Alcatel-Lucent 7950 Quality Of Service Manual page 210

Service Ingress QoS Policy Commands
12.
When collect-stats is enabled, the counters are used by the system to generate the following statistics:
a.
b.
c.
d.
e.
f.
prec
Syntax prec ip-prec-value fc fc-name [priority {high | low}]
no prec ip-prec-value
Context config>qos>sap-ingress
Description
This command explicitly sets the forwarding class or enqueuing priority when a packet is marked with an IP
precedence value (ip-prec-value). Adding an IP precedence rule on the policy forces packets that match the
specified ip-prec-value to override the forwarding class and enqueuing priority based on the parameters
included in the IP precedence rule.
When the forwarding class is not specified in the rule, a matching packet preserves (or inherits) the existing
forwarding class derived from earlier matches in the classification hierarchy.
When the enqueuing priority is not specified in the rule, a matching packet preserves (or inherits) the
existing enqueuing priority derived from earlier matches in the classification hierarchy.
The ip-prec-value is derived from the most significant three bits in the IP header ToS byte field (precedence
bits). The three precedence bits define 8 Class-of-Service (CoS) values commonly used to map packets to
per-hop Quality-of-Service (QoS) behavior. The precedence bits are also part of the newer DiffServ Code
Point (DSCP) method of mapping packets to QoS behavior. The DSCP uses the most significant six bits in
the IP header ToS byte and so overlaps with the precedence bits. Both IP precedence and DSCP
classification rules are supported. DSCP rules have a higher match priority than IP precedence rules and
where a dscp-name DSCP value overlaps an ip-prec-value, the DSCP rule takes precedence.
The no form of the command removes the explicit IP precedence classification rule from the SAP ingress
policy. Removing the rule on the policy immediately removes the rule on all ingress SAPs using the policy.
Parameters
ip-prec-value — The ip-prec-value is a required parameter that specifies the unique IP header ToS byte
precedence bits value that will match the IP precedence rule. If the command is executed more than
once with the same ip-prec-value, the previous forwarding class and enqueuing priority is completely
overridden by the new parameters or defined to be inherited when a forwarding class or enqueuing
priority parameter is missing.
A maximum of eight IP precedence rules are allowed on a single policy.
Page 210
'forwarded-out-that-turned-yellow'
'offered-in'
'offered-out'
'discard-in'
'discard-out'
'forward-in'
'forward-out'
= Derived from 4 - 8
= 1 + 2
= 3 + 4
= 5 + 7
= 6 + 8
= 9 + 11
= 10 + 12
7950 XRS Quality of Service Guide