Layer 3 of the OSI model known as OSI Network Layer has a role to carry data from the source address to destination address regardless of the type of data. The protocols of the network layer specify addressing and processes that enable transport layer data to be packaged and transported. Usually we call this process end to end transport.
To accomplish this transport OSI network layer uses four basic processes such addressing, encapsulation, routing and decapsulation. Addressing is about mechanism that network layer must provide for addressing the end devices. Encapsulation is about adding a layer 3 header or label to layer 4 data and after encapsulation process we call this data as a packet. Routing is about services to direct the packet to destination, routing process will occur if the destination and source address not in the same network. Decapsulation is about removing layer 3 header before forwarding to layer 4.
Protocols implemented at the OSI Network layer that carry user data include: Internet Protocol version 4 (IPv4), Internet Protocol version 6 (IPv6), Novell Internetwork Packet Exchange (IPX), Apple Talk and Connectionless Network Service (CLNS/DECNet). The most widely-used protocol is Internet Protocol, others protocol maybe used for specific product with a minimal discussion.