The third layer of the osi reference model is network layer. It is responsible for providing functions for a logical topology of your network using logical addresses.
The network layer provides services for the delivery of packet from source to destination possibly across multiple networks. However, data link layer connects hosts within same network. In network layer, frames are modified to data packets. The layer 3 makes best effort delivery of packets from source to destination.
For the packet delivery the hosts are assigned address and the layer 3 performs routing functions. The network layer provides a defined benefit services for switching connections and packet-oriented services for the relaying of data packets. The data transmission in both cases will go over the entire communication network and includes the route search (routing) between the network nodes.
The layer 3 translate the logical address into physical addresses. The main role of the network layer is to move the packets from sending host to the receiving host. This layer has the responsibility to route the packets from source to destination, mapping different addressing schemes and protocols. See the image below.
Functions of network layer
- Defines logical addresses used at layer 3.
- Finds paths based on the network numbers of logical addresses, to reach destination components.
- Breaking up data into network packets and reassembling data on the receiving end.
- Routing packets from one place to another by finding the best path across the physical network.
- This layer offers a logical connection between multiple types of networks.
- Data switching which is a procedure of changing packets from source to destination hub.
Network layer protocols
- DDP Datagram Delivery Protocol
- DVMRP Distance Vector Multicast Routing Protocol
- ICMP Internet Control Message Protocol
- IGMP Internet Group Management Protocol
- IPsec Internet Protocol Security
- IPv4/IPv6 Internet Protocol
- PIM-DM Protocol Independent Multicast Dense Mode
- PIM-SM Protocol Independent Multicast Sparse Mode