Precedence Levels; Precedence Levels For Static Pvcs - Juniper JUNOSE 11.1.X - LINK LAYER CONFIGURATION 4-7-2010 Configuration Manual

JUNOSe 11.1.x Link Layer Configuration Guide

Precedence Levels

Precedence levels play an important role in determining how the router assigns the
attribute values for statically created and dynamically created PVCs that have
associated VC classes.

Precedence Levels for Static PVCs

For PVCs that are statically created, the router determines the PVC attribute values
according to the following precedence levels, in order from highest precedence to
lowest precedence:
1.
2.
3.
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Configuring ATM VC Classes
In a typical scenario, you might group subscribers based on their OAM and traffic
requirements, and then create a VC class for each subscriber group. For example,
you might create two VC classes: premium-subscriber-class and
economy-subscriber-class.
In premium-subscriber-class, you might enable F5 OAM VC integrity (with the
oam-pvc manage command), and configure a traffic class that has a higher
scheduling priority, such as CBR (with the cbr command). Conversely, in
economy-subscriber-class, you might retain the default setting that disables F5
OAM VC integrity, and configure a traffic class that has a lower scheduling priority,
such as UBR with or without a PCR (with the ubr command). By assigning each
VC class to the appropriate interfaces or individual circuits, you can group and
manage the PVCs associated with the VC class based on the network requirements
of the subscribers they serve.
VC classes facilitate modifications to PVC attributes.
If the OAM or traffic requirements change for a particular subscriber group, you
can simply reconfigure the VC class associated with the PVCs for that subscriber
group. This method is easier and less time-consuming than having to modify the
attributes for a large number of PVCs by using individual CLI commands.
Modifications to the attributes in a VC class affect PVCs that are already associated
with this VC class as well as PVCs subsequently created for this class.
The most recent explicitly set value for a PVC attribute always has the highest
precedence and overrides any settings in the VC class. Explicitly set values for
PVC attributes are those values configured with the CLI (by using the atm pvc
command or commands in ATM VC Configuration mode), SNMP, or assigned
by RADIUS.
If an attribute value is not explicitly specified, the router takes the value for that
attribute from the assigned VC class, in the following order of precedence:
a. Attribute value specified in the VC class assigned to this PVC
b. Attribute value specified in the VC class assigned to the ATM 1483
subinterface on which this PVC is created
c. Attribute value specified in the VC class assigned to the ATM major interface
on which this PVC is created
If no PVC attributes are explicitly specified and no VC class assignments exist,
the router applies the default values for the commands listed in Table 8 on