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CCNA Training Course: OSI Model Part 3

Posted: October 21st, 2016

Physical Flow of data When the data arrives at its intended destination it will travel up the 7 layers to pop out onto the Users application as a for example an email or webpage. When the user on the left hand machine press the send button on their email program the email is sent down the stack starting at layer 7 and through the layers. There is no way of avoiding passing through a layer. As the data moves through each layer the functions of the layers will determine exactly what happens to the data. Logical flow of data The...

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CCNA Training Course: OSI Model Part 2

Posted: October 21st, 2016

How Layers are used In a layered system, a layer is considered to be a service provider to the layer above it. The upper layer is considered to be a service user by the lower layer. The service user avails itself of the services of the layer below by sending a transaction to the provider. This transaction informs the provider as to the nature of the service that is to be provided. A layer cannot be by passed, even if the end user does not require the services of that layer, the user must still “pass though” the layer on...

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CCNA Training Course: OSI Model Part 1

Posted: October 21st, 2016

NETWORK MODELS AND PROTOCOLS This next chapter will describe two very important concepts in networking known as protocol stacks. There are two very important protocol stacks which as a network engineer you must know the OSI model and the TCP/IP model. Knowledge of both these models will help you understand the role of various devices that go to make up a network also help you design, configure and fault find a network more efficiently. The OSI model One of the very first concepts I learnt when I entered this networking arena back in the 90’s was that of the “Protocol...

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Part 6: CCNA Training: What is a Network

Posted: October 21st, 2016

CABLING AND TOPOLOGIES Topology: Physical Bus A bus network is a single length of cable to which work Stations, printers, servers, routers etc. connect. There have been two major physical bus technologies: • 10Base5 • 10Base2 • 10Base5   This technology capable of 10Mbps and allowed a cable run of 500m with the maximum number of nodes connected to the wire limited to 100 devices at a distance of 2.5meters apart. 2.5 Meters is due to the wavelength of the signal used to transmit the data. At each end of the cable run there was a terminator (Resistor of 50ohms),...

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Part 5: CCNA Training: What is a Network

Posted: October 21st, 2016

CCNA TRAINING: THE NETWORK INTERFACE CARD AND BIA ADDRESS There are a few ways to connect to a network for this moment we will concentrate on a wired only connection. To connect to a network it is common to use a cable attached to a port on your P.C called an Ethernet port using an RJ45 connector. Every interface has been assigned a unique address called a “Burned in Address” which identifies the interface uniquely on the network. Every Frame which your device sends will include the unique BIA (Burned in Address) as a source address. The BIA The BIA...

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Part 4: CCNA Training: What is a Network

Posted: October 21st, 2016

How Binary Works Imagine this, you and your friend live across the road from each other, at night you wish to communicate using flash lights, you need to have an agreed code of light flashes. So you agree on the following code, to represent a single binary 1 you will switch the light on for one second and to represent a binary zero you will keep the light off for one second. Of course this is going to quickly go to the dogs but you understand the premise that we have agreed on a line code that we both understand,...

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Part 3: CCNA Training: What is a Network

Posted: October 21st, 2016

HOW DEVICES COMMUNICATE When I first started in networking the one thing that I could not get my head around was how does one machine communicate with another?, I understood that P.C’s used binary to communicate but what I could not visualise was how a parcel of data was sent from one interface to another in my mind I used to picture a precession of packets on the wire in line one after the other like in the diagram below. Of course I soon realised that this was not possible, we are talking about a single pair of wires to...

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Part 2: CCNA Training: What is a Network

Posted: October 21st, 2016

Don’t worry too much about all some of the terms like “Frame” for now, simply make a note of them, writing things down helps recollection later on. The biggest draw back of using hubs is that they are not “intelligent” devices. When we speak of intelligence in a piece of networking gear we are referring to the ability to examine the parcel it receives  and determine how to best deliver this parcel of data. A hub will flood all data received out of all ports. Devices receiving data which they know is not for them will dispose of the data....

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Part 1: CCNA Training: What is a network

Posted: October 21st, 2016

Intro to Networking What is a network? How would you answer this? What would you say if you were asked to explain “what is a network” in your job interview? To put it simply a network is a collection of devices that move parcels of information from A to B. Do not think of a network as any more complex than this statement and you will find that networking is a complete doddle, I promise. Of course there will be those who will think that I am trying to down play the sometimes complex nature of networks, sure, yes networks...

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Attack of the Clones

Posted: October 21st, 2016

When I started Commsupport in the famous garden shed at the end of my garden on that cold January in 2007 many people used to call and ask how I could offer courses at such low prices when every other training company was charging thousands for the same course, well since that fateful January I have proved that a great course can be delivered despite the low cost much to the distress of my competitors. With almost 4000 students having attended our courses, we have proved that I and my gang of elves at Commsupport have built a company which...

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