BGP Auto-Discovery for LDP VPLS
Page 292 7210 SAS M Services Guide
Manually Provisioned SDP
The carrier is required to manually provision the SDP if they create transport tunnels using RSVP-
TE. Operators have the option to choose a manually configured SDP, if they use LDP as the tunnel
signaling protocol. The functionality is the same regardless of the signaling protocol.
Creating a BGP-AD enabled VPLS service on an ingress node with the manually provisioned SDP
option causes the Tunnel Manager to search for an existing SDP that connects to the far-end PE.
The far-end IP information is gleaned from the BGP next hop information in the NLRI. If a single
SDP exists to that PE, it is used. If no SDP is established between the two endpoints, the service
remains down until a manually configured SDP becomes active.
When multiple SDPs exist between two endpoints, the tunnel manager selects the appropriate
SDP. The algorithm preferred SDPs with the best (lower) metric. Should there be multiple SDPs
with equal metrics, the operational state of the SDPs with the best metric is considered. If the
operational state is the same, the SDP with the higher sdp-id is used. If an SDP with a preferred
metric is found with an operational state that is not active, the tunnel manager flags it as ineligible
and restarts the algorithm.
Automatic Instantiation of Pseudowires (SDP Bindings)
The choice of manual or auto provisioned SDPs has limited impact on the amount of required
provisioning. Most of the savings are achieved through the automatic instantiation of the
pseudowire infrastructure (SDP bindings). This is achieved for every auto-discovered VSIs
through the use of the pseudowire template concept. Each VPLS service that uses BGP AD
contains the “pw-template-binding” option defining specific layer 2 VPN parameters. This
command references a “pw-template” which defines the pseudowire parameters. The same
“pwtemplate” may be referenced by multiple VPLS services. As a result, changes to these
pseudowire templates have to be treated with great care as they may impact many customers at
once.
The Alcatel-Lucent implementation provides for safe handling of pseudowire templates. Changes
to the pseudowire templates are not automatically propagated. Tools are provided to evaluate and
distribute the changes. The following command is used to distribute changes to a “pw-template” at
the service level to one or all services that use that template.
PERs-4# tools perform service id 300 eval-pw-template 1 allow-service-impact
If the service ID is omitted, then all services are updated. The type of change made to the
“pwtemplate” influences how the service is impacted.
1. Adding or removing a split-horizon-group will cause the router to destroy the original object
and recreate using the new value.
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