The network layer provides end-to-end communication to the transport layer, contrasting with the data link layer which offers node-to-node service. The internet, or internetwork, is a collection of interconnected networks facilitating data transmission through packet switching. Routers operate at the network layer, directing packets along optimal routes and processing only those messages specifically addressed to them.

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NETWORK
LAYER
Dr. C.V. Suresh Babu

2. • The function of the network layer is to provide an
end-to-end communication capability to the
transport layer, which lies above it
• The main difference between the data link layer and
the network layer is that the data link layer provides
a reliable node-to-node service between adjacent
nodes and the network layer provides a reliable end-
to-end service between the source and the
destinations.
2

3. 3
The internetwork is the
Collection of networks
interconnected by routers and
other devices that function
generally as a single network.
This whole network is called
the Internet. The other name
of the internet is Internetwork.
The Internet is the
simplified name of the
internetwork.
Internetworks

4. 4
It is a mode of data transmission in which a message
is broken into a number of parts which are sent
independently, over whatever route is optimum for
each packet, and reassembled at the destination.

5. 5
An IP address (internet protocol address) is a
numerical representation that uniquely
identifies a specific interface on the
network.

6. 6

7. SUBNETTING
7
Subnetting is the practice of dividing a network into two or
more smaller networks. It increases routing efficiency,
enhances the security of the network and reduces the size of
the broadcast domain

8. 8

9. ROUTING
9
Routing is a process which is performed by network
layer devices in order to deliver the packet by choosing
an optimal path from one network to another.

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12. 12
Routers)
• Routers operate at the network layer, connecting two or
more network segments that may different data link layer
protocols, but the same network layer protocol.
• They can also connect different types of cabling.
• Router operations involve stripping off the header and trailer
of the incoming data link layer frame and then examining the
destination address of the network layer packet. The router
then builds a new frame around the packet and sends it out
onto another network segment.
• Another important router feature is that they choose the
“best” route for a packet to follow, hence the name ‘router’.
• This also means that routers need to perform more
processing than bridges or layer 2 switches.
• Another important difference is that, unlike a bridge, a router
only processes messages that are specifically addressed to it.

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Example of a Router