Home > Articles > Multicast Design Solutions

Multicast Design Solutions

Chapter Description

In this sample chapter from IP Multicast, Volume II: Advanced Multicast Concepts and Large-Scale Multicast Design, you will examine several archetypical network design models and best practices for multicast deployments.

Service Provider Multicast

Service provider multicast message transport falls into two categories: infrastructure multicast, used for delivering services, and customer multicast packet transport. Multicast that supports the provider infrastructure enables the provider to offer services to customers—such as multicast VPNs (MVPNs) (discussed in Chapter 3) and multitenant data center services (discussed earlier in this chapter and in Chapter 4). The provider infrastructure may also use multicast for content services. Internet multicast services is one example. In addition, many providers use multicast to deliver television content over their networks, where the set-top box is a multicast client, and channel content is delivered over specific groups.

Today, relatively few multicast applications are transported across the Internet natively. Most service providers have yet to embrace the benefits of transporting multicast, primarily due to the complexity and the ability to charge for multicast services. For SPs that have enabled and are using multicast, kudos to you! Chapters 1, 3, and 4 are very helpful for creating multicast-enabled provider infrastructure. In addition, there are a few design elements to consider when deploying multicast services in a provider network, as discussed in the following sections.

Service Provider PIM-Type Selection and RP Placement

The most important decisions that service providers have to make are similar to the decisions required for multitenant data centers: What mode of PIM needs to be selected, and where should RPs be placed? Chapter 3 discusses the numerous options that service providers use to transport multicast messages using MPLS, since using MPLS is currently the preferred method of moving both unicast and multicast messages across a shared service cloud. Remember that to deploy an MPLS service that supports multicast, the provider network needs a multicast-enabled core network that supports multicast data trees (MDTs).

The provider multicast domain that services the MDTs is completely isolated from any customer domains. This means the provider network needs to choose a PIM method (ASM or SSM) and, if necessary, configure RPs for the network. Service provider network architects should consider using SSM as the infrastructure delivery method. It greatly simplifies the multicast deployment at scale. SSM does not require an RP and has a separate and specific multicast range,, that is easy to scope and manage. Examine the network diagram in Figure 5-23. This network provides an MPLS MVPN service to the customer between Site 1 and Site 2. The customer is using PIM-SM and is providing its own RP on the customer premises equipment router at Site 1. The provider network is using SSM to transport the MDT for the customer VPN with route distinguisher (RD) 100:2.

Figure 5-23

Figure 5-23 SSM Provider Infrastructure Domain

Using SSM also simplifies scaling across global networks and eases the burden of converting merged autonomous systems from network acquisitions, as interdomain routing is a natural amenity of SSM. In addition, the same SSM domain can be used to provide content services within the infrastructure. Or, if needed, the SSM domain can coexist with a PIM-SM domain when required.

Remember that to implement SSM, any clients need to support IGMPv3. Cisco IOS-XR service provider software supports SSM delivery for MPLS MVPNs natively. The MVPN configuration requires a specific source and group for MDT. Simply use an SSM group range for MDT configurations and enable the transport interfaces with PIM-SM. Example 5-2 shows the relevant configuration of PE1 from Figure 5-23 to enable SSM and the MDT in IOS-XR.

Example 5-2 MDT SSM Configuration Using IOS-XR

RP/0/RP0/CPU0:PE1# configure
RP/0/RP0/CPU0:PE1(config)# multicast-routing
RP/0/RP0/CPU0:PE1(config-mcast-ipv4)# interface all enable
RP/0/RP0/CPU0:PE1(config-mcast-ipv4)# mdt source Loopback 0
RP/0/RP0/CPU0:PE1(config-mcast-default-)# vrf Customer
RP/0/RP0/CPU0:PE1(config-mcast-vrf_A-ipv4)# mdt default
RP/0/RP0/CPU0:PE1(config-mcast-vrf_A-ipv4)# mdt data threshold 1200
RP/0/RP0/CPU0:PE1(config-mcast-ipv4)# exit
RP/0/RP0/CPU0:PE1(config)# router igmp
RP/0/RP0/CPU0:PE1(config-igmp)# version 3
RP/0/RP0/CPU0:PE1(config)# commit

For customers interested in these services, purchasing multicast transport from an SP is something of a premium service—that is, service providers usually charge an additional fee. If you are purchasing L2 VPN services that a service provider offers using Virtual Private LAN Service (VPLS), Provider Backbone Bridging combined with Ethernet VPN (PBB-EVPN), or a Pseudowire service, there is a better chance that multicast transport services are offered. The transport of multicast messages is often limited to a certain rate. If more bandwidth is required, you can overcome the limitation by purchasing additional bandwidth or encapsulating multicast messages using some sort of overlay technology, such as MVPN, GRE, and so on.

Service provider networks that want to also provide content services over the same infrastructure may not be able to choose SSM if the set-top box or other clients do not support IGMPv3. In such cases, PIM-SM is the preferred alternative for the provider infrastructure, and the provider network should either use static RP mappings or redundant Anycast RP for added reliability. Figure 5-24 shows the same provider network as Figure 5-23, but this time using PIM-SM.

Figure 5-24

Figure 5-24 PIM-SM Provider Domain

When a provider grows beyond the ability to support every customer in a single routed domain, BGP confederations or even multiple public domains are often used to carry traffic. Remember from Chapter 1 that using multiple IGP and BGP domains for unicast requires corresponding multicast domains, with interdomain routing, to complete multicast transport across the network. In such situations, providers should consider nesting RPs, using anycast for redundancy, and building a mesh of MSDP peerings between them. This completes the transport across the provider domain. Figure 5-25 shows a very high-level diagram of this type of provider multicast domain design.

Figure 5-25

Figure 5-25 Interdomain Infrastructure Transport

For networks that also provide multicast services to customers, there are other considerations. In particular, IP Television (IPTV) delivery requires some unique design elements, which are discussed next.

IPTV Delivery over Multicast

Figure 5-26 provides a 10,000-foot view of the components of multicast in the cable environment.

Figure 5-26

Figure 5-26 High-Level Cable TV Multicast Network

There are three main architectural components in an IPTV multicast delivery service:

  • Service plane: Consists of the IPTV source, IPTV multicast service gateway, and IP Multicast receiver

  • Service interface: Consists of the signaling mode between the service plane and the network plane

  • Network plane: Consists of IP network configuration to support multicast (control and data plane), resiliency, and high availability of the network transport

The network consists of a shared platform needed for all services, like QoS (DiffServ or RSVP based on applicability) or QoS-based Call Admission Control (CAC) systems for transport of multiple types of content. IP Multicast gateways consists of ad splicers, converters, and so on.

The choice of multicast transport protocols should determine the service plane communication needs of connected devices. Based on protocol requirements for the content providers, such as CAC, IGMPv3 or v2 support, and application redundancy, the multicast network technology selected for the transport layer should be able to support all required application services. The WAN technology generally consists of an MPLS L3 VPN or L2 VPN solution that connects to the end host access technology. Layer 2 Pseudowire could also be considered using a protected Pseudowire deployment. This provides subsecond convergence by leveraging features such as Fast Reroute (FRR) with RSVP-TE LSPs. It also provides the network operators service level agreement (SLA) guidelines for multicast transport. The items to consider in the design are as follows:

  • The need for global, national, or regional content sources

  • Fast convergence and availability

  • Requirements for different media content

Other factors to keep in mind during the design stage relate to the type of feed. The feed could be any or all of the following:

  • Broadcast feed: Including static forwarding to a DSLAM

  • Switched digital video: Static PIM tree to the PE-AGG router

  • Multicast based video: Dynamic path creation to the end receiver

These three types of video feed are illustrated in Figure 5-27.

Figure 5-27

Figure 5-27 Three Types of Video Feed

The service interface consideration in this section includes multicast signaling support with IGMPv3, applications built to SLA requirements, and applications built using CAC methods. The PIM-SSM model generally fits this design, with one-to-many communication building on any individual sources. This method is best suited to handling join/prune latency requirements. PIM-SSM will also help with the localization of services based on unicast IP addresses of different host servers using the same multicast group. Techniques using different masks for source IP addresses can be used for redundancy for the source of the multicast service. SSM multicast technology can be aligned with channel feeds, and source IP address spoofing is mitigated based on built-in application support for IGMPv3. The transport design also covers path separation across the WAN transport segment.

It is critical to understand multicast VLAN registration (MVR) and the features in the cable environments. MVR is designed for multicast applications deployed in Ethernet ring-based service provider networks. The broadcast of multiple television channels over a service provider network is one typical example. MVR allows a subscriber on a port to subscribe and unsubscribe to a multicast stream on the networkwide multicast VLAN, thereby enabling a single multicast VLAN to be shared in the network while subscribers (receivers) remain in separate VLANs. It also optimizes stream delivery by providing the ability to send continuous multicast streams in the multicast VLAN rather than send separate streams from the subscriber VLANs.

MVR assumes that subscriber ports subscribe and unsubscribe to these multicast streams by sending IGMPv2 join and leave messages on the VLAN. MVR uses IGMP snooping, but MVR and IGMP snooping can be enabled or disabled without impacting each other. The MVR feature only intercepts the IGMP join and leave messages from multicast groups configured under MVR. The MVR feature has the following functions:

  • Categorizes the multicast streams configured under the MVR feature and ties the associated IP Multicast group in the Layer 2 forwarding table

  • Modifies the Layer 2 forwarding table to include or exclude the receiver of the multicast stream (not constrained by VLAN boundaries)

The MVR has two port types:

  • Source: Configures a port that receives and sends multicast data as source ports. Subscribers cannot be directly connected to source ports; all source ports on a switch belong to the single multicast VLAN.

  • Receiver: Configures a port as a receiver port and only receives multicast data.

Cisco Press Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Cisco Press products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@ciscopress.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by Cisco Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.ciscopress.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020