ZyXEL Communications P-660HN-F1A, User Manual

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Chapter 16 Quality of Service (QoS)
P-660HN-F1A User’s Guide
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16.2.2 What You Need to Know About QoS
QoS versus Cos
QoS is used to prioritize source-to-destination traffic flows. All packets in the same
flow are given the same priority. Class of Service (CoS) 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 Differentiated Services
(DiffServ 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 Type of Service (ToS) field in the IP header.
Tagging and Marking
In a QoS class, you can configure whether to add or change the DiffServ Code
Point (DSCP) 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.
Finding Out More
See Section 16.10 on page 269 for advanced technical information on QoS.
16.2.3 QoS Class Setup Example
In the following figure, your Internet connection has an upstream transmission
speed of 50 Mbps. You configure a classifier to assign the highest priority queue
(6) to VoIP traffic from the LAN interface, so that voice traffic would not get
delayed when there is network congestion. Traffic from the boss’s IP address
(192.168.1.23 for example) is mapped to queue 5. Traffic that does not match