Encapsulation Hierarchical layering of data. Data from application placed in packet with a TCP header. IP layer adds IP header and passes IP datagram to Ethernet.
Ethernet adds header and CRC to create frame for transmission.
Reciever then processes and removes headers in reverse order. Router based scheme. If packet too large for next hop, then need to fragment. Fragments are viewed as multiple physical packets, but one logical datagram. Data is split between fragments.