Industry standard bandwidth guarantee?

[ktokash at hotmail.com (keith tokash)]

Hi *, sorry if this has been answered, I did look.

Is there an industry standard regarding how much bandwidth an inter-carrier circuit should guarantee?  Specifically I'm thinking of a sub-interface on a shared physical interface.  I've not thought much about it but if there's a more generally-accepted guideline than, "when the customers start leaving / when you leave," I'm at least 5% ears.

Thanks,
Keith