I can't understand what is meant by line-speed. From a networking point of view, we can say that line-speed is the number of packets transmitted in a unit of time.
I got this term from here:
link of line-speed term, the paper name is:
Software-Defined Networking: A Comprehensive Survey:
Open-source prototypes are available  as well as evaluation results showing the line-speed capabilities using a network processing unit (NPU)-based  proof of concept implementation.
Somebody, please guide me.