• Network layer
  

Network layer is the
third lowest layer in the seven layer model. It handles moving packets between devices that are more than one link away from each other. So it makes routing decisions and forwards packets as necessary to help them travel to their intended destination. That's why we can say this is the layer which is responsible for translating the logical network address and names into their physical address (MAC address).

To complete its process the network layer translates logical network addresses into physical machine addresses. This helpful to determines the quality of service. In the same time this layer aids to route a message that will take if there are several ways a message can get to its destination.

In larger networks we can see that there may be intermediate devices and sub networks between any two end systems. The network layer makes it possible for the and layers above it to send packets without being concerned with whether the end system is on the same piece of network cable or on the other end of a large wide area network.

This layer split large packets into smaller chunks if the packet is larger than the largest data frame the Data-Link layer will accept. Then network reassembles the chunks into packets at the receiving end.

Network layer includes,

• Protocol
  
  • IP ( Internet Protocol)
    
  • IPSec ( Secure IP )
    
  • ICMP( Internet Connection Message Protocol )
    
  • Router    etc.
    

Functions and Services

 

• Connection model: connection-oriented and connectionless communication
  
• Host addressing
  
• Message forwarding
  
• Path determination
  
• Switching
  
• Call setup
  
• Data congestion