Other networking Applications
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Key Types:
- User Services:
- Messaging (e.g., WhatsApp)
- Video Conferencing (e.g., Zoom, Teams)
- Remote Login (e.g., SSH, AnyDesk, TeamViewer)
- Utility Services:
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DNS (Domain Name System): Translates human-friendly domain names (e.g., google.com) into IP addresses that computers use to identify each other.
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NTP (Network Time Protocol): Synchronizes the time across computers and devices over a network to ensure accurate timestamps.
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PTP (Precision Time Protocol): Provides very precise time synchronization for networks, often used in environments where microsecond-level accuracy is needed, like industrial or telecom applications.
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- User Services:
Data Communication
Network applications transfer data from senders to receivers through a medium, following rules defined by communication protocols.
Data Representation
- Text: Represented using character encoding schemes (e.g., ASCII, Unicode).
- Numbers: Stored as binary values.
- Images: Made up of pixels, each represented by a bit pattern.
- Audio: Converted from analog to digital using encoding techniques.
- Video: Also encoded into bit patterns for transmission.
Text and Numbers
- Encoding: Text and numbers are converted into binary values.
- ASCII: A common encoding scheme that uses 1 byte (8 bits) per character.
- Unicode: A more extensive encoding scheme that uses 4 bytes per character.
Images
- Pixels: Images are made up of small picture elements called pixels.
- Pixels are represented in form of bits
- Resolution: The number of pixels in an image (e.g., 1024x768) determines its resolution.
- High Resolution: More pixels, sharper and more detailed images.
| Factors | Low Resolution | High Resolution |
|---|---|---|
| Image Quality | Poor, blurry, pixelated | Clear, sharp, high definition |
| File Size | Small | Large |
| Color Accuracy | Limited color range | Wide color range, accurate colors |
| Printing Quality | Not suitable for printing | Suitable for large format printing |
| Detail | Low detail, visible pixels | High detail, smooth edges |
| Video Quality | Grainy, low-quality | Crisp, high-quality |
| Storage Capacity | Can store more images | Can store fewer images |
| Display Devices | Suitable for smaller screens | Suitable for larger screens |
| Viewing Experience | Unpleasant, hard to view | Pleasant, easy to view |
| Cost | Inexpensive | Expensive |
Audio and Video
- Audio: Analog sound waves are converted into digital audio using encoding techniques like Advanced Audio Coding (AAC).
- Video: Similar to audio, video data is encoded for digital transmission.
Data into Signals
- Data Conversion: Data is converted into binary values, then to voltages to be transmitted.
- Voltage Levels: A high voltage (e.g., 2.0 volts or above) represents a binary “1.” A low voltage (e.g., 0.8 volts or less) represents a binary “0.”
Data > Encoded Values > Binary Values > Voltages
Transmission of Data
Computer networks are designed to transfer data from one point to another
- Transmission Modes:
- Wired Transmission: Using physical cables.
- Wireless Transmission: Using electromagnetic waves (without cables).
- Mode is selected according to the several factors (Cost / Speed/ Accessibility/Feasibility)
- Signal Type: Wireless data transmission uses electromagnetic (EM) waves.
Characteristics of Electromagnetic Waves
- EM waves doesn’t require any medium material medium to travel
- Medium: Can travel through air, solids, and vacuum.
- Speed: Constant in a vacuum (3 x 10^8 m/s-1)300,000 kmps - Speed of light
- Spectrum: EM waves exist across a wide spectrum, used for different purposes. (light is also a EM wave)
Signals
- Analog Signals: Have continuously varying values.has infinitely many levels of intensity over a period of time.
- Digital Signals: Have a limited number of discrete values (usually 0 and 1).
- Periodic Signals: Repeat themselves after a fixed time.
- Non-Periodic Signals: Do not repeat themselves regularly.
NOTE
In data communication, we commonly use periodic analog signals and non-periodic digital signals
| Difference Between Analog And Digital Signal | Analog Signals | Digital Signals |
|---|---|---|
| Type | Continuous signals | Discrete signals |
| Representation | Represented by sine waves | Represented by square waves |
| Examples | Human voice, natural sound, analog electronic devices are a few examples | Computers, optical drives, and other electronic devices |
| Value Range | Continuous range of values | Discontinuous values |
| Recording | Records sound waves as they are | Converts into a binary waveform |
| Usage | Only used in analog devices | Suited for digital electronics like computers, mobiles and more. |
Characteristics of a Wave
- Amplitude: The height of the wave.
- Frequency: The number of cycles per second (Hertz - Hz).
- Wavelength: The distance between two consecutive crests (or troughs) of a wave.
- Period: The time it takes for a wave to complete one cycle.
- Speed: The distance a wave travels in one second.
Period and Frequency
- Period: How long one cycle takes.
- Frequency: How many cycles occur in one second.
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- Period: The time it takes for the wave to complete one cycle (from crest to crest or trough to trough). The period is marked as 1/12 seconds.
- Frequency: The number of cycles completed by the wave in one second. The diagram shows 12 cycles within 1 second, so the frequency is 12 Hz.
Relationship
Frequency and period are inversely proportional:
- Frequency = 1 / Period
- Period = 1 / Frequency
If a signal generator generates a signal which has 30000 cycles per minute.What is the frequency of this signal? What is the period of the signal?
Number of cycles per minute = 30000 Number of cycles per second = 30000/60 = 500 Frequency = number of cycles per second = 500 Hz Period of the signal = 1/f = 1/500 s = 0.002 s = 2ms
Wavelength (λ)
- The distance between two consecutive crests or troughs of a wave.
Wavelength (λ) and Speed
- Relationship: Speed (V), wavelength (λ), and frequency (f) are related by the formula:
V = λ * f.
- Wavelength = Velocity / Frequency
- Frequency = Velocity / Wavelength
Data Flow Models
- Simplex Mode: Unidirectional, only one device can transmit at a time.
- Tv, Radio
- Half Duplex Mode: Both devices can transmit and receive but not at the same time. ONE AT A TIME
- Walkie-talkie
- Full Duplex Mode: Both devices can transmit and receive simultaneously.
- Any device used in computer networks
Summary >>>
- Data is converted to binary and then to electrical signals for transmission.
- Signals are transmitted over networks using different media and modes.
- Signals have characteristics like frequency, wavelength, and velocity.
- Electromagnetic waves are used for wireless data transmission.