ZyXEL Communications P-3202HN-Ba User Manual page 164

Chapter 14 Quality of Service (QoS)
14.1.2 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.
14.2 The QoS General Screen
Click Advanced > QoS to open the screen as shown next.
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IAD User's Guide