I remember when I connected to the internet via the phone line and a 56kbps modem, changing ISPs was as simple as changing the phone number dialled by the modem.
I remember that my IP address would change every 1 minute, without a break in connection. But I also remember downloading large files over HTTP, sometimes downloads would take hours to complete.
In a situation like this, how does the TCP connection remain open, while the IP address changes frequently?
Also, as a side question... I live in the UK, so it's all fibre optic and static IP's now, I'd be interested to know if other places in the world still rely on technology like this.