This read-only string reports the SNA Class of Service (COS) name being used in the direction toward the session's secondary logical unit (SLU) for a session crossing an ISTG at this Extended Border Node. Admins check it to confirm which COS, and therefore which network path characteristics and priority, an active session is actually using toward its destination. For example, seeing an unexpected COS name here for a supposedly high-priority session would point an admin toward a COS mapping misconfiguration on this border node.