41-13
Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
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Chapter 41 Configuring QoS
Understanding How QoS Works
Figure 41-8 Receive Queue Drop Thresholds
Ethernet Ingress Port Classification Features with a Layer 3 Switching Engine
You can use the
untrusted
,
trust-ipprec
,
trust-dscp
, and
trust-cos
port keywords to classify traffic on
a per-port basis for a Layer 3 switching engine to mark.
The
trust-ipprec
and
trust-dscp
keywords are supported only with a Layer 3 switching engine and are
not supported on
1q4t
ports except Gigabit Ethernet. On
1q4t
ports (except Gigabit Ethernet), the
trust-cos
port keyword displays an error message, activates receive-queue drop thresholds, and—as
indicated by the error message—does not apply the
trust-cos
trust state to traffic. You must configure
the
trust-cos
ACL that matches the ingress traffic to apply the
trust-cos
trust state.
In addition to per-port classification, you can create ACEs that classify traffic on a per-packet basis (for
IP and IPX traffic, see the
“Named IP ACLs” section on page 41-38
and the
“Creating or Modifying
Named IPX ACLs” section on page 41-42
) or on a per-frame basis (for other traffic, see the
“Creating
or Modifying Named MAC ACLs” section on page 41-43
), regardless of the port configuration (see the
“Marking Rules” section on page 41-21
).
To mark traffic in response to per-port classification, the traffic must match an ACE that contains the
dscp
ACE keyword (see the
“Marking Rules” section on page 41-21
). In their default configuration, the
ACEs in the default ACLs contain the
dscp
ACE keyword.
Table 41-1
lists the per-port classifications
and the marking rules that they invoke.
CoS
0
an
d
1
CoS
2
an
d
3
Co
S
4
an
d
5
C
oS
6
a
nd
7
Traffic is dropped
Drop threshold 4: 100%
Drop threshold 3: 80%
Drop threshold 2: 60%
Drop threshold 1: 50%
Available for
traffic with any
CoS value
Reserved for
CoS 6 and 7
Reserved for
CoS 4 and higher
Reserved for
CoS 2 and higher
Receive queue
(Default values shown)
100% available for CoS 6 and 7
80% available for CoS 4 and 5
60% available for CoS 2 and 3
50% available for CoS 0 and 1
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