PHB_Definition;
“This is the Per Hop Behaviour of
the Behaviour Aggregate selected by
the DSCP value. It is a complex data
structure and it may possibly be
represented as a separate object.”
FEC;
“The value of this attribute is given
by the mapping from the traffic class
to the forwarding behaviour given to
the packets of this class in the MPLS
domain.”
TrafficParameters;
“The traffic parameters specify the
properties of the traffic trunk in
terms of static and/or dynamic
(traffic shaping) bitrates. As such,
they reflect the resource
requirements of the traffic trunk.”
GenericPathSelectionAndMaintenance;
ExplicitlyRouted_LSPCreation;
“The value of this attribute
evaluates to “true” when ER
LSPs are required. When hop-
by-hop setup governed by the
underlying routing protocol is
required the value evaluates to
“false”.”
PathPreferenceRule;
“This attribute has the value
“Mandatory” when no other path
may be used and “Optional”
when alternative paths may be
used. Path preference rules may
be applied recursively upon a
hierarchy of paths to cater for
cases like rerouting when alarms
occur.”
ResourceClassAffinity;
“This attribute defines a
sequence of resource class/
affinity tuples where the affinity
is the “applicable/not applicable”
property for each resource class.
Related to resource reservation
during ER-LSP setup, this
construct may e.g. support
explicit inclusion/exclusion of
certain links.”
Adaptivity;
“The adaptivity attribute
specifies whether re-optimisation
of the path is permitted or not.”
LoadShare;
“The amount of the overall
traffic trunk carried by this
sub-stream”
Priority;
“The relative importance of the
traffic trunk in question.”
Preemption;
“The preemption attribute specifies
whether this traffic trunk can
preempt lower priority traffic or not
and whether this traffic trunk can be
preempted by higher priority traffic
or not.”
BasicResilienceDecision;
“The basic resilience decision
attribute determines whether the
traffic trunk is to be rerouted when
a failure occurs.”
ExtendedResilienceBehaviour;
“The extended resilience behaviour
attribute specifies additional
behaviour to take place during a
failure situation such as the choice
of alternate paths to be used, if any.”
Policing;
“The policing attribute specifies the
actions to be taken when non-
compliant traffic parameters are
provided by the traffic trunk, i.e.
should it be rate-limited, tagged
or forwarded without any action.”
};
};3 Modelling Methodology
The methodology chosen has been developed by
the group of experts dealing with network level
modelling within ITU, i.e. Question 18 of SG4.
An overview can be found in [ITUmeth].A generic functional architecture for transport
networks as documented in [G.805] has been
developed by SG13. This has been used in spe-
cialisations for SDH, ATM, WDM, Access Net-
works and (under development) connectionless
communication (like IP).The concepts described in [G.805] are essential
to the understanding of the modelling methodol-
ogy and they will be described in the following
sub-section.3.1 The Generic Network
Architecture
A suitable abstraction level for dealing with
topology management issues is the network level
as opposed to the network element level. ITU
has developed a generic network level transport
functional model in the Rec. G.85x series that
serves as a suitable starting point for a topology
management model.[G.805] provides a high level view of the net-
work functions based on a small set of architec-
tural entities (functional blocks) interconnected
via reference points. Two main network repre-
sentations may be provided on the basis of this
architecture: