7950 XRS Quality of Service Guide
Page 181
forwarding class is not explicitly defined in the rule, the forwarding class is inherited based on previous
rule matches.
Default
None
priority {in|out|use-de} —
All frames that are assigned to this forwarding class will be considered in or out
of profile based on this command or to use the default. In case of congestion, the in- profile frames are
preferentially queued over the out-of-profile frames
Values
in
— All frames are treated as in-profile.
out
—
All frames are treated as out of profile.
use-de
— T
he profile of all frames is set according to the DEI bit.
dscp
Syntax
dscp
dscp-name
[
dscp-name...
(
upto 8 max
)]
fc
fc-name
[
priority
{
low
|
high
}]
no dscp
dscp-name
[
dscp-name...
(
upto 8 max
)]
Context
config>qos>sap-ingress
Description
This command explicitly sets the forwarding class or subclass or enqueuing priority when a packet is
marked with the DiffServ Code Point (DSCP) value contained in the
dscp-name
. A list of up to 8 dscp-
names can be entered on a single command. The lists of dscp-names within the configuration are managed
by the system to ensure that each list does not exceed 8 names. Entering more than 8 dscp-names with the
same parameters (
fc
,
priority
) will result in multiple lists being created. Conversely, multiple lists with the
same parameters (fc, priority) are merged and the lists repacked to a maximum of 8 per list if dscp-names are
removed or the parameters changed so the multiple lists use the same parameters. Also, if a subset of a list is
entered with different parameters then a new list will be created for the subset. Note that when the list is
stored in the configuration, the dscp-names are sorted by their DSCP value in ascending numerical order,
consequently the order in the configuration may not be exactly what the user entered.
Adding a DSCP rule on the policy forces packets that match the DSCP value specified to override the
forwarding class and enqueuing priority based on the parameters included in the DSCP 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 DSCP value (referred to here by
dscp-name
) is derived from the most significant six bits in the IPv4
header ToS byte field (DSCP bits) or the Traffic Class field from the IPv6 header. If the packet does not have
an IP header, dscp based matching is not performed. The six DSCP bits define 64 DSCP values used to map
packets to per-hop Quality-of-Service (QoS) behavior. The most significant three bits in the IP header ToS
byte field are also commonly used in a more traditional manner to specify an IP precedence value, causing
an overlap between the precedence space and the DSCP space. 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 specified the
dscp-names
from the explicit DSCP classification
rule in the SAP ingress policy. As
dscp-names
are removed, the system repacks the lists of dscp-names with
Summary of Contents for 7950
Page 12: ...Page 12 7950 XRS Quality of Service Guide List of Figures ...
Page 16: ...Preface Page 16 7950 XRS Quality of Service Guide ...
Page 82: ...Editing QoS Policies Page 82 7950 XRS Quality of Service Guide ...
Page 90: ...Applying Network Queue Policies Page 90 7950 XRS Quality of Service Guide ...
Page 96: ...Editing QoS Policies Page 96 7950 XRS Quality of Service Guide ...
Page 98: ...Command Hierarchies Page 98 7950 XRS Quality of Service Guide ...
Page 108: ...Command Hierarchies Page 108 7950 XRS Quality of Service Guide ...
Page 156: ...Basic Configurations Page 156 7950 XRS Quality of Service Guide exit exit ...
Page 164: ...Queue Depth Monitoring Page 164 7950 XRS Quality of Service Guide ...
Page 304: ...Service Queue QoS Policy Commands Page 304 7950 XRS Quality of Service Guide ...
Page 368: ...Command Hierarchies Page 368 7950 XRS Quality of Service Guide ...
Page 430: ...Configuration Commands Page 430 7950 XRS Quality of Service Guide ...
Page 532: ...Editing QoS Policies Page 532 7950 XRS Quality of Service Guide ...
Page 552: ...Editing Advanced Policies Page 552 7950 XRS Quality of Service Guide ...
Page 600: ...Command Hierarchies Page 600 7950 XRS Quality of Service Guide ...
Page 602: ...QoS Commands Page 602 7950 XRS Quality of Service Guide ...
Page 610: ...Standards and Protocols Page 610 7950 XRS Quality of Service Guide ...
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