Interdomain Multicast Routing is a book on the timely technology of multicasting and is written, mainly, for network engineers responsible for configuring and maintaining that capability within their networks. It is a practical reference guide that includes Cisco Systems and Juniper Networks technology. The authors' goals are to explain the rationale and benefits of multicast routing on the Internet, to include the two leading vendors of routers and routing technology and note how they differ when applying interdomain multicast routing (IMR), and to explain the underpinnings of interdomain multicasting in simple, clear language. For a preview of the topics within this book, the following chapter listings detail the topic matter.
Chapter 1, "Interdomain Multicast Fundamentals," begins with a definition of multicast transmisson of data in contrast to other means of data delivery, within and outside the Internet, and then provides an introductory explanation of some of the issues affecting successful routing of multicast traffic on the Internet. Those seeking to understand the enormous potential for multicast may wish to tune in directly to this section.
Chapter 2, "IMR Overview," is a general description of how to generate and receive multicast traffic, including a description of methods for routers to detect sources and receivers of multicast traffic. The discussion then proceeds from multicast single-domain routing using PIM-SM (Protocol Independent Multicast-Sparse Mode) to interdomain multicast routing using MSDP (Multicast Source Discovery Protocol).
Chapter 3, "Multicast Routing Protocols," examines the two primary types of multicast routing protocols, describing the main features and examples of each.
Chapter 4, "Protocol Independent Multicast-Sparse Mode (PIM-SM)," lays out PIM-SM, the predominant multicast routing protocol for interdomain routing. Since PIM-SM is commonly used in the initial sequence of activities that gets multicast up and running within a single domain, the procedure dominates the scope of this chapter. PIM messages for both version 1 and version 2 of the protocol are covered, as is the use of anycast rendezvous point (RP) to improve load balancing and redundancy. Ample diagrams and corresponding examples describe distribution tree construction and teardown for various topologies, and the chapter ends with a discussion of multicast scoping.
Chapter 5, "Multicast Source Discovery Protocol (MSDP)," demonstrates how to use MSDP to connect multiple PIM-SM domains and subdomains. MSDP is an any source multicast (ASM) mechanism for giving Internet multicast routing its "interdomain" reach. This chapter contains a number of illustrations of the rules that determine the reverse path forwarding (RPF) peer, a critical component in MSDP. Recognizing the paucity of clear information about MSDP peer-RPF rules, which are quite complex, the authors have provided detailed rule descriptions, as well as diagrams and realistic examples. The intent is for Chapter 5 to become the most definitive guide available on the subject (MSDP peer-RPF rules). The chapter concludes with sections on mesh groups, susceptibility to operational problems, and a discussion of the prospects for the widely used MSDP vis a vis the upcoming version of Border Gateway Multicast Protocol (BGMP).
Chapter 6, "Source-Specific Multicast (SSM)," is a critical component of the book. SSM, a recent addition to the ever-changing multicast routing landscape, holds the greatest amount of promise for deployment, considering that many believe the most dominant commercial use of Internet multicast will likely conform to a one-to-many model. This chapter explains the rationale for development of this SSM service model versus ASM and how SSM can serve as a basis for learning the more complex world of ASM.
Chapter 7, "Multiprotocol Extensions for BGP (MBGP)," and Chapter 8, "Multitopology Routing in Intermediate System to Intermediate System (M-ISIS)," focus on how to create two separate virtual topologies, one for unicast and one for multicast. MBGP and M-ISIS can be used side-by-side to build a dedicated multicast RPF table, just as BGP and ISIS have traditionally coexisted in unicast intra-AS and inter-AS environments.
The remaining chapters of Interdomain Multicast Routing cover critical hands-on, real-world examples and tools. Chapter 9, "Configuring and Verifying Multicast Routing on Juniper Networks Routers," and Chapter 10, "Configuring and Verifying Multicast Routing on Cisco Systems Routers," provide practical methods and guidelines for actually configuring and verifying multicast routing on Juniper Networks and Cisco Systems routers.
Chapter 11, "Case Study: Service Provider Native Deployment," provides a representative case study for native deployment of IMR by an Internet service provider; Juniper Networks and Cisco Systems router configurations for all router roles in this example network are also set forth.
Chapter 12, "Management Tools for Multicast Networks," discusses management tools for multicast networks, chiefly Simple Network Management Protocol (SNMP) and the mtrace facility for IP multicast.
Chapter 13, "Other Related Topics," covers topics such as the development of BGMP incorporating Multicast Address Set Claim (MASC) protocol mapping, bidirectional PIM, and use of real-time transport protocol (RTP) for host-to-host transport over IP networks. RTP is suited to real-time applications such as video and audio streaming.
The Appendixes list packet formats for Internet Group Management Protocol (IGMP), PIM, and MSDP.
Finally, because any new world of knowledge comes to be mastered only by intelligent use and definition of its key concepts, we spent a considerable amount of time gathering and refining pertinent terminology; we hope the Glossary clarifies key abbreviations, acronyms, and definitions and even serves to stimulate dialog leading to more exact rendering of terms in future iterations of the book.
Brian Edwards,
Leonard Giuliano,
Brian Wright
January 2002
0201746123P04022002