Juniper JUNOSE 11.1.X - QUALITY OF SERVICE CONFIGURATION GUIDE 3-21-2010, Руководство по настройке

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because they are higher bandwidth, they might require higher maximum committed
thresholds.
You might want to limit latency of your multicast traffic by bounding the queue length
using a maximum committed threshold. The following example configures the
multicast queues so that the committed threshold never exceeds 20 KB, even when
the egress memory is lightly loaded. The forfeited buffers are allocated to other
queues.
host1(config)# queue-profile multicast
host1(config-queue)# committed-length 0 20000
host1(config-queue)# exit
Be sure to include 0 in the syntax, or you will configure a minimum threshold.
Guidelines for Configuring a Minimum Threshold
Configuring a minimum threshold does not guarantee that a queue always obtains
the minimum buffer allocation. You can configure 1000 queues with a minimum of
1 MB each, but the buffer memory is 32 MB or 128 MB, not 1 GB. In this case, the
system moves into higher operating regions (global utilization) if all these queues
buffer traffic, until it reaches 90 percent utilization. At that point, the thresholds must
reduce to the reserved percentages, and the queue thresholds drop from a high
threshold to a very low one. Queues are not guaranteed to obtain any buffering, and
are buffered in the order in which they are received.
You can configure a minimum committed threshold by specifying a value such as
1000 with the
committed-length command:
host1(config)# queue-profile multicast
host1(config-queue)# committed-length 1000 20000
host1(config-queue)# exit
Related Topics
Memory Requirements for Queue and Buffers on page 19
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Configuring Queue Profiles to Manage Buffers and Thresholds on page 22
Guidelines for Managing Buffers
Queue profiles enable you to manage queue thresholds and buffers to manage the
following common problems:
■
Queues that back up and consume too many buffers
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Queues that cannot obtain buffers when they need them (called buffer starvation )
You can set the buffer weight to ensure that some sets of queues get higher thresholds
than others. Buffer weight is analogous to weight in a scheduler profile. It directs the
router to set the queue thresholds proportionately.
20 ■
Guidelines for Managing Buffers
JUNOSe 11.1.x Quality of Service Configuration Guide