If yes, then where? in the above described transport network?

At any router level, if it’s not L2 (doing briding, etc.). But per definition, in OSI, a router is by default, not specified, a L3 device.

In the internet. The routing is not done by our help but requires other guys, ISP, to do it for us.

At any switch, if the swith is L3. But if it is not specified, a switch is by default, following the standard, a L2 device…