Network Layer in OSI Model: Protocols, Examples, Functions

What is Network Layer

Definition: Network layer offers the management to handle the operation of subnet. Network layer helps to transfer the all packets from source to target point across several hosts over the network. Network layer is not required for connecting two computer systems with similar link. It forwards all signals through various channels to another point and it plays the role as network controller.

Network layer spits the all outgoing message into small units (packets) and assemble incoming packets into messages form for forwarding to higher levels.

Network Layer Operations

network layer

It helps to convert all logical network address into physical address format.

Gateway, routers, and other devices are used in the network layer, but network layer offers all mechanism for best routing the packet to destination point.

Breakdown enlarges packets into tiny packets format.

Protocols of Network Layer

There are different types of protocols which are used in the network layer; below explain each one –

List of Network Layer Protocols

  • CLNS (Connectionless-mode Network Service)
  • DDP (Datagram Delivery Protocol)
  • EGP (Exterior Gateway Protocol)
  • EIGRP (Enhanced Interior Gateway Routing Protocol)
  • ICMP (Internet Control Message Protocol)
  • IGMP (Internet Group Management Protocol)
  • IPsec (Internet Protocol Security)
  • IPv4/IPv6 (Internet Protocol)
  • IPX (Internetwork Packet Exchange)
  • OSPF (Open Shortest Path First)
  • PIM (Protocol Independent Multicast)
  • RIP (Routing Information Protocol)

Examples of Network Layer Protocols

CLNS (Connectionless-mode Network Service): It is also known as “Connectionless Network Service” that is used as datagram service in the OSI network layer and it doesn’t need any circuit to be built before transmitting data. CLNS is an service that is offered by CLNP (Connectionless-mode Network Protocol), so it is mostly implemented in several telecommunications networks over the world.

DDP (Datagram Delivery Protocol): It is a segment unit of the Apple Talk networking protocol suite that helps to transfer all datagrams with using of socket to socket over the AppleTalk Network. This protocol is more comfortable for those applications which do not need reliable delivery of data.

EGP (Exterior Gateway Protocol): EGP is an protocol that is used for swapping all routing information in between two nearby gateway hosts over the network of autonomous systems. The routing table has list of known routers as well as addresses, and these routing table information help to select best route from all available routes.

EIGRP (Enhanced Interior Gateway Routing Protocol): EIGRP is an dynamic routing protocol, and its main objecting of it is to identify better path in between multiple paths as well as delivering  the packets on them. It uses the 88 number protocols and it works over the network layer protocol in OSI model.

ICMP (Internet Control Message Protocol): ICMP protocol is used by network devices for determining the all network communication issues and errors as well as monitoring that all data is arriving  its appropriate target point with its timing duration or not. This protocol is also used in the distributed denial-of-service (DDoS) attacks.

IGMP (Internet Group Management Protocol): IGMP protocol is used to manage group membership in the multicast network. In a multicast network, several routers are used which help to guide route packets for all computers which are associated with particular group. Multicast routers grab all information from IGMP to identify all hosts which are getting membership of group.

IPSec (Internet Protocol Security): IPSec is a set of protocols, and they are used to establish encrypted connections in between multiple devices. It offers security feature to send data over the public network system.  IPSec is mostly implemented to configure VPN set up and it helps to work by encrypting IP packets.

IPv4/IPv6 (Internet Protocol): IPv4 is the fourth version of internet protocol and IP means internet protocol. It contains 32 bit integers along with four addresses that is expressed into hexadecimal format like as

IPv6 is sixth generation of internet protocol, and it was developed by Internet Engineering Task Force (IETF) in December 1998. It uses the 128 bit internet addresses with eight groups of four hexadecimal digits like as 2001:0da8:75a3:0000:0000:8a2e:0370:8543

IPX (Internetwork Packet Exchange): IPX was released in 1980s, but it was getting popularity through 1990s. It is networking protocol that is used by Novell NetWare operating system and after some time it was adopted by Windows.

OSPF (Open Shortest Path First): OSPF is designed by Internet Engineering Task Force (IETF) and it works as Interior Gateway Protocol (IGP). It is a link state routing protocol and it helps to find best path in between the source and target router.

PIM (Protocol Independent Multicast): PIM helps to distribute the multicast data with using of routes that is gathered by other protocols.  It uses the unicast routing table for making and maintaining the multicast routing trees with using of reverse path forwarding. PIM has two variants PIM-Dense Mode and PIM-Sparse Mode.

RIP (Routing Information Protocol): RIP is an dynamic routing protocol that is used the hop count (number of routers occurring in between the source and destination network) like as routing metric for finding the best route in between the source and destination point.

Functions of Network Layer

Network layer’s functions are divided into four different areas; such as-

Routing System: It is main part of the network layer because it helps to identify better optimal path from the several paths source to target point. When router grabs all packets via its input link, then it will transfer those packets to router’s output link. For instance; if packet tries to move M1 to N1 then it must be transferred to further router via path to M2.

Addressing System: Network layer uses the logical addressing because this address helps to identify source and destination point. Network layer appends the logical addresses to the header of the frame.

Internetworking System: The main objective of network layer is to provide logical connection in between the distinguish kinds of networks and network’ devices.

Segmentation: In this process, to break all packets which are received from upper layer into small segments. This process is also known as “Packetizing” and it is done with the help of internet protocol (IP).