Is it posible to see the link utilization on a router's serial interface with LMS 3.1?
If yes, please explain.
Yes. You can use the Health and Utilization Monitor plug-in module to do this. HUM ships as a 90-day eval along with LMS 3.1.
To do this in HUM, you would need to create an Interface Utilization poller under HUM > Poller Management.