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JunosE 11.3.x Multicast Routing Configuration Guide
Configuring Hardware Multicast Packet Replication
22
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.
To configure hardware multicast packet replication:
Configure port 8 on a high-density Ethernet module to accept redirected egress
1.
multicast traffic.
a. Specify the Gigabit Ethernet interface on port 8.
b. Create a VLAN major interface.
Copyright © 2010, Juniper Networks, Inc.
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