Zyxel P-792H v2 [202/472] Qos versus cos

Zyxel P-792H v2 [202/472] Qos versus cos
Chapter 15 Quality of Service (QoS)
P-792H v2 User’s Guide
202
1 First, you have to configure WAN connection(s) in Network > WAN > Internet
Access Setup and Network > WAN > More Connections. Click the Advanced
Setup button on the corresponding PVC setting screens to configure ATM QoS, if
you want to prioritize traffic and eliminate congestion over the ATM network (at
the ATM layer).
2 Configure queue settings in Advanced > QoS > Queue Setup according to the
priority you want to apply to different types of traffic.
3 Configure class settings in Advanced > QoS > Class Setup. This associates
queues with PVCs by mapping the priority of queues to the index number of PVCs.
15.2.1 What You Can Do in the QoS Screens
•Use the General screen (Section 15.3 on page 207) to enable QoS on the P-
792H v2, decide allowable bandwidth using QoS and configure priority mapping
settings for traffic that does not match a custom class.
•Use the Class Setup screen (Section 15.4 on page 208) to set up classifiers to
sort traffic into different flows and assign priority and define actions to be
performed for a classified traffic flow.
•Use the Monitor screen (Section 15.5 on page 214) to view the P-792H v2’s
QoS-related packet statistics.
15.2.2 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.

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