Network Layer
Network layer is the third layer of the OSI Model. The Network layer forms the packets from the data received by the transport layer. The Network layer establishes the root between the sending and the receiving host. The Network layer deliver the packet from the one node in the one network to the destination node to the another network. The protocols use in the network layer uses the header that includes the source and destination addresses. This layer handles the routing of the data and the basic of the data in the Network layer is called the Packet.
The Network layer is responsible to deliver the data from source to the destination across multiple networks.
Responsibilities of the network layer-
1. The Network layer receive the data from the upper layer that is transport layer and and add the header to the packet include the logical address of the source and the destination.
2. Network layer provides the function of the routing means to route the packet from the sender to the receiver.
There are two types of packet used at the network layer-
Data Packet-used to transport user data through the internetwork .protocol are used to support the data traffic are called the routed protocol. Example of routed protocol is the IP, IPX.
Route update packets-these packets are used to update the neighboring routers. Protocol that send route update packet are called routing protocol –RIP, EIGRP, OSPF etc.
The network layer defined end to end delivery of the packets. It includes the logical address so that the destination point can be identified.
The Network layer performing four tasks-
1. Addressing the packet with the IP address.
2. Encapsulation
3. Routing
4. Decapsulation
Encapsulation and the Decapsulation occur at all the layer of the OSI Model. Routing is the process to route the packet from the source to the destination.
Router works on the layer 3 devices.
If the destination host in the same network where the source host exists, the packet is deliver between the two hosts without the need of the router. But if the destination host and the source host are not in the same network the packet carry transport layer PDU across many network and through many routers.
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