【Lecture9】Computer Systems & Networks
Computer Systems & Networks
What is a mesh network?
Google Nest Wifi and Google Wifi are mesh network Wi-Fi systems. A mesh network is a group of devices that act as a single Wi-Fi network; so there are multiple sources of Wi-Fi around your house, instead of just a single router. These additional Wi-Fi sources are called points.
Since Google Nest Wifi and Google Wifi are broadcasted from each point around your house (and not just a single router), they can provide better coverage over a wider space. If you have a large house, you can add more points for additional Wi-Fi coverage.
All points are connected to each other wirelessly. As long as they are within range, they can communicate with one another wirelessly without the need for a router or switch. This allows for fast and efficient data routing.
What is the NBN?
The nbn is Australia’s national broadband network. It’s replacing copper wires and cable broadband with optical fibre and other technologies to deliver more reliable, high-capacity internet to your home.
What is Transmission Media?
The transmission media can be defined as a pathway that can transmit information from a sender to a receiver.
Transmission media are located below the physical layer and are controlled by the physical layer. Transmission media are also called communication channels.
2 Types of Transmission Media
- Guided Media
- Unguided Media
Guided Media
It is also referred to as Wired or Bounded transmission media. Signals being transmitted are directed and confined in a narrow pathway by using physical links.
Features
- High Speed
- Secure
- Used for comparatively shorter distances
3 major types
- Twisted Pair Cable
- Coaxial Cable
- Optical Fiber Cable
Unguided Media
It is also referred to as Wireless or Unbounded transmission media. No physical medium is required for the transmission of electromagnetic signals.
Features
- The signal is broadcasted through air
- Less Secure
- Used for larger distances
3 major types
- Radio waves (AM and FM radios and cordless phones use Radio waves for transmission)
- Microwaves (majorly used for mobile phone communication and television distribution)
- Infrared (Such as TV remote, wireless mouse)
ADSL (Asymmetric Digital Subscriber Line)
Modulation and Demodulation
Crosstalk and Right Hand Rule
Crosstalk is a disturbance caused by the electric or magnetic fields of one telecommunication signal affecting a signal in an adjacent circuit.
Twisted pair Ethernet Cable reduces that magnetic field. (Placing the wires next to one another will greatly reduce the energy of the magnetic fields created by each wire.)
FTTP, FTTN, FTTC
FTTP (Fiber to the Premises)
- 光ファイバーを利用した高速データ通信サービスのうち、光ケーブルを利用者の元まで直接引き込む導入形態の総称
- FTTP offers typical download speed plans ranging from 12 Mbps up to 1,000 Mbps (1Gbps).
- FTTP works the same way, only instead of using slow copper cables from the cabinet to your home, it uses fibre cables instead.
FTTC (Fibre to the Cabinet)
Cite: apc
Slower than FTTP but cheaper than that. FTTC uses fibre cables to deliver the internet to your local street cabinet, but after that it uses slow copper cables to reach your home.
FTTN (Fibre to the Node)
Slowest and cheapest but most common since it’s the best for personal use. (The things which most the people use at home are this)
Find the location of IP Address
This website: https://www.iplocation.net/
Microwave
- microwave signals are sent through the atmosphere and space
- expensive
- high frequency radio
- requires direct line of sight
- range of 30 – 70 miles due to curvature of the earth
Satellite
- a communications satellite is basically a microwave relay station in orbit
- range is longer since curvature of earth not an issue (only atmospheric noise & background radiation)
netstat (command)
netstatThe netstat command shows active network connections and displays information about them.