Internet/Network Layer Protocols
Wikipedia describes the role of the Internet Layer as
"The network layer provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks while maintaining the quality of service, and error control functions."
IP encapsulates the datagrams (UDP) or segments (TCP) from the transport layer into IP packets that can be routed differently over the Internet (i.e. it is a connectionless protocol). Each packet contains the IP address of the recipient.
Other Network Layer Protocols
There are a number of protocols that run over IP including
They are still considered to be in the Network layer as they provide control information.
There are also some protocols that run under IP but above the data link layer including
Click on a protocol to find out more about that protocol.
Next: Data Link Layer