PS (Pseudowire Services) interfaces experience flapping and L2 neighbor instability when output-traffic-control-profile is applied to logical interfaces during configuration commits on MX Series routers. The CoSD (Class of Service Daemon) rejects the unsupported configuration, causing interface state changes and service disruption. This issue occurs because output-traffic-control-profiles are not supported on PS interface logical units (IFLs), and attempting to apply them triggers daemon errors that result in interface flaps affecting L2 adjacencies.

Network operators observe the following symptoms when this configuration issue is present:

• PS interfaces flap repeatedly during configuration commits
• Multiple L2 neighbors lose adjacency simultaneously
• CoSD daemon generates error messages in system logs indicating unsupported configuration

The following syslog messages appear in /var/log/messages when commits are performed:

COSD_TCP_ON_INTF_NOT_SUPPORTED: Output Traffic-control-profile is not allowed for IFL ps11.2609
COSD_TCP_ON_INTF_NOT_SUPPORTED: Output Traffic-control-profile is not allowed for IFL ps12.2608
COSD_TCP_ON_INTF_NOT_SUPPORTED: Output Traffic-control-profile is not allowed for IFL ps15.2619

Configuration shows output-traffic-control-profile applied to PS interface units:

show configuration interfaces ps11
unit 2609 {
    output-traffic-control-profile PROFILE_NAME;
}

Interface status shows repeated up/down transitions correlated with commit operations. L2 protocols (L2TP, L2VPN) experience session resets affecting connected neighbors.

This is a configuration error. Output-traffic-control-profiles are not supported on PS interface logical units.

Resolution: Remove the output-traffic-control-profile configuration from all affected PS interfaces:

delete interfaces ps11 unit 2609 output-traffic-control-profile
delete interfaces ps12 unit 2608 output-traffic-control-profile
delete interfaces ps15 unit 2619 output-traffic-control-profile
commit

After removing the unsupported configuration and committing changes, verify that:

1. No CoSD errors appear in system logs
2. PS interfaces remain stable
3. L2 neighbor adjacencies are maintained during subsequent commits

Note: If QoS functionality is required for these circuits, contact Juniper Professional Services or a certified partner to design and validate an appropriate QoS solution for PS interfaces in a proof-of-concept environment before production deployment. TAC does not provide configuration design recommendations for production networks.