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

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Guidelines for Managing Buffers on page 20
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RED and WRED Overview on page 26
Memory Requirements for Queue and Buffers
JUNOSe software uses 128-byte buffers.
The egress memory available for queues available depends on the ASIC and the line
module. Table 5 on page 19 lists the egress memory.
Table 5: Egress Memory and Region Size on ASIC Line Modules
Region Size (MB)
Egress Memory
(MB)
Line Module ASIC
4 32 All EFA line modules EFA
8 64 GE-2 and GE-HDE FFA
16 128 OC48
16 128 ES2 4G LM
12 96 ES2 10G LM TFA
Related Topics
To identify the type of ASIC used by a line module, see the ERX Module Guide
and the E120 and E320 Module Guide
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Guidelines for Managing Queue Thresholds on page 19
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Guidelines for Managing Buffers on page 20
Guidelines for Managing Queue Thresholds
To prevent the router from setting queue thresholds too low or too high, you can
specify minimum and maximum queue thresholds. You can also specify the
conformed length and exceeded length as percentages of the committed length.
Guidelines for Configuring a Maximum Threshold
We recommend that you constrain queue thresholds using committed or conformed
threshold settings; any unused memory is redistributed to queues whose thresholds
are not constrained. This use of thresholds is analogous to the way that shaping rates
constrain bandwidth and cause bandwidth redistribution to unconstrained queues.
For example, voice queues are scheduled at strict priority; therefore, they require
very little buffering. Configuring a maximum queue threshold enables the system to
allocate more buffers to other queues in the system. Video queues are similar but
Memory Requirements for Queue and Buffers
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Chapter 3: Configuring Queue Profiles for Buffer Management