OSI MODEL

OSI (OPEN SYSTEM INTERCONNECTION)

-It is a reference model

-In actual we use TCP/IP (transimition control protocol / internet protocol)

-It consist of 7 layers

- It is developed by ISO ( International orginasition for standardisition)

PHYSICAL LAYER :-

- Data will be in bits

- Bits will be converted into light signals or electric signals

- protocol data unit is bits  

DATA LINK LAYER :-

-It adds hedder & trailer
-Header & trailer cotains MAC address of source and destination
-Header contains destination MAC address
-Trailer contains source MAC address
-protocol data unit is frame

Network layer :- 

-the routing layer

-It provides addressing and routing service

- There are 2 addresses in packet one is source address & another is destination address

-The primary network protocol on the neternet , IPv4 ,IPv6 logical addressing

-It is used to connect multiple network 

-network layer does not broadcast the data

-protocol data unit is packet

Transport layer :-

-It is responsable to transmite entire message from source to destination by selecting 2 protocol (TCP/UDP)
-protocol data unit is segment

<>TCP (transmition control protocol):- 

1.It is connection oriented 

2. It is relible

3. It is little bit slow in processing

4. It has more pay loads

ex:-HTTP (hyper text transfer protocol) , FTP (file transfer protocol) , SMTP (simple mail transfer protocol)

<>UDP (user data gram protocol):-

1.It is connection less 

2. It is unrelible 

3. It is fast as compared to TCP

4. It has low pay load

ex:-DNS (domain name system) , TFTP (trivial file transfer protocol) , DHCP (dynamic host control protocol)

 

Session layer :-

1. create & manage the session via port no

2. it works as giving authentication like (user name , password)
3.protocol of data unit is data

presentation layer :-

1.used to present the data in correct formate

2. we can assigne security by extention name ( .exe , .com , .in)

3. encoding assigning code

4. encrypting providing security

5. compressed to reduce size of file

6. protocol data unit is data

Application layer :-

1. Appliction of computer runns under application layer

like (yaho, facebook ,messanger)

2. protocol data unit is data