
Industrial Managed
Ethernet Switch
User Manual
錯誤
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Page
51
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191
Figure 2.55 depicts the QoS Setting webpage
.
By default, the
QoS Mode
in the managed switch works under the
Strict Priority packet scheduling mode. For Deficit Weighted Round Robin (DWRR), packet weights of Q0 to Q3 are
set in term of packet as followings.
-
COS Q0 = 2 packets
-
COS Q1 = 1 packet
-
COS Q2 = 4 packets
-
COS Q3 = 8 packets
Note that Q4 to Q7 are working in strict priority queue scheduling only.
Figure 2.55 QoS Setting Webpage
On the second option of the QoS Setting webpage in Figure 2.55, the users can select the
QoS Type
or the packet
classification scheme that will be used by the managed switch. There are two classification types to choose from
the drop-down list:
802
.
1p CoS only
or
Both 802
.
1p CoS and DiffServ
. For
802
.
1p CoS only
, switch only checks
Layer 2 (L2) 802
.
1p CoS priority bits, whilefor
DiffServ
, switch checks DiffServ Code Point (DSCP) for header
mapping. The default classification type is
802
.
1p CoS only
. Note that after changing the schedule discipline (
QoS
Mode
) and/or selecting the classification type (
QoS Type
), please click on the
Update
button to enable them on
the switch.
2.4.1.2
CoS Queue Mapping
802
.
1p CoS is the QoS technique developed by the IEEE P802
.
1p working group, known as Class of Service (CoS)
mechanism at Media Access Control (MAC) level. It is a 3-bit field called the priority code point (PCP) within an
Ethernet frame header (Layer 2) when using VLAN tagged frames as defined by IEEE 802
.
1Q. It specifies a priority
value between 0 and 7 that can be used by QoS to differentiate traffic. When this option is enabled, the switch
inspects the 802
.
1p CoS tag in the MAC frame to determine the priority of each frame.