What's the difference between 'line rate' and 'throughput'?

Line rate is the maximum rate your telephone line will physically support.
It is determined by a number of factors:

• How near you live to the exchange (i.e. line length).
• The quality and length of any telephone extension cables in your home.
• The speed and quality of your router or modem.
• The speed of your computer.
• Whether all broadband micro filters are correctly installed.

Once set, your line speed remains largely stable, only changing if one of the above factors changes significantly. By contrast, Throughput is the speed of data flowing through your broadband connection at any one time. It is determined by:

• The speed of the Internet and of websites you are visiting.
• General Internet congestion.
• Whether you're sharing your broadband connection with others in your home.
• Whether you have spyware or adware slowing down your computer's speed.

Throughput speed is limited by the physical maximum speed of your phone line (line rate) and varies throughout the day, typically reducing during peak periods (6 - 11pm)