Brocade Communications Systems Brocate Ethernet Access Switch 6910 User Manual
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Brocade 6910 Ethernet Access Switch Configuration Guide
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Creating QoS Policies
39
When a packet of size B bytes arrives at time t, the following happens if trTCM is configured to
operate in Color-Blind mode:
•
If Tp(t)-B < 0, the packet is red, else
•
if Tc(t)-B < 0, the packet is yellow and Tp is decremented by B, else
•
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:
•
If the packet has been precolored as red or if Tp(t)-B < 0, the packet is red, else
•
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
•
the packet is green and both Tp and Tc are decremented by B.
•
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
•
Command Usage
•
A policy map can contain 1024 class statements that can be applied to the same interface
(
). Up to 32 policy maps can be configured for ingress ports.
•
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 (
) to take
effect.
Parameters
These parameters are displayed:
Add
•
Policy Name – Name of policy map. (Range: 1-32 characters)
•
Description – A brief description of a policy map. (Range: 1-256 characters)
Add Rule
•
Policy Name – Name of policy map.
•
Class Name – Name of a class map that defines a traffic classification upon which a policy can
act.
•
Action – This attribute is used to set an internal QoS value in hardware for matching packets.
The PHB label is composed of five bits, three bits for per-hop behavior, and two bits for the
color scheme used to control queue congestion with the srTCM and trTCM metering functions.
•
Set CoS – Configures the service provided to ingress traffic by setting an internal CoS
value for a matching packet (as specified in rule settings for a class map). (Range: 0-7)
See
Table 164, "Default Mapping of CoS/CFI to Internal PHB/Drop Precedence," on
).