Juniper JUNOS 10.1 - CONFIGURATION GUIDE 1-2010 Configuration Manual page 389

a weighted round robin (WRR) algorithm. One queue is serviced with strictly high
priority and the remaining queues are serviced with the WRR.
For Layer 2 circuit trunk mode, only strict mode is supported. Alternate mode is not
supported.
To configure CoS queues in Layer 2 circuit trunk mode, perform the following tasks:
Include the
1. encapsulation atm-ccc-cell-relay
at-fpc/pic/port] hierarchy level:
[edit interfaces at-fpc/pic/port]
encapsulation atm-ccc-cell-relay;
Include the
2. scheduler-maps
hierarchy level:
atm-options]
[edit interfaces at-fpc/pic/port atm-options]
scheduler-maps map-name {
forwarding-class (class-name | assured-forwarding | best-effort |
expedited-forwarding | network-control);
vc-cos-mode strict;
}
3. Include the atm-scheduler-map
[edit interfaces at-fpc/pic/port unit logical-unit-number]
[edit interfaces at-fpc/pic/port unit logical-unit-number]
atm-scheduler-map (map-name | default);
trunk-bandwidth rate;
trunk-id number;
For information about ATM scheduler maps, see "Configuring an ATM Scheduler
Map" on page 349.
For information about trunk identification numbers, see "Configuring Layer 2 Circuit
Transport Mode" on page 308. For information about trunk bandwidths, see
"Configuring Layer 2 Circuit Trunk Mode Scheduling" on page 317.
Strict mode CoS queue priority works as follows:
Scheduling—One queue has strictly high priority and is always serviced before
the remaining queues are serviced by a weighted round robin. This means the
packets in a priority queue are sent first until the queue is empty. Then
high
priority queues send packets until their weight quota becomes zero or negative.
Latency—Each trunk is associated with a trunk bandwidth. The trunk bandwidth
is the maximum bandwidth used each time a trunk is serviced. In the scheduling
process, each trunk is serviced in a WRR. The maximum latency for any trunk
to begin transmitting is equal to the sum of the weights of all previously queued
trunks. Trunks without data do not affect output scheduling. As long as all the
trunks have data, the exact weight proportions are maintained. If a trunk runs
out of data during its turn, it is no longer included in the WRR. When the trunk
gets more data, the trunk is placed at the end of the queue. For more information,
see "Configuring Layer 2 Circuit Trunk Mode Scheduling" on page 317.
Chapter 13: Configuring ATM Interfaces
statement at the
statement at the
[edit interfaces at-fpc/pic/port
, trunk-bandwidth , and
Configuring CoS Queues in Layer 2 Circuit Trunk Mode
[edit interfaces
trunk-id statements at the
hierarchy level:
low
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