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Configuring Continuity Check Messages

 

Junos OS provides enhancements to trigger faster protection-switching and convergence in the event of failures in Ethernet domains for Carrier Ethernet services. These enhancements can be used when CE devices in the Ethernet domain detect faster service failures and propagates the information in the interface-status TLV of the continuity-check messages (CCMs). When CCMs are received, PE devices can perform certain actions which facilitates faster protection-switching and convergence. You can configure CCM for better scalability using the information provided in this topic.

Configuring Faster Protection Switching for Point-to-Point Network Topologies

You can apply an action profile to provide faster protection switching for point-to-point network topologies with local switching configured. In a normal state, CCM sessions are configured on the working and protect interfaces. The CCM packets transmitted contain an interface-status TLV with the value up on the working interface and value down on the protect interface. When a link fails on the working interface, the protect interface starts receiving the interface-status TLV as up. With the profile configuration, if the interface-status TLV received on the protect interface is up, the working interface is automatically marked as interface-down.

To configure the interface-status-tlv down event, include the interface-status-tlv down statement at the [edit protocols oam ethernet connectivity-fault-management action-profile profile-name event] hierarchy level.

To configure interface-down as the action profile’s action, include the interface-down statement at the [edit protocols oam ethernet connectivity-fault-management action-profile profile-name action] hierarchy level.

To configure interface-down peer-interface as the clear-action, include interface-down peer-interface at the [edit protocols oam ethernet connectivity-fault-management action-profile profile-name clear-action] hierarchy level.

In this action profile configuration, when the interface-status TLV is received as up, the peer-interface is marked as down.

The peer-interface is configured in the protect-maintenance-association statement. Consider the following example using the protect-maintenance-association statement in the configuration:

Configuring Faster Convergence for Dual-Homed Multipoint-to-Multipoint Network Topologies

You can apply an action profile to provide faster convergence for dual-homed multipoint-to-multipoint network topologies. If a multipoint-to-multipoint Ethernet service uses MAC-based forwarding and stale MAC addresses exist in the learning tables, this can result in traffic black holes in the network where incoming traffic is silently discarded, without informing the source that the data did not reach its intended recipient. With the profile configuration, if the interface-status TLV received on the protect interface is up, then the interface-status TLV on the working interface is marked as down and the PE device for the protect interface propagates a remote MAC-flush message to the PE devices in the virtual private LAN service (VPLS) by using TLDP-MAC-FLUSH. The MAC flush avoids traffic blackholing due to stale mac-db entries.

To configure the interface-status-tlv down event, include the interface-status-tlv down statement at the [edit protocols oam ethernet connectivity-fault-management action-profile profile-name event] hierarchy level.

To configure propagate-remote-flush as the action profile’s action, include the propagate-remote-flush statement at the [edit protocols oam ethernet connectivity-fault-management action-profile profile-name action] hierarchy level.

To configure propagate-remote-flush as the clear-action, include the propagate-remote-flush statement at the [edit protocols oam ethernet connectivity-fault-management action-profile profile-name clear-action] hierarchy level.

In this action profile configuration, when the incoming CCM packet contains the interface-status TLV with value down, the propagate-remote-mac-flush action is triggered for the action-profile.

Configuring a Primary VLAN ID for Increased Flexibility

You can assign a primary virtual LAN (VLAN) ID in the maintenance association for increased flexibility in the number of tags. When a vlan-range or vlan-id-list is configured on an interface, the service OAM must run on one of the VLANs. The VLAN assigned for service monitoring is considered the primary VLAN. If a primary-vid is not configured, Junos OS assigns the first VLAN from the vlan-range or vlan-id-list. In earlier releases, Junos OS assigned VLAN 4095.

To configure a primary VLAN ID, you can specify the primary-vid statement at the [edit protocols oam ethernet connectivity-fault-management maintenance-domain domain-name maintenance-association ma-name] hierarchy level:

Configuring a Remote Maintenance Association to Accept a Different ID

You can configure a maintenance association to accept a different maintenance association identifier (ID) from a neighbor by including a remote-maintenance-association statement. The 802.1ag CCM sessions expect the same maintenance association identifier from its neighbors. If there is a maintenance association identifier mismatch, the PDUs are marked as error PDUs. If a remote-maintenance-association statement is configured, a different maintenance association identifier is accepted and the 802.1ag CCM sessions do not mark the CCM PDUs as error PDUs when the maintenance-association name is the same as the name specified in the remote-maintenance-association statement.

To configure a remote maintenance association, include the remote-maintenance-association statement at the [edit protocols oam ethernet connectivity-fault-management maintenance-domain domain-name maintenance-association ma-name] hierarchy level:

Using this configuration, interoperability is improved for CCMs with low-end CE devices supporting fixed maintenance association identifier configurations.