Are ISP links symmetric?

A slightly strange ask I know, but when an ISP purchases 21cn bandwidth charged per mbit, are they charged for a symmetric link of 'n'mbit, or must they separately purchase downstream and upstream bandwidth?

i.e. if Isp A buys 10mbit, would that mean that their customers could simultaneously download and upload at 10mbit in either direction? Or would the isp have to decide on a "split" (eg 9mbit down and 1mbit up)?

I know that for leased lines, they are symmetric, but I'm not sure how BT behave here!

I believe they are billed for "transit"; which means it is about the volume of data and not the transmission rate or direction.

ISPs rent throughput capacity (Gbps) on MSILs. I can't answer the original question though.

Yeah, i knew it was a cost per committed mbit and a further cost per burst mbit. I figured that the links would be symmetric, otherwise some of the wholesalers wouldn't be offering unmetered uploads, but i just figured it'd be nice to check!

But most uploads are small fry speedwise compared to downloads.

Hi

I have a 10 meg BT Leased line and I am billed for the capacity of the line not the amount of data transmission. I received a very good price on the line they have now approached me and offerd me a 500meg line uncontended with very good SLA'S as down time cost us lots of money also I believe this line has options for Asymetric use.

In reply to a post by blueacid:

I was telling DougM it isn't charged by data volume.

Typically yes, but i figured it was worth knowing