At the receiving end the receiver reverses the process so the bits are received at the physical layer
by the network interface card or Nick the layer to head is red.
It is then stripped and the data is passed to layer three layer three head is red and that's stripped
and the data is passed to layer for.
And this process continues until all the headers have been removed.
So this is the process of D encapsulation where the head is a stripped and the data is passed up through
the OS on model until only the original data remains without any headers.
This data would then be processed by an application on that P.C. or in this example the web server.
So the web server would process the HDP get message sent by the browser on the client as an example.
So in summary please note that on the sender the data is transmitted down through the OS on model and
encapsulated at each layer and then physically transmitted across the wire at the receiver.
The data is d encapsulated at each layer of the OS on model until we have the original data which is
then used by the application.
So what's important to note is that because of encapsulation and d encapsulation each layer of the OS
I model only communicates with the equivalent layer on the other device.
So in this example PCI A's application layer communicates with PCI B's application layer.
This is true for all the other layers the presentation layer communicates with the presentation layer
session with session transport with transport and so forth and so on each layer only communicates with
the equivalent layer on the other device at the physical layer.
The data is transmitted as bits.
So as an example if we use Ethernet electrical current may be used to transmit zeros and ones.
Now specific terms are used in networking to refer to each layer.
So at the physical layer the data is transmitted as bits at the data link layer.
It's known as friends at the network layer.
It's known as packets and at the transport layer.
It's known as segments so in other words PDA transmits packets to PCV at the network layer at the data
link layer.
For example frames are transmitted and so forth and so on.
It's important that you understand these terms because in networking and in this course we'll talk about
how packets are routed by routers or how frames are transmitted through switches.
And that's because routers reside at Layer 3 of the OS model and switches reside at Layer 2.