ZyXEL Communications FMG Series User Manual page 27

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 FMG uses the Token Bucket
algorithm to allow a certain amount of large bursts while keeping a limit at the average rate.
Traffic Rate
Time
(Before Traffic Shaping)
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.
Traffic Rate
Time
(Before Traffic Policing)
The FMG supports three incoming traffic metering algorithms: Token Bucket Filter (TBF), Single Rate Two
Color Maker (srTCM), and Two Rate Two Color Marker (trTCM). You can specify actions which are
performed on the colored packets. See
algorithm.
Chapter 5 Advance
Section 5.5 on page 31
FMG Series User's Guide
27
Traffic Rate
Time
(After Traffic Shaping)
Traffic Rate
Time
(After Traffic Policing)
for more information on each metering