How does Juniper use shapers to help manage congestion?
Shaping is the application of a limit to the rate at which traffic can be transmitted. Unlike policing, it acts on traffic that has already been granted access to a queue but which is awaiting access to transmission resources. Traffic that does not conform to the shaper’s criteria is generally held in the queue until it does conform, and no explicit constraint is placed upon more traffic entering the queue (as long as the queue isn’t entirely full). Therefore, shaping can be less aggressive than policing and can have fewer of the negative side effects.
With Junos OS, you can apply a shaper to an entire port or to individual queues.