Forwarding Classes - Alcatel-Lucent 7450 Quality Of Service Manual

QoS Overview
In the Alcatel-Lucent service router's service model, a service is provisioned on the provider-
edge (PE) equipment. Service data is encapsulated and then sent in a service tunnel to the far-
end Alcatel-Lucent service router where the service data is delivered.
The operational theory of a service tunnel is that the encapsulation of the data between the
two Alcatel Lucent service routers (such as the 7950 XRS, 7750 SR, 7750 SR MG and
7450 ESS) appear like a Layer 2 path to the service data although it is really traversing an IP
or IP/MPLS core. The tunnel from one edge device to the other edge device is provisioned
with an encapsulation and the services are mapped to the tunnel that most appropriately
supports the service needs.
The router supports eight forwarding classes internally named: Network-Control, High-1,
Expedited, High-2, Low-1, Assured, Low-2 and Best-Effort. The forwarding classes are
discussed in more detail in
Router QoS policies control how QoS is handled at distinct points in the service delivery
model within the device. There are different types of QoS policies that cater to the different
QoS needs at each point in the service delivery model. QoS policies are defined in a global
context in the router and only take effect when the policy is applied to a relevant entity.
QoS policies are uniquely identified with a policy ID number or name. Policy ID 1 or Policy
ID "default" is reserved for the default policy which is used if no policy is explicitly applied.
The QoS policies within the router can be divided into three main types:

Forwarding Classes

Routers support multiple forwarding classes and class-based queuing, so the concept of
forwarding classes is common to all of the QoS policies.
Each forwarding class (also called Class of Service (CoS)) is important only in relation to the
other forwarding classes. A forwarding class provides network elements a method to weigh
the relative importance of one packet over another in a different forwarding class.
Queues are created for a specific forwarding class to determine the manner in which the queue
output is scheduled into the switch fabric. The forwarding class of the packet, along with the
profile state, determines how the packet is queued and handled (the per hop behavior (PHB))
at each hop along its path to a destination egress point. Routers support eight (8) forwarding
classes
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• QoS policies are used for classification, defining and queuing attributes and marking.
• Slope policies define default buffer allocations and WRED slope definitions.
• Scheduler policies determine how queues are scheduled.
(Table 2).
Forwarding Classes.
Quality of Service Guide