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Reducing APS Switchover Time in Layer 2 Circuits

 

On M320 routers with Channelized OC3/STM1 Circuit Emulation PIC with SFP, you can configure the fast-aps-switch statement at the [edit interfaces interface-name sonet-options aps] hierarchy level to reduce the Automatic Protection Switching (APS) switchover time in Layer 2 circuits. Configuring this statement reduces the APS switchover time only when the Layer 2 circuit encapsulation type for the interface receiving traffic from a Layer 2 circuit neighbor is Structure Agnostic time-division multiplexing (TDM) over Packet (SAToP).

The fast-aps-switch statement must be configured on both working and protect circuits. Additionally, to achieve reduction in APS switchover time:

  • Per-packet load balancing must be configured.

  • Bidirectional switching mode must be configured.

  • If the fast-aps-switch statement is configured in revertive APS mode, configure an appropriate value for revert time. We recommend that you configure a revert time of 600 seconds for 672 through 1344 Layer 2 circuits.

  • To prevent the logical interfaces in the data path from being shut down, configure appropriate hold-time values on all the interfaces in the data path that support TDM.

Note
  • The fast-aps-switch statement cannot be configured when the APS annex-b option is configured.

  • The interfaces that have the fast-aps-switch statement configured cannot be used in virtual private LAN service (VPLS) environments.

The following tasks illustrate how to configure Junos OS to reduce APS switchover time.

Note

Per-packet load balancing can be configured for a limited set of routes or for all routes. To simplify the steps involved in configuring per-packet load balancing, steps for configuring per-packet load balancing for all routes is covered in this procedure.

Configuring Per-Packet Load Balancing

To configure per-packet load balancing for all routes:

  1. Configure the per-packet option for the load-balance statement at the [edit policy-options policy-statement policy-name then] hierarchy level.

    For example:

  2. Configure the policy name in the export statement at the [edit routing-options forwarding-table] hierarchy level.

    For example:

Configuring Fast APS Switchover

To configure fast APS switchover:

  1. On both the working and protect circuits, configure the fast-aps-switch statement at the [edit interfaces interface-name sonet-options aps] hierarchy level.

    For example:

  2. Configure bidirectional switching mode on both the working and protect circuits. To do this, configure the switching-mode bidirectional statement at the [edit interfaces interface-name sonet-options aps] hierarchy level on both the working and protect circuits.

    For example:

  3. If APS is configured in revertive mode, configure an appropriate value for revert time on both the working and protect circuits. To do this, configure the revert-time statement at the [edit interfaces interface-name sonet-options aps] hierarchy level on both the working and protect circuits.

    For example:

  4. To prevent the logical interfaces in the data path from being shut down, configure appropriate hold-time values on all interfaces in the data path that support TDM.

    For example: