Line rate is physical (sync) speed at which you router communicates with the equipment directly connected to the other end of the telephone line in the exchange. It is determined by a number of factors:

  • How near you are 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.
  • 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.


Throughput is the speed of data flowing through your broadband connection at any one time. This is effectively the speed which you are actually receiving over you connection when downloading files, streaming video, etc. It is determined by:

  • The sync speed of the line (see the section above)
  • General Internet congestion, which typically is at its highest between 6pm and 11pm in the evening
  • The speed of the websites which you are visiting.
  • Whether you are sharing your broadband connection with others in your home (if you are using a wireless connection then you may also want to check your wireless security settings)
  • Whether you have spyware or adware slowing down your computer’s speed.
  • Off Network (BT Wholesale) lines also have an IP Profile which is set by BTW’s Dyanmic Line Management system

If you believe that your Internet connection is running slow then you may wish to read our guide here.