ZyXEL Communications P8701T, Руководство пользователя

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Chapter 8 Quality of Service (QoS)
Basic Home Station VDSL2 P8701T User’s Guide
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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.
Traffic Shaping
Bursty traffic may cause network congestion. Traffic shaping regulates packets to be transmitted
with a pre-configured data transmission rate using buffers (or queues). Your VDSL Router uses the
Token Bucket algorithm to allow a certain amount of large bursts while keeping a limit at the
average rate.
Traffic Policing
Traffic policing is the limiting of the input or output transmission rate of a class of traffic on the
basis of user-defined criteria. Traffic policing methods measure traffic flows against user-defined
criteria and identify it as either conforming, exceeding or violating the criteria.
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