Transport layer
Internet layer
Network access layer
Physical layer
Now the record is sent to the transport layer.
The transport layer is concerned with data quality and reliability. It checks for errors and determines to which application the data must go. This is determined by a port number, that is added to the front of the record. The header is the data added at each level which is specific for interpretation at that level. Together, this data is called a segment. TCP provides this function.
Next the PDU(Protocol Data Unit), or combination of header and data, is passed on to the Internet layer.
The Internet layer is served by the IP(Internet Protocol), which uses an IP address to locate another host on another network and find it's way there.
This PDU is called an IP datagram, which is sent to the network access layer.
The network access layer, controls data exchange between the host and it's network. Data sent at this level is called packets. The programs used for control at this level are determined by the type of network in use.
The packets are sent through the physical layer, or the actual connections between the host and the network.
When the data reaches the other side, it is dissected and sent up each layer in reverse order, stripping away and using the headers at each necessary level until it reaches it's destination application.