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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, now it’s simply a matter of keeping count of the on’s and offs to interpret the code as one and zeros to reconstruct the message.

When one P.C wishes to communicate with another P.C is will tap out on the wire using electrical pulses a series of binary bits, sequences of these binary bits represent letters, numbers and other characters, the most commonly used character coding is known as ASCII. Most modern character-encoding schemes are based on ASCII (American Standard Code for Information Interchange). Codes represent text in computers, communications equipment, and other devices that use text. Most modern character-encoding schemes are based on ASCII, though they support many additional characters.

The letter A is = 1000001

The letter F is = 100 0110

The letter W is = 101 0111

The % is = 010 0101

Can you decode the following message?

NOTE: To convert drop the first binary character using the ASCII encoding

01101001 00100000 01100001 01101101 00100000 01100001 00100000 01100010 01101001 01101110 01100001 01110010 01111001 00100000 01100111 01100101 01100101 01101011

When a P.C communicates with another P.C on the network it will create a parcel of data called a frame, this parcel of data is a up to 1500 bytes in size, a byte Is another way to state 8 bits or an octet, so a byte is an octet and octet is 8 bits. Therefore 1500 byte is 1500 x 8 = 12000 bits per frame of data.

Each frame your P.C creates has the following fields.

  1. Destination Address
  2. Source Address
  3. Length
  4. Data
  5. Frame Check sequence

Data Frame Example

 

figure-9

The frame is pretty much like any parcel which you would send in the post, it has an address where we would like the parcel to be sent to, the address of the interface which transmitted the frame since data communications is generally a bi-directional operation.

The frame also has dimension just like a parcel in the way of length and type of data it is carrying