Configuring Hardware Multicast Packet Replication - Juniper JUNOSE 11.0.X MULTICAST ROUTING Configuration Manual

Chapter 5: Configuring IPv6 Multicast
information, see Configuring Ethernet Interfaces in JUNOSe Physical Layer
Configuration Guide.
The regular multicast implementation utilizes interface stacking that provides a
unique IPv6 attachment point for each elaboration of the egress multicast packet.
For the hardware multicast packet replication feature, you must attach policies
to an interface stack over port 8 that defines the encapsulation of the egress
multicast traffic. The system supports policies over port 8 just as it is above any
of the other ports on this line module.
Policies applied to the interface stack over port 8 affect the packets traversing
this stack whether or not the packet is destined for one port or all of the physical
ports. Therefore, you cannot apply different egress policies to multicast traffic
for the interfaces stacked above different ports, or rate limit on an individual
interface over a port. You also cannot monitor policy statistics on individual
interfaces over a port.
Instead, you can apply egress policy to an interface stacked over port 8. The
system applies the policy before the packet has been elaborated for each of the
ports.
The JUNOSe QoS component provides hierarchical egress scheduling and shaping
on Gigabit Ethernet ports 0–7. The regular multicast implementation replicates
packets on the FC, with each replicated packet placed on a line module queue
destined for a single physical port. The line module queue can also receive QoS
behavior specific to that queue.
For the hardware multicast packet replication feature, the FC does not replicate
the packet for each of the individual ports. Instead, it places the packet on a
special queue destined for port 8.
You can configure QoS on the packets flowing through port 8, but this has limited
value because each packet passed through this port can be transmitted through
one of more of the physical ports. Therefore, the packets placed on this special
queue might not receive the same QoS behavior as ports 0–7.
We recommend that you configure the network so the I/O or IOA queues are
not oversubscribed. The traffic transmitted by the physical port is a combination
of packets from the two I/O or IOA queues. When the sum of the packets in these
queues is greater than line rate, the system can drop traffic that is not using
hardware multicast packet replication.
When you configure a traffic shaper on a physical port and configure hardware
multicast packet replication, the packets created using the feature avoid the
traffic shaper for that port. To control this, you can use traffic shaper on the
physical port and port 8. The sum of the traffic shapers must be less than or
equal to the line rate of the port.
A traffic shaper on port 8 can result in the overall utilization of egress bandwidth
for any one port being less the line rate because the packets being replicated
might not be transmitted to every port. Packets destined to some of the ports
contribute to the traffic shaping for all of the ports on the I/O module or IOA.

Configuring Hardware Multicast Packet Replication

To configure hardware multicast packet replication:
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Configuring Hardware Multicast Packet Replication