Cos-queue mapping – Comtrol ES8508 Series User Guide User Manual
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RocketLinx ES8508 Series User Guide: 2000575 Rev. A
CoS-Queue Mapping - 101
Configuration Using the Web Interface
CoS-Queue Mapping
Use this page to change the CoS values into the Physical Queue mapping table. Since the switch fabric of
ES8508 supports four queues, Lowest, Low, Middle, and High users should therefore assign how to map the
CoS value to the level of the physical queue.
You can assign the mapping table or follow the suggestion of the IEEE 802.1p standard. The ES8508 uses
IEEE 802.1p suggestion as default values. CoS Values 1 and 2 are mapped to physical Queue 0, the lowest
queue. CoS Values 0 and 3 are mapped to physical Queue 1, the low/normal physical queue. CoS Values 4 and
5 are mapped to physical Queue 2, the middle physical queue. CoS Values 6 and 7 are mapped to physical
Queue 3, the high physical queue.
Class of service (CoS) is a 3 bit field within a layer two Ethernet frame header defined by IEEE 802.1p when
using IEEE 802.1Q tagging. The field specifies a priority value of between 0 and 7 inclusive that can be used
by Quality of Service (QoS) disciplines to differentiate traffic.
While CoS operates only on Ethernet at the data link layer, other QoS mechanisms (such as DiffServ) operate
at the network layer and higher. Others operate on other physical layers. Although IEEE 802.1Q tagging
must be enabled to communicate priority information from switch to switch, some switches use CoS to
internally classify traffic for QoS purposes.
Differentiated Services (DiffServ) is a model where traffic is treated by intermediate systems with relative
priorities based on the type of services (ToS) field. Defined in RFC2474 and RFC2475, the DiffServ standard
supersedes the original specification for defining packet priority described in RFC791. DiffServ increases the
number of definable priority levels by reallocating bits of an IP packet for priority marking. The DiffServ
architecture defines the DiffServ field, which supersedes the ToS field in IPv4 to make per-hop behavior
(PHB) decisions about packet classification and traffic conditioning functions, such as; metering, marking,
shaping, and policing.
After configuration, press Apply to enable the settings.
Note: You must Save the settings (
), if you want to maintain these settings if the ES8508 is powered
off.
Trust Mode
Trust Mode indicates the Queue Mapping types that you can select.
•
COS Only (default): The port priority follows the CoS-Queue Mapping you have
assigned. The ES8508 provides the default CoS-Queue table for which you can refer
to for the next command.
•
DSCP Only: Port priority only follows the DSCP-Queue Mapping you have assigned.
•
COS first: Port priority follows the CoS-Queue Mapping first, and then the DSCP-
Queue Mapping rule.
•
DSCP first: Port priority follows the DSCP-Queue Mapping first, and then the CoS-
Queue Mapping rule.
Apply
Click Apply to apply the settings.
Note: You must Save the settings (
), if you want to maintain these settings if the
ES8508 is powered off.
QoS Setting Page (Continued)