I would Start At Optical Carrier-1 which means 55Mbps a Line, scales all the way up to OC-48 I read in one of my old Network+2003 Certs!
ISDN is Intergrated Service Digital Node which is Faster than Dial-up 56Kbps vs. 64Kbps/128Kbps two different types ISDN-A/ISDN-B which has something extra than ISDN-A!
DSL is either Symetrical 10Mbps/10Mbps Upload/Download or Asymetrical Lower Upload Speed than Download Speed. PPPOE needs Username/Password Name
Cable Was Faster Than DSL and had less Software problems with OS and Applications! Best to install their software and get their proxy server (Acts like a Guardian Trying To Filter Malicious Code) slows down connection not to much but gives you more insurance of Spyware /Adware/Trogan Viruses & PC/Browsers Hijackers!