Brocade 6910 Ethernet Access Switch Configuration Guide (Supporting R2.2.0.0) User Manual
Page 889
Brocade 6910 Ethernet Access Switch Configuration Guide
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Creating QoS Policies
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The behavior of the meter is specified in terms of its mode and two token buckets, P and C,
which are based on the rates PIR and CIR, respectively. The maximum size of the token bucket
P is BP and the maximum size of the token bucket C is BC.
The token buckets P and C are initially (at time 0) full, that is, the token count Tp(0) = BP and
the token count Tc(0) = BC. Thereafter, the token count Tp is incremented by one PIR times per
second up to BP and the token count Tc is incremented by one CIR times per second up to BC.
When a packet of size B bytes arrives at time t, the following happens if trTCM is configured to
operate in Color-Blind mode:
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If Tp(t)-B < 0, the packet is red, else
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if Tc(t)-B < 0, the packet is yellow and Tp is decremented by B, else
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the packet is green and both Tp and Tc are decremented by B.
When a packet of size B bytes arrives at time t, the following happens if trTCM is configured to
operate in Color-Aware mode:
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If the packet has been precolored as red or if Tp(t)-B < 0, the packet is red, else
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if the packet has been precolored as yellow or if Tc(t)-B < 0, the packet is yellow and Tp is
decremented by B, else
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the packet is green and both Tp and Tc are decremented by B.
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The trTCM can be used to mark a IP packet stream in a service, where different, decreasing
levels of assurances (either absolute or relative) are given to packets which are green, yellow,
or red. Refer to RFC 2698 for more information on other aspects of trTCM.
Random Early Detection – RED starts dropping yellow and red packets when the buffer fills up to
0x60 packets, and then starts dropping any packets regardless of color when the buffer fills up to
0x80 packets.
CLI References
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Command Usage
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A policy map can contain 1024 class statements that can be applied to the same interface
(see
“Attaching a Policy Map to a Port”
on page 839). Up to 32 policy maps can be configured
for ingress ports.
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After using the policy map to define packet classification, service tagging, and bandwidth
policing, it must be assigned to a specific interface by a service policy (see
on page 839) to take effect.
Parameters
These parameters are displayed:
Add
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Policy Name – Name of policy map. (Range: 1-32 characters)
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Description – A brief description of a policy map. (Range: 1-256 characters)
Add Rule
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Policy Name – Name of policy map.
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Class Name – Name of a class map that defines a traffic classification upon which a policy can
act.