Example Trace Process 1 of Host A => P2 of B
process 1 hands msg to TCP with dest. P2 of B
TCP may break msg into a number of frames
each frame has Dest Port (ie process P2)
Sequence Number (so can be ordered)
TCP hands to IP for sending to B
IP datagram with Dest Host, ie, B, created & sent, possibly via several networks
each IP datagram handed to Network Access layer for 1st, etc, network. contains Dest Subnet address, priorities, etc.