Alcatel-Lucent 7450 Manual page 680

Page 680
Each time the user executes the above command, with the same or different prefix policy
associations, or the user changes a prefix policy associated with a targeted peer template, the system
re-evaluates the prefix policy. The outcome of the re-evaluation will tell LDP if an existing targeted
Hello adjacency needs to be torn down or if an existing targeted Hello adjacency needs to have its
parameters updated on the fly.
If a /32 prefix is added to (removed from) or if a prefix range is expanded (shrunk) in a prefix list
associated with a targeted peer template, the same prefix policy re-evaluation described above is
performed.
The template comes up in the no shutdown state and as such it takes effect immediately. Once a
template is in use, the user can change any of the parameters on the fly without shutting down the
template. In this case, all targeted Hello adjacencies are updated.
The SR OS supports multiple ways of establishing a targeted Hello adjacency to a peer LSR:
• User configuration of the peer with the targeted session parameters inherited from
the config>router>ldp>targeted-session in the top level context or explicitly
configured for this peer in the config>router>ldp>targeted-session>peer context
and which overrides the top level parameters shared by all targeted peers. Let us
refer to the top level configuration context as the global context. Note that some
parameters only exist in the global context and as such their value will always be
inherited by all targeted peers regardless of which event triggered it.
• User configuration of an SDP of any type to a peer with the signaling tldp option
enabled (default configuration). In this case the targeted session parameter values
are taken from the global context.
• User configuration of a (FEC 129) PW template binding in a BGP-VPLS service. In
this case the targeted session parameter values are taken from the global context.
• User configuration of a (FEC 129 type II) PW template binding in a VLL service
(dynamic multi-segment PW). In this case the target session parameter values are
taken from the global context
• User configuration of a mapping of a targeted session peer parameter template to a
prefix policy when the peer address exists in the TE database (this feature). In this
case, the targeted session parameter values are taken from the template.
Since the above triggering events can occur simultaneously or in any arbitrary order, the LDP code
implements a priority handling mechanism in order to decide which event overrides the active
targeted session parameters. The overriding trigger will become the owner of the targeted adjacency
to a given peer. The following is the priority order:
• Priority 1: manual configuration of session parameters
• Priority 2: mapping of targeted session template to prefix policy.
• Priority 3: manual configuration of SDP, PW template binding in BGP-AD VPLS
and in FEC 129 VLL.
Note that any parameter value change to an active targeted Hello adjacency caused by any of the
above triggering events is performed on the fly by having LDP immediately send a Hello message
with the new parameters to the peer without waiting for the next scheduled time for the Hello
7450 ESS MPLS Guide