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In order to ensure the reliable transfer of data between computers, network protocols are responsible for carrying out many procedures:
data must be formatted and packaged for transmission;
the path that the data will follow must be determined;
the rate of data transfer needs to be regulated;
inbound data must be assembled in proper sequence and screened for duplication;
the sender must be informed of the volume of data received successfully;
the data needs to be sent to the application for processing; and
errors or other problems must be handled properly.
In order to reduce the complexity of these functions, a layered model is used to provide a structure that is easy to reference and modify. As other protocols, TCP/IP uses a layered architecture that is described in more detail below.
Lower layers (Layers #1 and #2)
The lower layers are where device drivers and physical signals are handled. Data is packaged into units called frames or packets and sent onto the physical network. By keeping the lower layers separate from IP itself, a new type of network interface card can be added to a computer without affecting the protocol stack. In addition, IP can share a single network adapter with multiple other protocols. For example, TCP/IP and IPX can share a single token ring interface.
IP network layer (Layer #3)
This layer is responsible for routing data between host systems. The data may flow over a single physical network or...