Juniper JUNOSE 11.1.X - QUALITY OF SERVICE CONFIGURATION GUIDE 3-21-2010, Configuration Manual

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Committed drop threshold—Threshold above which committed drop rate events
are counted.
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Conformed drop threshold—Threshold above which conformed drop rate events
are counted.
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Exceeded drop threshold—Threshold above which exceeded drop rate events
are counted.
Rate Statistics
You can configure the E Series router to gather statistics for the rate at which queues
forward and drop packets.
Queue rate statistics measure the forwarding and drop rates of each queue in bits
per second. All bytes in the Layer 2 encapsulation are included in the rate calculation.
For example, rates for a queue on Ethernet include the Ethernet and VLAN
encapsulations.
For ATM modules, you can optionally configure queue statistics and queue rates to
include the cell encapsulation and padding. Cell encapsulation and padding are
referred to as the
cell tax . The QoS shaping mode that you set on ATM line modules
determines whether queue rate statistics include cell tax.
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If the interface is configured with frame-based QoS shaping mode, the egress
queue measures frame rate statistics; an ATM cell tax is not included.
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If the interface is configured with cell-based QoS shaping mode, the egress queue
measures cell rate statistics; cell rates include ATM Adaptation Layer 5 (AAL5)
encapsulation and cell padding.
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If the interface is configured with byte adjustment, the egress queue measures
rate statistics that are adjusted to the byte adjustment value.
NOTE: If you change the QoS shaping mode value in the middle of a rate period, the
gathered rates are a mixture of cell- and frame-based rates for that one rate period.
The next rate period uses a rate based on the new QoS shaping mode setting.
Event Statistics
You can configure the E Series router to count the number of times that forwarding
or drop rates exceed a specific threshold. Events can be useful when you are
monitoring service level agreements. For example, you might count the number of
times that the drop rate of a queue is nonzero.
Bulk Statistics Support for QoS Statistics
You can obtain queue-level QoS statistics for each logical interface by querying the
SNMP MIB. However, using SNMP to obtain queue-level statistics consumes significant
network bandwidth because SNMP polls large volumes of data frequently. As an
alternative to using the SNMP MIB, you can use the bulkstats statistics application.
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QoS Statistics Overview
JUNOSe 11.1.x Quality of Service Configuration Guide