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OSI Layer in a nutshell

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I know for anybody starting from Beginner to Expert in Networking knows what OSI model. But this tutorial is for freshers or those who are new to networking world. Why I am putting OSI in such simple and compact manner is because it enables you to know more things in less time.

7 Layers of OSI reference model

1) Application Layer
2) Presentation Layer
3) Session Layer
4) Transport Layer
5) Network Layer
6) Data link Layer
7) Physical Layer

Features of OSI layer 1 or 2 sentences

1) Application Layer ::
Provides services to the user application. Acts as an interface between the user and application. Some of the functions are identifying communication partners, determining resource availability, and synchronizing communication.
Few protocols that working in this layer ::  HTTP, FTP, DHCP, DNS

2) Presentation Layer ::
Provides independence from data representation (e.g., encryption) by translating between application and network formats. In short it generifies data.
Few protocols that working in this layer ::  SSL, MIME

3) Session Layer ::
Establishes, manages and terminate virtual connection between the applications on systems at both end. Keeps the logical sessions separate.
Few protocols that working in this layer ::  NetBIOS, L2TP, PPTP

4) Transport Layer ::
This layer takes care of the transfer of data like whether the communication to be reliable or not.
Controls the reliability of a given link through flow control, segmentation/desegmentation, and error control.
Few protocols that working in this layer ::  TCP, UDP  

5) Network Layer ::
Provide logical addressing (IP Addressing). Responsible for finding the router and performs the network routing function.
Few protocols that working in this layer ::  IP, Ipsec, ICMP

6) Datalink Layer ::
This layer deals with error correction. Any error encoding that has occurred and might occur in the physical layer are corrected here.
Few protocols that working in this layer ::  ARP, PPP, HDLC

7) Physical Layer ::
Controls transmission of raw bits over the transmission medium. This layer defines the relationship between the device and the transmission medium.
Few protocols that working in this layer ::  DSL, USB, Bluetooth

Note : As the topic has been presented in nutshell. Might not have covered all the points in detail.
 OSI Layer
3
Author:Kirthy2010
4 Comments
LVL 38

Expert Comment

by:younghv
Thank you for posting this. I think I have seen it referenced on every Certification Exam I have taken. Anyone planning to take any IT related exams should commit this to memory.

I can still remember my instructor's trick for remembering the names of the layers:
Please
Don't
Never
Throw
Sausage
Pizza
Away

Yes vote above.
0
LVL 8

Expert Comment

by:sandipkharde
I had remembered by remembering those words... APSTNDB.
0
LVL 3

Expert Comment

by:Karthikeyan Ganesan
Princess
Diana
Not
To
See
Prince
Albert

:-)

Thanks,
Karthik
0
LVL 1

Expert Comment

by:fmha
You remind me thoes old days.

Thanks for refreshing my memory.
0

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