Creating Multicast Vpns Using The Data Mdt; Data Mdt Sources - Juniper JUNOSE 11.0.X MULTICAST ROUTING Configuration Manual

Creating Multicast VPNs Using the Data MDT

A data multicast distribution tree (MDT), based on section 8 of Internet draft
draft-rosen-vpn-mcast-08.txt, Multicast in MPLS/BGP IP VPNs, solves the problem of
P routers flooding unnecessary multicast information to PE routers that have no
interested receivers for a particular VPN multicast group. The data MDT solution
requires the creation of a new tunnel by the PE router if the source exceeds a
configured rate threshold parameter. All other PE routers join the new tunnel only
if the PE router has receivers in the VPN for that multicast group.
The JUNOSe software uses dynamic point-to-multipoint GRE tunnels to configure
data MDTs. In the current release, IPv6 transport over GRE (unicast or multicast) is
not supported. For more information, see Configuring Dynamic IP Tunnels in the
JUNOSe IP Services Configuration Guide.
Data MDTs are established using PIM-SM (shared RP Trees) and PIM-SSM (Source
Trees). Profiles for dynamic interfaces in the VRF are restricted to sparse-mode only.

Data MDT Sources

A C-SG flow arriving in the source VRF is a candidate for a data MDT if the system
matches the C-SG in the route map that you specify for the data MDT using the ip pim
data-mdt command. The C-SG flow is initially forwarded on the default MDT. The
system creates the data MDT when the flow rate exceeds a value you configure in
the route map using the set threshold command.
When the Source C-PIM-SM first creates a data MDT for a C-SG flow, it sends a <C-SG,
P-G> MDT join message with type, length, value (TLV) format to the default MDT.
This message invites peer PE routers to join the new data MDT. It starts a timer that
you can configure using the mdt-data-delay command to track the number of seconds
before switching to the data MDT. When that timer expires, C-PIM-SM switches from
sending C-SG data on the default MDT to sending data on the data MDT.
When the C-SG flow is switched to the data MDT, the Source C-PIM-SM starts a timer
that you can configure using the mdt-data-holddown command to track the number
of seconds before switching to the default MDT. When the timer expires, the data
MDT is deleted and the C-SG flow switched back to the default MDT if the flow rate
drops back below the threshold. If the flow rate exceeds the threshold, the timer
restarts. If the timer expires and the flow rate is below the threshold, the data MDT
is removed.
The Source C-PIM-SM maintains sent MDT Join TLV messages in its database as long
as they are active. While the data MDT is active, C-PIM-SM resends that MLD Join
TLV message using a setting that you can configure using the mdt-interval command
to measure time in seconds between successive MLD join TLV messages.
host1(config-if)#tunnel mdt
The no version disables MDT on the interface.
See tunnel mdt.
Chapter 3: Configuring PIM for IPv4 Multicast
Creating Multicast VPNs
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