order delivery RTP uses special relays called Ior synchronization. Mixers may be used to combine separate video streams into one video stream or encode an original stream appropriate Ior high-bandwidth network into a stream suitable Ior a low-bandwidth link. RTP enioys strong industry support. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 31ReaI-Time Transport ProtocoI -RTPReaI-Time Transport ProtocoI -RTP ReaI-Time ProtocoI (RFC-1889 / 1890) is used as a transport protocoI for audio / video Provides sequence and timestampingwithout overhead required for reIiabIe sessions - does not ensure reIiabiIity EnabIes synchronization of separate streams Strong industry support2-30 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. When a host wants to request a speciIic quality oI service Irom the network, the Real-Time Control Protocol (RTCP) may be used. All learners in the multicast session (senders and receivers) periodically send RTCP control packets. Control packets are used to provide the Ieedback loop to the sender in addition to the receivers because it is sent as a multicast. As each learner hears control packets Irom all other learners, it may use that inIormation to limit the rate it sends them to the network. RTCP packets may use only up to 5 oI available bandwidth. By limiting the number oI control packets, the scalability oI RTCP is ensured. Because every receiver is also a sender, the traIIic is asymmetrical. It Ilows toward the receivers in addition to the sender. When the sender receives a control packet, it may adapt to changes in the network (available bandwidth, congestion, and so on) and keep track oI the receivers. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 32ReaI-Time ControI ProtocoI -RTCPReaI-Time ControI ProtocoI -RTCP The feedback Ioop in RTP provided via RTCP (ReaI-Time ControI ProtocoI) Sent to the same muIticast group RTCP packets can use up to 5% of avaiIabIe bandwidth Every receiver is a sender as weII -traffic is asymmetricaI EnabIes the source to adapt to quaIity of the network and to Iog the activity of membersCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-31 SummaryUpon completion oI this lesson, you must be able to: IdentiIy the types oI applications suitable Ior implementation in an IP multicast environment. Assess the requirements oI those applications. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 33Summary SummaryAfter compIeting this section the student shouId be abIe to: Identify the types of appIications suitabIe for impIementation in IP muIticast environment Assess the requirements of those appIications2-32 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Review Questions Which type oI multicast application is the most common and emulates a traditional broadcast? Why is delay an important issue Ior many-to-many multicast applications? How do participants oI an audio conIerence (using MBONE tools) identiIy each other? List some applications where Ieedback inIormation is a requirement. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 34Review Questions Review Questions Which type of a muIticast appIication is the most common and emuIates traditionaI broadcast? Why is deIay is an important issue for many-to-many muIticast appIications? How do participants of an audio conference (using Mbone tooIs) identify each other? List some appIications where feedback information is a requirement.Copyright 2003, Cisco Systems, nc. P Multicast Technology 2-33 The Basic ModeI of IP MuIticast ObjectivesUpon completion oI this lesson, you will be able to: Describe the need Ior splitting multicast delivery path into various segments. IdentiIy Iunctions needed on source, network, and receiver segments. Explain the protocols used within the IP multicasting model. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 36Objectives ObjectivesUpon compIetion of this section, the student wiII be abIe to: Describe the need for spIitting the muIticast deIivery path into various segments Identify functions needed on source, network, and receiver segments ExpIain the protocoIs used within the IP muIticasting modeI2-34 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. RFC 1112 speciIies the host extensions to IP protocol to support multicast. Allows hosts to ioin a group that receives multicast packets Allows users to dynamically register (ioin/leave multicast groups) based on the applications they use Uses IP datagrams to transmit data Each multicast group is deIined by a Class D IP address (224.0.0.0 to 239.255.255.255). Addresses are allocated dynamically and represent receiver groups, not the individual hosts. Receivers may dynamically ioin/leave a multicast group at any time using IGMP messages. Messages are sent to the routers, which manage group membership. Senders are not necessarily included in the multicast group they are sending to. Many applications have the characteristics oI receivers also becoming senders: Ior example, RTCP streams Irom IP/TV clients and Tibco Rendezvous product. Routers use multicast routing protocols (Ior example, DVMRP, MOSPF, CBT, and so on) to eIIiciently Iorward multicast data to multiple receivers. The routers listen to all multicast addresses and create multicast distribution trees, which are used Ior multicast packet Iorwarding. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 37IP MuIticast Service ModeI IP MuIticast Service ModeI RFC 1112 "Host Extensions for MuIticast Support" Each muIticast group is identified by a cIass D IP address Members join and Ieave the group and indicate this to the routers Routers Iisten to aII muIticast addresses and use muIticast routing protocoIs to manage groupsCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-35 Routers identiIy multicast traIIic and Iorward the packets Irom senders toward the receivers. When the source becomes active, it iust starts sending the data without any indication. First-hop routers, to which the sources are directly connected, start Iorwarding the data to the network.Receivers that are interested in receiving multicast data register to last hop routers using IGMP membership messages. Last-hop routers are those routers that have directly connected receivers. These routers Iorward the group membership inIormation oI their receivers to the network: this way the other routers are inIormed about which multicast Ilows are needed. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 38IP MuIticast Service ModeI (cont.) IP MuIticast Service ModeI (cont.) MuIticast network routers are distinct from source and receiver segments Sources simpIy start sending data without any indication First-hop routers forward data Receivers report their membership to Iast hop routers Last-hop (Ieaf) routers communicate group membership to the network 2-36 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. The example above shows a source connected to a Iirst-hop router, which Iorwards multicast packets into the network. Packets traverse the source path trees (SPT) on their way to the receivers toward the last-hop router. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 39MuIticast ConceptuaI ModeI MuIticast ConceptuaI ModeISourceSource segmentFirst-hop routerLast-hop routerMuIticast distribution treeReceiver segmentMuIticast data fIowCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-37 The multicast network routers learn about their multicast-enabled neighbors to build appropriate distribution trees. As they build the distribution tree, they start Iorwarding multicast traIIic according to network needs. During the normal operation, routers maintain the distribution tree and multicast group state at leaI segments. The routers also prevent loops and apply scoping or Iiltering. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 40Functions of a MuIticast Network Functions of a MuIticast Network Learn about muIticast group members and buiId an appropriate distribution tree Identify muIticast streams and forward them according to a distribution tree Maintain: Group state at Ieaf segments Distribution tree in the whoIe network Prevent Ioops and appIy scoping / fiItering2-38 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Multicast sources create a session and announce it via session announcements. These sources originate multicast data and send it to a multicast group. II there is any Ieedback received Irom the receivers, they apply proper actions: Ior example, change data encoding to compensate Ior lower bandwidth. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 41MuIticast Sources MuIticast Sources Create a session / group and announce it via session announcement Originate muIticast data and send it to a muIticast group AppIy proper actions if feedback information is avaiIabIeCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-39 Multicast receivers listen to the session announcements or use some other mechanism to learn about the available sessions. Receivers may select certain multicast groups and report their interest by sending a Register message to the router. The router then starts Iorwarding speciIied multicast group traIIic to the receivers.AIter receivers start receiving multicast data, they maintain their group membership and may also provide the Ieedback to the source on the received data. When receivers want to stop receiving certain multicast data, they send a Leave message to the router. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 42MuIticast Receivers MuIticast Receivers Listen for session announcements or use some other mechanism to Iearn about avaiIabIe sessions Report their interest in a certain group by sending messages to the routers Receive muIticast data and provide feedback if needed Maintain their group membership and Ieave the group when necessary2-40 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. There is no multicast protocol Ior source registering used between the source and the Iirst-hop router, such as IGMP, which is used between the last-hop router and receiver. Inside the multicast network, there are various multicast routing protocols used. The multicast routing protocols may be separated into these two groups: Intradomain (Ior example, Distance Vector Multicast Routing Protocol |DVMRP|, PIM, Multicast Open Shortest-Path First |MOSPF|, Core Based trees |CBTs|) Interdomain (Ior example, Multiprotocol BGP Extensions Ior IP Multicast |MBGP| in combination with Multicast Source Discovery Protocol |MSDP|) Between the last-hop router and the receivers, IGMP is used. Receivers use IGMP to report their multicast group membership to the router. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 43MuIticast ProtocoIs MuIticast ProtocoIs No controI protocoIs spoken at source segments MuIticast routing protocoIs used in a muIticast network: Intradomain (DVMRP, PIM and variants, MOSPF, CBT) Interdomain (MBGP/MSDP) Receiver segments use IGMP (Internet Group Management ProtocoI)Copyright 2003, Cisco Systems, nc. P Multicast Technology 2-41 The slide shows multicast protocols used in a multicast network. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 44MuIticast ProtocoIs (cont.) MuIticast ProtocoIs (cont.)SourceNo signaIingMuIticast routing protocoIsIntradomain: DVMRP, PIM, MOSPF, CBTInterdomain: MBGP/MSDPIGMPSource2-42 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. SummaryUpon completion oI this lesson, you must be able to: Describe the need Ior splitting multicast delivery path into various segments. IdentiIy Iunctions needed on source, network, and receiver segments. Explain the protocols used within the IP multicasting model. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 45Summary SummaryAfter compIeting this section, the student shouId be abIe to: Describe the need for spIitting the muIticast deIivery path into various segments Identify functions needed on source, network, and receiver segments ExpIain the protocoIs used within the IP muIticasting modeICopyright 2003, Cisco Systems, nc. P Multicast Technology 2-43 Review Questions How do Iirst hop routers learn about multicast data sent by a source? How do receivers know what sessions are available? What happens when receivers start a multicast application? List some multicast routing protocols used within a domain. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 46Review Questions Review Questions How do first hop routers Iearn about muIticast data sent by a source? How do receivers know what sessions are avaiIabIe? What happens when receivers start a muIticast appIication? List some muIticast routing protocoIs used within a domain.2-44 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. IP MuIticast Addressing ObjectivesUpon completion oI this lesson, you will be able to: Explain how the multicast address range is split into various Iunctional groupings. List IP multicast address assignment methods that exist or are in development. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 48Objectives ObjectivesUpon compIetion of this section, the student wiII be abIe to: ExpIain how the muIticast address range is spIit into various functionaI groupings List IP muIticast address assignment methods that exist or are in deveIopmentCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-45 Multicast IP addresses use the Class D address space. Class D addresses are denoted by the high-order 4 bits set to 1110. The multicast IP address space is separated into the Iollowing address groups: Local scope addresses are addresses 224.0.0.0 through 224.0.0.255 and are reserved by Internet Assigned Numbers Authority (IANA) Ior network protocol use. Multicasts in this range are never Iorwarded oII the local network regardless oI Time To Live (TTL), and usually the TTL is set to 1. Here are examples oI local multicast addresses: 224.0.0.1 All Hosts 224.0.0.2 All Multicast Routers 224.0.0.3 All DVMRP Routers 224.0.0.5 All OSPF Routers 224.0.0.6 All OSPF DR Global scope addresses are addresses 224.0.1.0 through 238.255.255.255 and are allocated dynamically throughout the Internet. Administratively scoped addresses are addresses 239.0.0.0 through 239.255.255.255 and are reserved Ior use inside private domains. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 49IP MuIticast Basic AddressingIP MuIticast Basic Addressing IP group addresses CIass D address - high-order 3 bits are set Range from 224.0.0.0 through 239.255.255.255 WeII-known addresses assigned by IANA Reserved use: 224.0.0.0 through 224.0.0.255 224.0.0.1 - aII muIticast systems on subnet 224.0.0.2 - aII routers on subnet 224.0.0.4 - aII DVMRP routers 224.0.0.13 - aII PIMv2 routers 224.0.0.5, 224.0.0.6, 224.0.0.9, 224.0.0.10 used by unicast routing protocoIs2-46 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Global scope multicast addresses and administratively scoped multicast addresses are transient addresses. These addresses are assigned and reclaimed dynamically within applications. Administratively scoped multicast address space is divided into the Iollowing scopes: Local scope (239.255.0.0/16 and grows downward to 239.254.0.0/16, 239.253.0.0/16) Organization local scope (239.192.0.0/14 with possible expansion to ranges 239.0.0.0/10, 239.64.0.0/10, and 239.128.0.0/10) Parts oI a global scope are also used Ior new protocols and temporary usage. 224.1.0.0-224.1.255.255 Experimental Internet Stream Protocol (ST) version 2 Multicast Groups224.2.0.0-224.2.127.253 Multimedia ConIerence Calls 224.2.127.254 Session Announcement Protocol (SAP) v1 Announcements 224.2.127.255 SAPv0 Announcements (deprecated) 224.2.128.0-224.2.255.255 SAP Dynamic Assignments 224.252.0.0-224.255.255.255 Distributed Interactive Simulation (DIS) transient groups 232.0.0.0-232.255.255.255 Versatile Message Transaction Protocol (VMTP) transient groups 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 50IP MuIticast Basic Addressing (cont.)IP MuIticast Basic Addressing (cont.) Transient addresses, assigned and recIaimed dynamicaIIy (within appIications) GIobaI range: 224.0.1.0-238.255.255.255 224.2.x.x usuaIIy used in Mbone appIications Limited (IocaI) scope: 239.0.0.0/8 - "private IP muIticast addresses" - RFC-2365 Site-IocaI scope: 239.253.0.0/16 Organization-IocaI scope: 239.192.0.0/14 Part of a gIobaI scope recentIy used for new protocoIs and temporary usageCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-47 One oI the methods Ior static address allocation Ior multicast groups is deIined in Internet standard RFC 2770 titled 'GLOP Addressing in 233/8: Until Multicast Address Set-Claim (MASC) has been Iully speciIied and deployed, many content providers oI the Internet require something at the very least to begin address allocation. This necessity is being addressed with a temporary method oI static multicast address allocation.

The basic concept behind this methodology is as Iollows: Use the 233/8 address space Ior static address allocation. The middle two octets oI the group address would contain your autonomous system (AS) number. The Iinal octet is available Ior group assignment. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 51RFC 2770 Addressing RFC 2770 Addressing Static Group Address Assignment for Interdomain MuIticast Temporary method to meet immediate needs Group range: 233.x.x.0 - 233.x.x.255 AS number is inserted in middIe two octets (x.x) Remaining Iow-order octet used for group assignment within a domain Defined in IETF draft "draft-ietf-mboned-gIop-addressing-xx.txt"2-48 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. The growth in demand Ior interdomain multicast routing led to some interim solutions such as GLOP. The problem with GLOP addressing is in a relatively low number oI available groups within a certain domain represented as an AS number. Only the last byte is available, which results in 255 uniquely identiIied groups only. There are several situations where the sources (senders) have to be globally known. A special range oI multicast addresses was dedicated Ior those servers and a special multicast protocol is in development Source SpeciIic Multicast (SSM). This development will always allow the building oI the distribution tree rooted at the source Ior any group address Irom the range 232.0.0.0/8 (232.0.0.1 232.255.255.255). 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 52Source Specific MuIticast Addressing Source Specific MuIticast Addressing Group Address Assignment for Interdomain MuIticast Used excIusiveIy for gIobaIIy known sources and source-specific distribution trees (across domains) Group range: 232.0.0.0/8 Defined in IETF draft "draft-hoIbrook-ssm-00.txt"Copyright 2003, Cisco Systems, nc. P Multicast Technology 2-49 The scalability in multicast address allocation can only be achieved with dynamic group address assignment methods: SDR This was typically accomplished using the SDR application, which detects collisions in an IP multicast group address assignment at the time new sessions were being created and to pick an unused address. Although it was suIIicient Ior use on the old Mbone when the total number oI multicast sessions in the Internet was quite low, SDR has severe scaling problems that preclude it Irom continuing to be used as the number oI sessions increase. MASC: MASC is a new proposal Ior a dynamic multicast address allocation that is being developed by the Multicast-Address Allocation (malloc) Working Group oI the Internet Engineering Task Force (IETF). This new proposal will provide Ior dynamic allocation oI the global IP multicast address space in a hierarchical manner. In this proposal, domains lease IP multicast group address space Irom their parent domain. These leases are good Ior only a set period. It is possible that the parent domain may grant a completely diIIerent range at lease renewal time because oI the need to reclaim address space Ior use elsewhere in the Internet. This is a very nontrivial mechanism and Iar Irom actual implementation. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 53Dynamic MuIticast Addressing Dynamic MuIticast Addressing AccompIished using SDR appIication (Mbone) Sessions/groups announced over weII-known muIticast groups (e.g. 224.2.127.254) Address coIIisions detected and resoIved at session creation time - Iookup into an SDR cache Not scaIabIe Future dynamic techniques in deveIopment MuIticast Address Set-CIaim (MASC) HierarchicaI, dynamic address aIIocation scheme ExtremeIy compIex garbage-coIIection probIem Not avaiIabIe yet (draft-ietf-maIIoc-masc-01.txt)2-50 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. MASC is only a part oI a hierarchical Multicast Address Allocation Architecture (MAAA) and represents the top level oI the architecture. When a certain range oI multicast addresses is allocated at the top level, the underlying hierarchies use additional protocols Ior address assignment. On a domain lavel (Ior example, service provider) the protocol is Address Allocation Protocol (AAP). Recently, additions/modiIications to the traditional Dynamic Host ConIiguration Protocol (DHCP) protocol enabled address assignments Ior multicast purposes also. One oI the approaches is Multicast Address Dynamic Client Allocation Protocol (MADCAP), which allows address assignment at leaI segments where multicast sources actually reside. Servers Ior address allocation within the MAAA architecture are Multicast Address Allocation Servers (MAAS). 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 54Dynamic MuIticast Addressing (cont.)Dynamic MuIticast Addressing (cont.) MAAA - MuIticast Address AIIocation Architecture - hierarchicaI architecture MASC - MuIticast Address Set CIaim - top-IeveI address aIIocation protocoI AAP - Address AIIocation ProtocoI - within a domain MADCAP - MuIticast Address Dynamic CIient AIIocation ProtocoI - on Ieaf segments MAAS - MuIticast Address AIIocation ServersCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-51 SummaryUpon completing this lesson, you must be able to: Explain how the multicast address range is split into various Iunctional groupings. List IP multicast address assignment methods that exist or are in development. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 55Summary Summary After compIeting this section, the student shouId be abIe to: ExpIain how the muIticast address range is spIit into various functionaI groupings List IP muIticast address assignment methods that exist or are in deveIopment2-52 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Review Questions What determines an IP multicast address? Which range oI IP multicast addresses is considered as private? Which range oI IP multicast addresses is reserved? Which address ranges are dedicated Ior interdomain multicast routing? List the mechanisms (existing and in development) Ior address assignment. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 56Review Questions Review Questions What determines an IP muIticast address? Which range of IP muIticast addresses is considered as "private"? Which range of IP muIticast addresses is reserved? Which address ranges are dedicated for interdomain muIticast routing? List the mechanisms (existing and in deveIopment) for address assignment.Copyright 2003, Cisco Systems, nc. P Multicast Technology 2-53 MuIticast Sessions - Directory Services ObjectivesUpon completion oI this lesson, you will be able to: Explain how receivers get multicast data Irom sources. List the methods oI multicast session announcement. Describe the issues associated with typically unknown populations oI multicast receivers. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 58Objectives ObjectivesUpon compIetion of this section, the student wiII be abIe to: ExpIain how receivers get muIticast data from sources List the methods of muIticast session announcement Describe the issues associated with a typicaIIy unknown popuIation of muIticast receivers2-54 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Whenever a multicast application is started on a receiver, the application has to know which multicast group to ioin. The application has to learn about the available sessions/streams, which typically map to one more IP multicast groups. These are several possibilities Ior applications to learn about the sessions: The application may ioin a well-known, predeIined group, to which announcements about available sessions are done. Some type oI directory services is available, and the application may contact the appropriate directory server. The application may be launched Irom a web page on which the sessions are listed as URLs: even e-mail may be used. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 59Learning About MuIticast SessionsLearning About MuIticast Sessions PotentiaI receivers have to Iearn about muIticast streams / sessions avaiIabIe before muIticast appIication is Iaunched PossibiIities: Another muIticast appIication sending to a weII-known group whose members are aII potentiaI receivers Directory services Web page, e-maiI, and so onCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-55 In MBONE, the session directory (sd) application served as a means Ior announcing available sessions and to assist in creating new sessions. The Initial sd tool was revised resulting in the sdr (Session Directory Protocol) tool. Sdr is an applications tool that allows the Iollowing: Session description and its announcement Transport oI session announcement via well-known multicast groups (224.2.127.254) Creation oI new sessionsWhen sdr is used at the receiver side, it is used Ior receivers to learn about available groups / sessions.When sdr is used at the sender side, it is used to create new sessions and to avoid address conIlicts. Senders at the time oI session creation consult their respective sdr caches (senders are also receivers) and choose one oI the unused multicast addresses. When the session is created, the senders start announcing it with all the inIormation that is needed by receivers to successIully ioin the session. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 60Mbone SDR Mbone SDR Mbone uses sd (Session Directory) and an enhanced version sdr Sdr is a session description protocoI and transport mechanism Sdr is used by sources for assigning new muIticast addresses Checks the sdr cache to avoid confIicts Creates a session and sends its description via sdr announcements (224.2.127.254)2-56 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. The window on the leIt shows an example oI the SDR application in action. Each line is a multimedia session that has been created by some user in the network and is being announced (via multicast) by the SDR application oI the creator. By clicking on one oI these sessions, the window on the right is activated. This window displays various inIormation about the multimedia session including the Iollowing: General session inIormation Session schedule Media type (in this case audio and video) Media Iormat Multicast group and port numbers Using the window on the right, you may have SDR launch the appropriate multicast application(s) to ioin the session 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 61Mbone SDR (cont.) Mbone SDR (cont.)Copyright 2003, Cisco Systems, nc. P Multicast Technology 2-57 The Irequency oI SDR announcements depends on the number oI sessions to be announced and on the bandwidth oI the outgoing interIace through which the announcement will be sent. The number oI sessions/bandwidth is kept at a constant value. Typical values are in the range oI a Iew minutes (5 to 10). Generally, sessions may be announced by anyone the inIormation on the source oI the session is included in the SDR contents.One oI the problems inherent to session announcement is a late ioin latency problem. Potential receivers that miss the announcement have to wait Ior the next one (and they are rare). SDR caching mechanisms may improve the ioin latency. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 62Mbone SDR (cont.) Mbone SDR (cont.) The frequency of announcements Depends on the number of sessions and avaiIabIe bandwidth The ratio is kept aImost constant Sessions can be announced by anyone -the source is part of a session description InitiaI Iatency probIem - new receivers have to wait for next announcement2-58 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. Sdr caching is used to decrease the initial ioin latency. As soon as a multicast application is started at the receiver side, the caches are inspected and ioin the selected session/multicast group initiated. Note t is not necessary that a session that appears in an announcement and is stored in a cache be active at the moment. Session announcements are sent whenever a session is created and periodically. The creation of the session does not necessarily mean that that session is activated at the moment and that any streaming appears. One of the fields in a session description is used for providing information on the session schedule. Cisco routers can also cache the SDR inIormation, but they do not act as an SDR proxy (to allow late ioiners to decrease the latency). The only purpose oI SDR caching in Cisco routers is to use the cached inIormation in more descriptive outputs (Ior example, instead oI a multicast group address the session name may be presented). 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 63InitiaI Join Latency InitiaI Join Latency Because of infrequent announcements, caching mechanisms are used NewIy joined receivers consuIt their caches and do not need to wait for the next announcement Cisco routers can cache sdr announcements Not used to decrease join Iatency Used for more descriptive show outputsCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-59 Initial eIIorts in the mechanisms Ior session announcements resulted in an RFC 2327, which deIines an SDR Session Description Protocol. The only purpose oI this RFC is to deIine the standard set oI variables that describe the sessions. Most oI those variables were inherited Irom the sdr tool. The transport itselI is not deIined in this RFC. The packets describing the session may be transported across the multicast enabled network via several mechanisms. Session Announcement Protocol (SAP), which is deIined in RFC 2974 and carries the session inIo. Session Initiation Protocol (SIP), which is deIined in RFC 2543, is a signaling protocol Ior Internet conIerencing, telephony, presence, events notiIication, and instant messaging. Real Time Streaming Protocol (RTSP), which is deIined in RFC 2326 and serves mainly as a control protocol in a multimedia environment: RTSP allows VCR-like controls (select, Iorward, rewind, pause, stop, and so on) and also carries inIormation on a session. E-mail (in MIME Iormat) may also carry SDR packets describing the session. Web pages may provide session descriptions in standardized SDR Iormat also. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 64New Methods of Session AnnouncementsNew Methods of Session Announcements Session Description ProtocoI (SDR) defined in RFC 2327 - severaI fieIds Transport can be: Session Announcement ProtocoI (SAP) Session Initiation ProtocoI (SIP) ReaI-Time Streaming ProtocoI (RTSP) -defined in RFC 2326, for VCR-Iike controIs E-maiI (MIME format) Web (HTTP)2-60 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. The SDR mechanisms are shown through the sample IP multicast application. Cisco IP/TV is used, and generally three components exist: Server (the source) Content manager (the 'directory server) Viewer (the receiver) The viewers may either: Contact the content manager directly (by unicast) and request the list oI available programs (sessions, streams) Irom it. Listen to periodic SAP announcements. The standard SDR Iormat Ior session description is used. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 65A Cisco IP/TV ExampIe A Cisco IP/TV ExampIe Cisco IP/TV AppIication CIients (Viewers) use Program Listing Contact the server directIy Listen to SAP announcementsCopyright 2003, Cisco Systems, nc. P Multicast Technology 2-61 The slide shows a sample output Irom a session description in an SDR Iormat. It is possible to determine that the described session is the Iollowing: The session is live. The session components are sent at a rate oI 512 kbps and 5 Irames/s. The session is composed oI video and audio. Video is sent to multicast group/port 224.2.1.1/32233. Audio is sent to multicast group 224.2.27.6/55123. Source IP address is 192.168.1.1. Sessions TTL (range) is 16. There are several other Iields in a description, including the session schedule, the session media encoding, and so on. 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 66SDR Contents SDR Contents(...aliveabandwidth.SI?aframerate.Smvideo video ?? RTP/AVP ? I 98maudio audio SSI? RTP/AVP I4 0 S 98 9I 98 99 I00 I0I I0? I0o- IS9S 0 IN IP4 I9?.I88.I.IcvideoIN IP4 ??4.?.I.I/I8caudioIN IP4 ??4.?.?I.4/I8(...The live session is composed of video and audio media sent to multicast group / port 224.2.1.1/32233 and 224.2.27.6/55123 respectively from the source 192.168.1.1 with TTL 16 and at a rate of 512 kbits/s.(...aliveabandwidth.SI?aframerate.Smvideo video ?? RTP/AVP ? I 98maudio audio SSI? RTP/AVP I4 0 S 98 9I 98 99 I00 I0I I0? I0o- IS9S 0 IN IP4 I9?.I88.I.IcvideoIN IP4 ??4.?.I.I/I8caudioIN IP4 ??4.?.?I.4/I8(...The live session is composed of video and audio media sent to multicast group / port 224.2.1.1/32233 and 224.2.27.6/55123 respectively from the source 192.168.1.1 with TTL 16 and at a rate of 512 kbits/s.2-62 mplementing Cisco Multicast (MCAST) v1.0 Copyright 2003, Cisco Systems, nc. As described, the session originators are known to receivers via session announcement mechanisms. Sometimes the receiver population has to be known also to sources. This Iact applies to conIerencing applications (where all receivers are sources at the same time) or to environments that require either oI the Iollowing: Enhanced security Adaptability to the quality oI the network: Ior example, poor reception quality at the receiver side triggers diIIerent encoding at the sender One oI the mechanisms through which some Ieedback on receivers may be learned is the control (RTCP) component oI the RTP (Real-Time Transport Protocol). RTCP provides the senders with inIormation on the receiver identiIication and on the quality oI reception. The inIormation Irom receivers may be returned to the senders either via unicast or multicast (needed especially in a conIerencing environment). 2000, Cisco Systems, Inc. www.cisco.com IP MuIticast Primer Chapter 2 Page 67The ProbIem of Unknown Receiver PopuIationThe ProbIem of Unknown Receiver PopuIation The Iack of mechanisms for receiver identification AppIications using RTP have buiIt-in capabiIity via RTCP Some appIications use unicast for return path messages Receivers generaIIy need not to be known Exception: when feedback is needed (because of quaIity or security reasons)Copyright 2003, Cisco Systems, nc. P Multicast Technology 2-63 SummaryUpon complet