What Is Function Of Network Layer?

Network Layer Functions

Some
of the specific jobs normally performed by the network layer include:

• Logical Addressing: Every
       device that communicates over a network has associated with it a logical
       address, sometimes called a layer three address. For example,
       on the Internet, the Internet Protocol (IP) is
       the network layer protocol and every machine has an IP address. Note that
       addressing is done at the data link layer as well, but those addresses
       refer to local physical devices. In contrast, logical addresses are
       independent of particular hardware and must be unique across an
       entire internetwork. 


• Routing: Moving
       data across a series of interconnected networks is probably the defining
       function of the network layer. It is the job of the devices and software
       routines that function at the network layer to handle incoming packets
       from various sources, determine their final destination, and then figure
       out where they need to be sent to get them where they are supposed to go.
       I discuss routing in the OSI model more completely in this topic on the
       topic on indirect device connection, and show how it works by
       way of an OSI
       model analogy. 


• Datagram Encapsulation: The
       network layer normally encapsulates messages
       received from higher layers by placing them into data-grams (also
       called packets) with a network layer header. 


• Fragmentation and
       Reassembly: The network layer must send messages down to the data
       link layer for transmission. Some data link layer technologies have limits on the
       length of any message that can be sent. If the packet that the network
       layer wants to send is too large, the network layer must split the packet
       up, send each piece to the data link layer, and then have pieces
       reassembled once they arrive at the network layer on the destination
       machine. A good example is how this
       is done by the Internet Protocol. 


• Error Handling and
       Diagnostics: Special protocols are used at the network layer to
       allow devices that are logically connected, or that are trying to route
       traffic, to exchange information about the status of hosts on the network
       or the devices themselves.