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What Is Function Of Network Layer?

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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.

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