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End Devices in Network Layer

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The network layer is the third layer of the OSI model. Handles transport layer service requests and forwards service requests to the data link layer. The network layer translates logical addresses into physical addresses. It defines routes from sources to destinations, manages traffic issues such as switching and routing, and controls packet congestion. The main job of the network layer is to move packets from the sending host to the receiving host.

Addressing End Devices:

The task of identifying the various network devices falls within the network layer. The network layer keeps the logical address in the network. As a result, fixed addresses are not set to the devices and are therefore subject to change. Remote distribution is carried out using these addresses in this layer.

Routing:

Routing is a process that aids in giving direction to the data from the host to the destination at the network layer. The packets may need to pass through the network via numerous intermediary devices, like routers. The purpose of routing is to ensure the selection of the most effective route that takes to the destination. A destination host on another network can be reached by using services offered by the network layer. The processing of a packet occurs before it can move to other networks by a networking device-router. In other words, determining paths for packets to take and directing them toward the destination host are both parts that need to be taken care of in the routing method. A packet reaches the destination host by moving through several intermediary devices. A hop is the step a packet takes to reach its destination host.

Encapsulation:

The packet is the PDU-Protocol Data Unit of the network layer. Encapsulation includes supplementing the transport layer segments with information particular to layer 3. These include the headers and trailers. In other words, a Protocol Data Unit (PDU) is delivered from the transport layer to the network layer. Encapsulating the network layer refers to the addition of IP header information, such as the IP addresses of the source (sending) and destination (receiving) hosts. The PDU is known as a packet once header data has been appended. Additionally, it separates the transport layer pieces for distant distribution.

Decapsulation:

The decoding process occurs for the packet when it reaches its destination, then transfers up the OSI layers to the application layer and ultimately the human network. The transmission of packets is carried out by network layer, and it does not store data from higher levels, such as the type of application. The decapsulation is used for reassembling the packets into segments so that they can be used in the transport layer. The host looks up for the packet’s IP header when it reaches the network layer of the destination host. The IP header is dropped from the packet if its own IP address matches the destination IP address in the header. Basically, de-encapsulation is the term used to describe the elimination of headers from lower layers. The resulting Layer 4 PDU is then passed up to the proper service in the transport layer after the network layer has de-encapsulated the packet.

Network layer protocols:

The protocols used by the network layer specify the packet format and its processing from one host to another host, in contrast to the transport layer (OSI Layer 4) which regulates the transmission of data between the program running on each host. The network layer can carry packets for many forms of communications between various hosts by operating without regard to the data carried in each packet.

There are two main data transport protocols utilized at the network layer. As follows:

IP (Internet Protocol):

IP describes the steps needed to deliver a packet from the source device to the destination device through the network. Regardless of the number of nodes in the network, the IP address is constant. IP does not monitor or manage the movement of the various packets. These tasks are completed on other tiers. Some IP characteristics are included in the list below.

  • Connectionless refers to the fact that packets can be transferred without first establishing a connection.
  • Independent of the media used, such as wireless, copper line, or fiber optic, the IP address remains constant.
  • Unreliable delivery (Best effort) refers to the fact that packet delivery is not guaranteed. If a packet is lost in transit, it may be retransmitted depending on the protocols used at lower layers, such as the transport layer. For instance, because VoIP utilizes UDP, lost VoIP packets are not retransmitted; but, since HTTP uses TCP, lost HTTP packets must be retransmitted.

Conclusion:

The network layer, often known as OSI Layer 3, provides services that enable end devices to exchange data across networks. The network layer employs four key procedures to achieve end-to-end transport: addressing, routing, encapsulation, and decapsulation.


Last Updated : 20 Dec, 2022
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