What is Ethernet – CSMA /CD – Introduction to OSI layer model – The internetworking Part3

What is Ethernet – CSMA /CD – Introduction to OSI layer model – The internetworking Part3

If I go by history Ethernet was developed by XEROX to communicate between printer and a PC I might be wrong but I read it somewhere on the internet. Basically Ethernet is technology to connect various devices which are in close proximity .The devices could be printer, faxes, servers ,pc etc . All of these devices can be connected to a single link using Ethernet .which is a very good idea and its is light on the pocket too . The length of the Ethernet links are limited to few 100 meters only . So it is used to connect only local devices or devices that are few 100 meters apart .The main problem that arose while using Ethernet was collisions. The devices where sharing the same link so they were transferring data at the same time and frames were colliding so a technique called CSMA/CD (Career Sense Multiple Access with Collision Detection )was introduced .
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Intro To Transport layer – Introduction To OSI Layer Model – The Internetworking Part2

Intro to transport layer – Introduction to OSI layer model – The internetworking Part2

The transport layer deals with segmentation and reassembly . 2 protocols work on this layer TCP and UDP. TCP(Transmission control protocol) being the connection oriented and UDP(user datagram protocol) being connectionless.

I will get to UDP later on .Now talking about TCP. It is said to be connection oriented protocol .TCP employs sequencing, acknowledgments and retransmission . If the data is not reached in order at the receiver it has to be retransmitted .

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Introduction To OSI Layer Model – The Internetworking Tutorial Part1

Introduction to OSI layer model – The inter networking.

Why we need a model for inter networking . If a model has a flaw why cant we just change the model according to our needs and then use it . This is what WE do while coding but this is not in case of networking.

Imagine you being an English reader and I am writing this article in French. Will you be able to understand it . Probably not .This is the same case with networks they need to work on the same architecture through.

In the earlier days of internet there was no defined model for networking which was a pain in the neck (I wanted to use something else in place of neck but :) ) So OSI (Open System Interconnect came up with A layered approach .Which was consistent for all and it divided the network architecture into 7 layers .Why we needed a division . Hmmm consider a post office . The post office is divided into several departments one receives the parcel and add some info to it . The next department parses the parcel based on the info from previous department and send it to the higher department. If the parcel reaches directly to second department it cannot process as it needs some information which can only be present if it comes visa department1. All the work can be done by a single department also but it will lead to a disastrous situation. It is just like a man who is working as a peon , clerk, manager accountant etc a one man army example

Similarly this division was necessary for networking . The 7 layers were Application, Presentation, Session, Transport, Network, Data Link, and Physical . CHEAT SHEET( Please Do Not Take Sausage Pizza Away ) .The first letter of each word is the starting character of a layers name but in opposite order .Each OSI Layerprovide services to the layer above it and receives service from the layer below it.Same as I mentioned in the above example.

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Setting Up Of A Cisco Home Lab

Hello readers this question goes through mind of everyone who is appearing or wants to appear for any of the  cisco

certification …. Now question comes that can everything be practiced on Simulators … hmmm

quite a big question but the answer is not . Simulators are very good way to start your path towards cisco but in the end to

gain real knowledge you need to have hands on some hardware . It is not possible for everyone to get a router though they are cheap on ebay but still costs some money which everyone can’t afford .

The initial ccna exam can be cleared almost without purchasing any real hardware but if you want to make your career into cisco you need to have hands on some hardware .

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