Cisco ASR 9000 Series Software Manual page 17

Implementing Layer-3 Multicast Routing on Cisco IOS XR Software
PIM-Bidir is not supported on MVPN.
Note
There are two ways MCAST VPN traffic can be transported over the core network:
• Rosen GRE (native): MVPN uses GRE with unique multicast distribution tree (MDT) forwarding to
enable scalability of native IP Multicast in the core network. MVPN introduces multicast routing
information to the VPN routing and forwarding table (VRF), creating a Multicast VRF. In Rosen GRE,
the MCAST customer packets (c-packets) are encapsulated into the provider MCAST packets (p-packets),
so that the PIM protocol is enabled in the provider core, and mrib/mfib is used for forwarding p-packets
in the core.
• MLDP ones (Rosen, partition): MVPN allows a service provider to configure and support multicast
traffic in an MPLS VPN environment. This type supports routing and forwarding of multicast packets
for each individual VPN routing and forwarding (VRF) instance, and it also provides a mechanism to
transport VPN multicast packets across the service provider backbone. In the MLDP case, the regular
label switch path forwarding is used, so core does not need to run PIM protocol. In this scenario, the
c-packets are encapsulated in the MPLS labels and forwarding is based on the MPLS Label Switched
Paths (LSPs) ,similar to the unicast case.
In both the above types, the MVPN service allows you to build a Protocol Independent Multicast (PIM) domain
that has sources and receivers located in different sites.
To provide Layer 3 multicast services to customers with multiple distributed sites, service providers look for
a secure and scalable mechanism to transmit customer multicast traffic across the provider network. Multicast
VPN (MVPN) provides such services over a shared service provider backbone, using native multicast
technology similar to BGP/MPLS VPN.
In addition to all the ethernet based line cards, Multicast VPN is also supported on the Cisco ASR 9000 Series
SPA Interface Processor-700 card from the Cisco IOS XR Software Release 4.0 onwards. Cisco ASR 9000
Series SPA Interface Processor-700 enables the Cisco ASR 9000 Series Routers to support multiple legacy
services (such as TDM and ATM) on a router that is primarily designed for Ethernet networks. Cisco ASR
9000 Series SPA Interface Processor-700 is QFP-based and therefore has the flexibility and service scale
offered by Cisco ASIC and the reliability of Cisco IOS XR Software.
MVPN emulates MPLS VPN technology in its adoption of the multicast domain (MD) concept, in which
provider edge (PE) routers establish virtual PIM neighbor connections with other PE routers that are connected
to the same customer VPN. These PE routers thereby form a secure, virtual multicast domain over the provider
network. Multicast traffic is then transmitted across the core network from one site to another, as if the traffic
were going through a dedicated provider network.
Multi-instance BGP is supported on multicast and MVPN. Multicast-related SAFIs can be configured on
multiple BGP instances.
Multicast VPN Routing and Forwarding
Dedicated multicast routing and forwarding tables are created for each VPN to separate traffic in one VPN
from traffic in another.
The VPN-specific multicast routing and forwarding database is referred to as MVRF. On a PE router, an
MVRF is created when multicast is enabled for a VRF. Protocol Independent Multicast (PIM), and Internet
Group Management Protocol (IGMP) protocols run in the context of MVRF, and all routes created by an
MVRF protocol instance are associated with the corresponding MVRF. In addition to VRFs, which hold
Cisco ASR 9000 Series Aggregation Services Router Multicast Configuration Guide, Release 5.1.x
Multicast VPN
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