We live in a world where every field requires use of computers. But computers need data to process the output. This data can be gathered with the help of internet. The internet uses World Wide Web to gather data. So the user must know the basics of the internet. So I am going to acknowledge the basic parts where and how the computer uses internet. I am going to discuss about OSI layers.
Osi means open system interconnect and was invented by ISO (INTERNATIONAL SYSTEM OF ORGANIZATION) which is an institution who manages giving standardization of the products to be manufactured. It was invented by iso in 1984. The use of iso in networking terms is to provide networking standardization of frame work for implementing network protocols to be used in seven layers.
The seven layers breaks down the process of communication into smaller and easier to handle independent categories. Before osi different networking vendors couldn’t communicate with each other. After iso now different vendors have the ability to converse with each other. Hence it is called platform independence
Now I will show you computers communicate with each other through the use of seven layers. Now lets get started
We will start from the layer 1 of seven layers and continue till the last layer. They are as under
1. Application layers
2. Presentation layers
3. Session layers
4. Transport layers
5. Network layers
6. Data link layers
7. Physical layers
Application layers helps us and is responsible to work with application layer softwares by which we use or access a network . Application softwares are
Google chrome, Mozilla firefox, Opera , Youtorrent Downloader, TDM etc.
APPLICATION PROTOCOLS EXAMPLE
HTTP, FTP, SMTP, POP3, NTP etc.
This layer works with file types means compression and decompression of file types as well as change one file type to other file types. It is also used data encryption and decryption too.
PICTURE : .jpeg, .bmp, .png, .gif
AUDIO : .mp3, .wav, .ogg, .flac, .amv
VIDEO : .MP4, .MKV, .AVI, .3GP, .MPEG
DOCUMENT: .DOCX, .XLSX, .PPT, .PDF, .TXT, .RTF, .HTML
Session layer is responsible for creating, managing and terminating a session, it also works with mode of communications.
The transport layer is responsible for what the actual mechanism of creating as well as terminating session where it can provide both reliable and unreliable data delivery. It is also responsible for error correction remember error correction is defined in this layer but error detection is done in network layer.
This layer has 5 main function
1. It tears down and sets up an session connection between two components.
2. It can provide reliable as well as unreliable data delivery
3. It segments or crops down data in smaller and manageable sizes.
4. It multiplexes connection allowing multiple application to send and receive data simultaneously on the same networking device
5. It also provides flow control and avoids congestion
Transport layer has two types of protocols.
Transmission control protocol
Transmission control protocol is a connection oriented reliable protocol because it gives acknowledgement. It is slow protocol the connection is eastablished by 3 way :-handshaking process.
Now I am going to tell you about port number which is used in Transmission control protocol.
It is also known as transport layer or layer 4 address. This number is used for protocol identification. It is a 16bit address maximum port number will be 216 = 65536. This number is controlled by internet assigned number authority (IANA).
IANA has grouped this number in 3 groups
1. Well known address
This address are registered and controlled by IANA. Range is (0 - 1023). To view this address go to RUN- %Systemroot% \system32 \drivers\etc\services. Open the file in notepad.
2. Registered Address
This addresses are registered and not controlled by IANA. Range is (1024-49151).
3. Dynamic Address
This addresses neither register nor controlled by IANA. It is automatically used by desktop computers. A range (49152-65535).
5. NETWORK LAYER
This layer defines the logical address of networking devices. It is also responsible for finding paths based on the network numbers of logical addresses to reach destination components. It connects different data link layer network types together such as serial, Ethernet, token ring etc.
This layer has two types of protocols
1. ROUTED PROTOCOLS
This protocol defines the source and destination address of data packet (where are the data packets are and where it will go) e.g. – Internet Protocol, Internet Packet Exchange (IPX), Sequenced Packet Exchange (SPX), APPLE TALK.
2. ROUTING PROTOCOLS
This protocol defines how the data packet will converge from one network to another. It defines the best path also known as shortest path to reach destination on network
i. Routing information protocol
ii. Open Shortest Path First
iii. Enchanced Interior Gateway Routing Protocol
iv. Border Gateway Protocol
6. DATA LINK LAYER
This layer is responsible for defining the format for layer two frame as well as the mechanics of how devices communicate with each other over the physical layer. The data link layer is responsible for the following
1. Defining the MAC address or Hardware Address or Physical Address
2. Defining the physical or hardware topology for connection.
3. Defining how the network layer Protocol is encapsulated in the data link layer frame.
4. Providing both connectionless and connection oriented services.
MAC ADDRESS- Media Access Controller mac address is unique physical or hardware address i.e. represented in hexadecimal number. MAC address is 48 bit address every lan port and wifi adapter has its own unique mac addresses .
7. PHYSICAL LAYER
The bottom most layer of OSI model in the physical layer. The physical layer is responsible for the physical mechanics of a network connection, which includes the following
1. The type of interfaced used in networking device
2. The type of cable used in the networking devices.
3. The connector used in each end of the cable.
4. The pin pattern used for each of the connections on the cable.
5. The encoding of the messages on the symbol by converting binary digits to a physical representation based on the media type such as electrical copper, light for fibre and radio for wireless.
Thanx for reading