CFM OAM QoS

It is important that CFM OAM tools use the relevant FC and the associated queue to report traffic performance issues such as delay, jitter, and loss. When user traffic is mapped to one FC/queue and the OAM traffic is mapped to another FC/queue, data reported by the OAM tools might not be a true reflection of the performance metrics that the user traffic is experiencing, due mainly to different queue depths and scheduling priorities.

In order to ensure that CFM OAM traffic experiences the same treatment as user traffic, the 7705 SAR supports a configurable priority to specify the FC, and therefore the queue, to be used for a specified OAM test. The priority keyword in the eth-cfm loopback, one-way-delay-test, single-ended-loss-test, two-way-delay-test and two-way-slm-test commands is used to configure the FC mapping as per the configured priority. The priority value maps to a specific FC; therefore, selecting a priority selects the FC. Table: Y.1731 Priority-to-FC Mapping lists the priority-to-FC mapping. This mapping of priority to FC cannot be changed by the user.

The priority-to-FC mapping does change depending on the message type and direction of the MEP. Table: Priority Mapping Based on Message Type and MEP Direction summarizes the FC and Dot1p priority mappings based on this criteria.

For more information, see the 7705 SAR Services Guide, "Priority Mapping (802.1ag and Y.1731)".