4.5 Automatic Protection Switching (APS) Configuration

The APS module implements the protocol and linear protection switching mechanisms for point- to-point VLAN-based ETH SNC in Ethernet transport networks. APS is defined by the ITU G.8031 standard.

The APS Configuration page allows the user to create and configure an APS Instance.

To create and configure an APS Instance, perform the following steps:

1. Go to Configuration > APS. The APS Configuration page appears.

   

   The list of parameters in this page are as follows:
   • APS #: The ID of the APS. The maximum number of creatable APS instances is 6. Click on the link to get to APS instance page, reset counters, and issue commands.
   • Port: The port to which this flow is attached
   • SF Trigger: Selects whether Signal Fail (SF) comes from the link state of a given port or from a Down-MEP
   • SF MEP: The Domain: Service::MEPID refers to a MEP instance which represents the Working flow. Only used when SF Trigger is MEP. The selected MEP instance does not need to exist when this APS is configured.
   • Mode: In the linear 1:1 protection switching architecture, the protection transport entity is dedicated to the working transport entity. However, normal traffic is transported either on the working transport entity or on the protection transport entity using a selector bridge at the source of the protected domain. The selector at the sink of the protected domain selects the entity which carries the normal traffic.
     • 1+1 Uni: This will create a 1+1 Unidirectional APS
     • 1+1 Bi: This will create a 1+1 Bidirectional APS

     In the linear 1+1 protection switching architecture, a protection transport entity is dedicated to each working transport entity. The normal traffic is copied and fed to both working and protection transport entities with a permanent bridge at the source of the protected domain. The traffic on working and protection transport entities is transmitted simultaneously to the sink of the protected domain, where a selection between the working and protection transport entities is made based on some predetermined criteria, such as server defect indication.

   • Level: MD/MEG Level (0–7)
   • VLAN: The VLAN ID used in the L-APS PDUs. 0 means untagged.
   • PCP: PCP (priority) (default 7). The PCP value used in the VLAN tag unless the L-APS PDU is untagged. Must be a value in range 0–7.
   • SMAC: Source MAC address used in L-APS PDUs. This must be a unicast address. If all-zeros, the switch port's MAC address is used.
   • Rev: When checked, the port recovery mode is revertive, that is, traffic switches back to the working port after the condition(s) causing a switch has cleared. In case of clearing a command (e. g. forced switch), this happens immediately. In case of clearing of a defect, this generally happens after the expiry of the Wait-To-Restore (WTR) timer. When unchecked, the port recovery mode is non-revertive and traffic is allowed to remain on the protect port after a switch reason has cleared.
   • TxAps: Choose whether this end transmits APS PDUs. Only used for 1+1, unidirectional.
   • WTR: When Rev is checked, WTR tells how many seconds to wait before restoring to the working port after a fault condition has cleared. The valid range is 1–720.
   • HoldOff: When a new (or more severe) defect occurs, the hold-off timer is started, and the event is reported after the timer expires. HoldOff time is measured in milliseconds, and valid values are in the range 0–10000. Default is 0, which means immediate reporting of the defect.
   • Enable: The administrative state of this APS instance. Check to make it function normally and uncheck to make it cease functioning.
   • Oper: This field cannot be configured but shows the operational state. Click on the link in the APS

     # field to get more details on the status.

     – : APS instance is functional

     – : APS instance is not functional

   • Warning: If the operational state is Active, then the APS instance is active, but it might not run

     the way the administrator thinks because of configuration errors, which are reflected/indicated in the following warnings.

     – : No warning

     – : Warning

     Use the tooltip to get the detailed warning information.

2. To configure the APS module, click the + icon on the bottom right corner of the APS configuration page (see the preceding figure). The APS Configuration table appears.