R3166-R3206-HP High-End Firewalls Network Management Configuration Guide-6PW101

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was introduced to combine PQ and CBQ to transmit delay sensitive flows like voice packets
preferentially.
When defining traffic classes for LLQ, you can configure a class of packets to be transmitted preferentially.
Such a class is called a priority class. The packets of all priority classes are assigned to the same priority
queue. It is necessary to check bandwidth restriction of each class of packets before the packets are
enqueued. During the dequeuing operation, packets in the priority queue are transmitted first. WFQ is
used to dequeue packets in the other queues.
In order to reduce the delay of the other queues except the priority queue, LLQ assigns the maximum
available bandwidth for each priority class. The bandwidth value is used to police traffic in the case of
congestion. In the case of no congestion, a priority class can use more than the bandwidth assigned to
it. In the case of congestion, the packets of each priority class exceeding the assigned bandwidth are
discarded. LLQ can also specify burst-size.
The system matches packets with match criteria in the following order:
• Match packets with priority classes and then the other classes.
• Match packets with priority classes in the order configured.
• Match packets with other classes in the order configured.
• Match packets with match criteria in a class in the order configured.
QoS policy overview
In policy approach, you configure QoS service parameters by using QoS policies. A QoS policy defines
the shaping, policing, or other QoS actions to take on different classes of traffic. It is a set of
class-behavior associations.
A class is a set of match criteria for identifying traffic, and it uses the AND or OR operator:
• If the operator is AND, a packet must match all the criteria to match the class.
• If the operator is OR, a packet matches the class if it matches any of the criteria in the class.
A traffic behavior defines a set of QoS actions to take on packets, such as priority marking and redirect.
By associating a traffic behavior with a class in a QoS policy, you apply the specific set of QoS actions
to the class of traffic.
You can apply the QoS policy to a port to regulate the incoming/outgoing traffic of the port. A QoS
policy can be applied to multiple ports. Only one QoS policy can be applied in one direction (inbound
or outbound) of a port.
Traffic policing
If user traffic is not limited, burst traffic can make the network congested. Therefore it is necessary to limit
user traffic in order to better utilize network resources and provide better services for users. For example,
you can configure a flow to use only the resources committed to it in a time range, thus avoiding network
congestion caused by burst traffic.
Traffic policing limits traffic rate and resource usage according to traffic specifications. It polices
particular flows entering a device according to configured specifications and is usually applied in the
inbound direction of a port. When a flow exceeds the specification, some restriction or punishment
measures can be taken to prevent overconsumption of network resources and protect the commercial
benefits of the carrier. The prerequisite for traffic policing is to know whether a traffic flow has exceeded
the specifications. If yes, proper traffic control policies apply. Generally, token buckets are used to
evaluate traffic specifications.