Bearer circuit

Hi, I have a question about leased line bearer circuits, (if thats the correct description?), I'd be grateful if anyone can explain in simple terms the difference between, say,
a '20Mb line on a 20Mb bearer' & '20Mb line on a 100Mb bearer'?
What would be the actual difference you would see when using the internet? I suspect the short answer is 'faster' but the 20mb bearer is cheaper so its something I'm considering.
Thanks,

You would see no difference.

The 100Mb bearer is one that could provide a faster throughput but you will only have access to 20Mb of bandwidth.

The 100 Mbps bearer has the advantage of an upgrade to faster speeds should be easier in the future.

A bearer circuits is one which transports one or more smaller capacity circuits or channels. In this case a 100mbits bearer is being used to transport a 20 Mbits circuit. In part this maybe to allow for quick upgrade to the full bearer circuits speed, or to carry additional circuits, but probably because the most common sized circuits are either 10Mbits or 100Mbits.

thanks for your replies, thats perfectly clear.

Sometimes it can be used to offer burst speeds. Where I work one of our lines is 10meg burtsable up to 100.