This OID stores the cost metric (on a scale of about -2 billion to +2 billion) for sending messages with a specific quality-of-service level over a particular logical line to an adjacent node. Engineers use this to make routing decisions—routes with lower cost metrics are preferred over higher-cost ones. For example, a value of 100 on one line and 200 on another tells the router that the first line is twice as attractive for that service type.