ZyXEL Communications P-870HW-51A V2, Руководство пользователя

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Chapter 11 Quality of Service (QoS)
P-870HW-51a v2 User’s Guide
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11.2 What You Need to Know
The following terms and concepts may help as you read through this chapter.
QoS versus Cos
QoS is used to prioritize source-to-destination traffic flows. All packets in the same flow are
given the same priority. CoS (class of service) is a way of managing traffic in a network by
grouping similar types of traffic together and treating each type as a class. You can use CoS to
give different priorities to different packet types.
CoS technologies include IEEE 802.1p layer 2 tagging and DiffServ (Differentiated Services
or DS). IEEE 802.1p tagging makes use of three bits in the packet header, while DiffServ is a
new protocol and defines a new DS field, which replaces the eight-bit ToS (Type of Service)
field in the IP header.
Tagging and Marking
In a QoS class, you can configure whether to add or change the DSCP (DiffServ Code Point)
value, IEEE 802.1p priority level and VLAN ID number in a matched packet. When the packet
passes through a compatible network, the networking device, such as a backbone switch, can
provide specific treatment or service based on the tag or marker.
11.3 The Quality of Service Screen
Click Advanced Setup > Quality of Service to open the screen as shown next.
Use this screen to enable or disable QoS and set the default DSCP value for incoming traffic
does not match a class. See
Section 11.1 on page 117 for more information.
Figure 62 QoS
The following table describes the labels in this screen.
Table 37 QoS
LABEL DESCRIPTION
Active QoS Select the check box to turn on QoS to improve your network performance.
Select Default
DSCP Mark This field is available only when you select Enable QoS .
If you enable QoS and incoming traffic does not match a class configured in the
Class Setup screen, the ZyXEL Device sets the DSCP field in the packets with the
value you select here. If you select No Change , the ZyXEL Device keeps the
DSCP fields in the packets.