Pseudowire Redundancy At A Pseudowire Switching Node; Pseudowire Redundancy For A Vpls Service - Alcatel-Lucent 7750 SR OS Service Manual

Pseudowire Redundancy
against a remote SAP failure. When the target destination PE for the primary and secondary
pseudowires is the same, T-PE1 will normally not switch the VLL path onto the secondary
pseudowire upon receipt of a pseudowire status notification indicating the remote SAP is DOWN
since the status notification is sent over both the primary and secondary pseudowires. However,
the status notification on the primary pseudowire may arrive earlier than the one on the secondary
pseudowire due to the differential delay between the paths. This will cause T-PE1 to switch the
path of the VLL to the secondary standby pseudowire and remain there until the status notification
is cleared. At that point in time, the VLL path is switched back to the primary pseudowire due to
the revertive behavior operation. The path will not switch back to a secondary path when it
becomes up even if it has a higher precedence than the currently active secondary path.
This application can make use of all types of VLL supported on the 7x50, for example, Apipe,
Fpipe, Epipe, and Ipipe services. A SAP can be configured on SONET/SDH port which is part of
an APS group. However, if a SAP is configured on a MC-LAG instance, only the Epipe service
type will be allowed.

Pseudowire Redundancy at a Pseudowire Switching Node

It is possible to provide additional VLL resilience by configuring pseudowire redundancy at the S-
PE nodes. This means that a redundant pseudowire pair is configured on both the left and right
sides of the VLL cross-connect. A VLL path can be switched to a secondary standby pseudowire
at the endpoint node (T-PE) as well as at switching node (S-PE). This requires that a mechanism be
built-in to avoid creating loops in the path of the VLL service. This mechanism could be based on
the use of the new active/standby status bits and distributing them among the T-PE and S-PE nodes
to indicate which spoke SDP to activate for the end-to-end VLL path.

Pseudowire Redundancy for a VPLS Service

There are a number of scenarios which require that a set of redundant pseudowires originate or
terminate in a VPLS service at a 7x50 node. An example is when in
configured in T-PE1 and T-PE2 is a VPLS service while the service configured in the S-PE nodes
is an Ethernet VLL with pseudowire switching.
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7750 SR OS Services Guide
the service