Network Layer - Functions and Main Protocols

Network Layer is the third layer in OSI Reference model. It is responsible for providing a logical topology for a network by assigning IP addresses to every host. Providing logical addresses to networking devices is the duty of Network Layer. It also responds to service requests from Transport Layer and issues service requests to Data Link Layer. In the network layer, data is passing in the form of packets. It is responsible for establishing paths for data transfer between different networks while the Transport layer provides host to host communication. The router is the most important network layer device.

Functions of the Network layer

Important functions of the network layer are given below.
  1. Network routing

  2. Logical Addressing

  3. Network segmentation and De-segmentation

  4. Error handling

The network layer is responsible for assigning IP addresses and maintaining routing tables (Router does this function). Internet Protocol is responsible for assigning IP addresses to each and every networking devices in the network. It is also doing the function of adding control information to the data segments coming from Transport layer and sending it to Data-link Layer. It is also responsible for maintaining error-free network structure by assigning a unique IP address to each host.

Major Network Layer Protocols
  1. IPv4 (Internet Protocol version 4)

  2. IPv6 (Internet Protocol version 6)

  3. Datagram Delivery Protocol

  4. Internet Control Message Protocol (ICMP)

  5. Internet Group Management Protocol

  6. IPsec

  7. AppleTalk

  8. IPX

  9. XNS

OSI Structure
  1. Physical

  2. Data-link

  3. Network

  4. Transport

  5. Session

  6. Presentation

  7. Application

Major Network Layer Devices

Important network layer devices are:
  1. Router

  2. Layer 3 Switch

These two devices are in the third layer because both of them uses packets to communicate. These devices perform packet forwarding and routing based on routing protocols. Logical addressing is one of the most important features of the 3rd layer of the OSI Reference model. Since every device is getting a unique IP address, communication goes well without any issues.

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