Quality of Service
QoS Features and Components
Cisco Sx350, SG350X, SG350XG, Sx550X & SG550XG Series Managed Switches, Firmware Release 2.2.5.x
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QoS Modes
The QoS mode that is selected applies to all interfaces in the system.
•
Basic Mod
e—Class of Service (CoS).
All traffic of the same class receives the same treatment, which is the single QoS action
of determining the egress queue on the egress port, based on the indicated QoS value in
the incoming frame. This can be the VLAN Priority Tag (VPT) 802.1p value in Layer
2 and the Differentiated Service Code Point (DSCP) value for IPv4 or Traffic Class
(TC) value for IPv6 in
Layer 3. When operating in Basic Mode, the device trusts this external assigned QoS
value. The external assigned QoS value of a packet determines its traffic class and
QoS.
The header field to be trusted is entered in the
page. For every value of
that field, an egress queue is assigned where the frame is sent in the
or the
page (depending on whether the trust mode is CoS/
802.1p or DSCP, respectively).
•
Advanced Mode
—Per-flow Quality of Service (QoS).
In advanced mode, a per flow QoS consists of a class map and/or a policer:
-
A class map defines the kind of traffic in a flow, and contains one or more ACLs.
Packets that match the ACLs belong to the flow.
-
A policer applies the configured QoS to a flow. The QoS configuration of a flow
may consist of egress queue, the DSCP or CoS/802.1p value, and actions on out of
profile (excess) traffic.
•
Disable Mode
—In this mode all traffic is mapped to a single best effort queue, so that
no type of traffic is prioritized over another.
Only a single mode can be active at a time. When the system is configured to work in QoS
Advanced mode, settings for QoS Basic mode are not active and vice versa.
When the mode is changed, the following occurs:
•
When changing from QoS Advanced mode to any other mode, policy profile
definitions and class maps are deleted. ACLs bonded directly to interfaces remain
bonded.
•
When changing from QoS Basic mode to Advanced mode, the QoS Trust mode
configuration in Basic mode is not retained.
•
When disabling QoS, the shaper and queue setting (WRR/SP bandwidth setting) are
reset to default values.
