(new) CS2 - Data transmission

What are packets?

Small units of data

What are sections of a data packet?

Packet header

Payload – actual data that is broken into small units to be sent in packets

Trailer – mark the end of a packet and store error detection systems

What are Inside the packet header?

Destination address – IP address

Packet number – put the package back in order to re-create the file

Originators address – IP address of the center to trace where Datta came from in case of illegal activities or requests to resend

What is packet switching?

Transmitting packets where each packet is sent individually across different pathways in a network

What is a router?

Controls the pathway used to transmit each packet

How does packet switching work?

• Packets are sent through different pathways

• When packets reach a router, it decides the next pathway to sent it along

• This continues until all of the packets reach the receiver

• The packets are reordered to recreate the file

What is seal data transmission?

Each bit of data is transmitted one at a time using a single wire

What advantages of serial data transmission?

Data arrives in or so it doesn’t get skewed

A single wire lest chance of interference meaning less chance of error

Only one wire so cheaper to manufacture and make

What are disadvantages of serial data transmissions?

Datta transmission is slower as it is one bit at a time

More data may be needed to indicate when transmission starts and stops

When is serial data transmission used?

Transmissions over longer distances

What is parallel data transmission

Multiple bits of data are sent at the same time through each wire

When is parallel transmission used?

Over shorter distances

What is simplex data transmission?

Data is transmitted from across devices in One Direction

when is simplex data transmission used

When there is no need to send Datta through the other direction

What is half duplex Datta transmission

Data is transmitted through both directions, but One Direction at a time

When is half duplex Datta transmissions used

To transmit data through both directions, but it isn’t sent at the same time.

It can also be used when needing a high-level performance and communication but as different channels are used.

What is full duplex Datta transmissions

Data is transmitted in both directions at the same time

What are USB devices?

A USB interface is used to plug a USB port and uses USB connection to transmit data

What type of data transmission does USB use?

Serial data transmission however it is especially designed to transmit data faster

What advantages of USB?

A simple interface allows it to be inserted only in one way reducing chances of error

The speed is fast. Data is transmitted quickly.

USB port is in many devices

Automatically detect when inserted you may need to download drivers in the first input, but after that, there’s no need to download

Can be used to power device

What are disadvantages of USB?

The length of USB cable is limited

It is not as fast as ethernet

What can happen to data from interference?

It could be lost gained or changed

What are error detection methods?

Parity check

Check sum

Echo check

ARQ

Check digit

How does parity check work?

Each bite has seven bits and one extra bit called a parity bit

Before transmission, the parity is checked and said to either even or odd

The number of ones in the seven bits is counted and totaled

If parity odd is used and the number of ones is odd, the parity bit would be zero if the number of ones is even the parity bit would be set to one so in total the number of ones is odd

Even Parity is used and the number of ones is even the Pari bit is sent to zero otherwise, if the number of one bits are odd, the parity bit is set to one so in total the number of ones are even

How does checks work?

A method is used to calculate a value from the data

This value is added to the data transmitted

The receiver uses the same method to calculate a value from the data

If the values match, there has been no error

If the values do not match, there has been an error

How does echo check work?

The send transmits data to the receiver

Receiver, transmit data back to the sender

The sender compares data. It has received to check if it matches.

If it does, then there is no error

If it does not then there has been an error

How does automatic repeat request work for positive acknowledgment?

Send send the first data packet

Receiver receives the data and checks for errors

If no errors acknowledgment is sent

The sender receives the acknowledgment and knows there are no errors so data packet is sent

If the sender does not receive an acknowledgment in the time limit timeout occurs

Resent the data when timeout occurs until acknowledgment happens

How does ARQ work for negative acknowledgment

Send send first data packet

Receiver gets data packet and checks for errors

If there are no errors, nothing else happens

If there is an error, a negative acknowledgment is sent by the receiver

When the center receives the acknowledgment it resets the data packet

A time limit is set so if time runs out and no acknowledgment is received the sender knows that there are no errors and and since the next Datta packet

What is check digit used for

Check digit is used to check data during data entry, whether manual or automatic

How does check digit work?

A value is calculated from the data and stored with the data

When data is entered, the digit is recalculated from the data

If the previous value and the calculated value match the data is correct

If the previous value and the calculated value do not match, the data is wrong

What does plain text mean?

Data before encryption

What does encryption key mean?

Encryption algorithm that is used to scramble the data

What does ciphertext mean?

Encrypted data

Why is encryption used?

To make the data meaningless to hackers as they don’t understand it

How does General encryption work?

Data before Encryption is plain text

Plane text goes through an encryption, algorithm or key

The encryption key turns the text into cyber text

Cypher text Transmitted from one device to another

How does symmetric encryption work?

Plane text encrypted into ciphertext with an encryption key

Cipher text and encryption key are sent separately to receiver

The same key is used to decrypt the file

What is the metric encryption used for?

To encrypt data that is not sent across the network

How does asymmetric encryption work?

Please text is encrypted into cyber text using a public key, which is an encryption algorithm

cipher text is Transmitted to receiver

Cyte is decrypted using a private key. It cannot be decrypted using a public key.

What is a public key?

It is a key that anyone can see

What is a private key?

A key that is kept private