Cisco 500 Series Administration Guide

Quality of Service
QoS Features and Components
Cisco 500 Series Stackable Managed Switch Administration Guide 600
28
QoS Modes
The QoS mode that is selected applies to all interfaces in the system.
• Basic Mode—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 Global Settings page. For
every value of that field, an egress queue is assigned where the frame is
sent in the CoS/802.1p to Queue page or the DSCP to Queue 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.

Cisco 500 Series Specifications

General

Model	Cisco 500 Series
Category	Switch
Mounting	Rack-mountable
Management	Web-based, CLI, SNMP
Ports	24, 48
Port Speed	10/100/1000 Mbps
PoE Support	Available on some models
Switching Capacity	Up to 176 Gbps
MAC Address Table Size	16, 000 entries
Security	ACLs, 802.1X
Quality of Service (QoS)	Yes
Dimensions	Varies by model
Weight	Varies by model
Humidity	10% to 90% non-condensing
Power Supply	Internal
Power Consumption	Varies by model
Jumbo Frame Support	Up to 9216 bytes