Session DNS

DNS (Domain Name System)
==========================
The Domain Name System (DNS) is the phonebook of the Internet.
google.com--> 121.123.23.212

Web browsers interact through Internet Protocol (IP) addresses. DNS translates domain names to IP addresses so browsers can load Internet resources.



How DNS works:
https://www.youtube.com/watch?v=2ZUxoi7YNgs


OSI Layer
============
7 Layers:

Sender                                  Receiver
=======                                 ========

7. Application Layer                7. Application Layer

6. Presentation Layer               6. Presentation Layer

5. Session Layer                    5. Session Layer

4. Transport Layer                  4. Transport Layer

3. Network Layer                    3. Network Layer

2. Data Link Layer                  2. Data Link Layer

1. Physical Layer                   1. Physical Layer
       | 								                 ^
       |                                 |
       |------------->---->----->--------|


Application Layer: All applications and utilities that communicate with network fall in this layer.
Like your Browser...

Presentation Layer:
This layer is usually part of an operating system (OS) and converts incoming and outgoing data from one presentation format to another -- for example, from clear text to encrypted text at one end and back to clear text at the other.

Session Layer:
This layer sets up, coordinates and terminates conversations. Its services include authentication and reconnection after an interruption.

Transport Layer:
This layer manages packetization of data, then the delivery of the packets, including checking for errors in the data once it arrives.    (TCP AND UDP)
-->Segmentation
-->Connection management
-->Reliable and unreliable data delivery




Network Layer:
This layer handles addressing and routing the data -- sending it in the right direction to the right destination on outgoing transmissions and receiving incoming transmissions at the packet level.
Network layer is responsible for providing logical address known as IP address. Router works on this layer. Main functions of this layer are following:-
-->Define IP address
-->Find routes based on IP address to reach its destination

Data link Layer:
It forms frames from the packets that are received from network layer and gives it to physical layer.Outgoing messages are assembled into frames.
--> Defining the Media Access Control (MAC) or hardware addresses
--> Defining the physical or hardware topology for connections
--> Defining how the network layer protocol is encapsulated in the data link layer frame


Physical Layer:
All the transmission of data in a network is done in 0 and 1 so that converion is done over here .


TCP/IP Model:
===============
4 layers

Sender                                  Receiver
=======                                 ========

4. Application Layer                4. Application Layer

3. Transport Layer                  3. Transport Layer

2. Internet Layer                   2. Internet Layer

1. Network Interface                 1. Network Interface



OSI -    protocol independent,TL guarantees delivery of packets
TCP/IP - based on standard protocol,TL does not






Web Technology Basics
=======================
Domain Name
Hosting Spaces
Server
Client
Backend (Database)
Front end
Browsers