Just to get the details correct...
Layer 1 Physical layer is your cable and the electricity and modulation and stuff
Layer 2 Link layer is Ethernet, which has the MAC addresses
Layer 3 Network layer is IP, which has IP addresses
Layer 4 Transport layer (Internet layer) is TCP, which has TCP ports
Layer 7 is for instance HTTP, which has URLs.
(Layers 5 and 6 are usually contained in layer 7)

Marius (Escort Cab + Mark II)