Network Layer - Introduction, Functions and Protocols

Network layer Introduction                

• In the seven-layer OSI model, the network layer is layer 3 which defines communication between the different networks and most commonly known as the layer where routing takes place.

Network Layer Functions

• Router is the device which works at this layer and the main job is to get packets from one network to another.

• Network layer communication also relies on protocols, these are as follows:

• At the Network Layer, the data is in the form of Packets (or also called as Datagram).Two types of packets are used at the Network layer: data and route updates.

  Data packets

Data packets are used to transport the user data across the network. Protocols used by the data packets are known as routed protocol. For example IP and IPv6  

Route update packets

These packets are used to update routers information within the internetwork. Protocols that send route update packets are called routing protocols; for example RIP, RIPv2, EIGRP, and OSPF

  Format of Packet

(Note: - This information is not limited to find blog on packet format)

• Basic introduction of IP (or logical Introduction)

  The dominant internetworking protocol in the Internet Layer in use today is IPv4. The successor to IPv4 is IPv6.

  Version 4 IP address is 32 bits long. When we refer to the IP address we use a dotted-decimal notation, while the computer converts this into binary. IPV4 addresses are divided into two parts(NetID&HostID)

Network Identifier (Network ID): A certain number of bits, starting from the left-most bit, are used to identify the network. This is also sometimes called the network prefix or even just the prefix.

Host Identifier (Host ID): The remainders of the bits are used to identify the host on the n/w.  

IPV4 addresses are categorized into classes, which are as follows:-  

Class A addresses range from 1-126.

Class B addresses range from 128-191.

Class C addresses range from 192-223.

Class D addresses range from 224-239.

Class E addresses range from 240-254.  

Note:-0 [Zero] is reserved and represents all IP addresses.

127 is a reserved address and is used for testing, like a loopback on an interface.

255 is a reserved address and is used for broadcasting purposes.  

(Note: - This information is not limited to find blogs on IPV4 & IPV6)

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