Networks: from local to global

Содержание и основные понятия

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Alterna · Chapter 4 · page 4.1
Networks: from local to global
One computer is an island. Two computers connected by cable are already a bridge. A billion computers connected to wires, radio waves and satellites are the Internet. This page shows how the networks work, from the school computer class to the global web.
In chapter 3, you saw that there was an operating system.
Network Walls
What does it take for your laptop to open a website with a server on another continent?
Answer —
Computer network
:A set of devices and channels of communication that allow data to be exchanged. Networks range from tiny (two phones on Bluetooth) to giant (an Internet that connects billions of devices). This is where you can figure out what networks exist, how they are built and what equipment connects them.
GEF · Basic
PIF · Baseline
01
What is a computer network?
Why computers connect together online and what tasks that solves.
GEF
Definition
Computer network
- It's two or more computers (or other devices) connected to communication channels and working according to common rules (protocols) to share data and share resources.
Why do you need nets?
Data exchange
- sending files, text messages, video calls.
Total access to resources
- One printer for the whole office, a shared Internet channel, a network vault.
Joint work
- A few people can simultaneously edit a document in a cloud.
Access to information
World Wide Web (WWW), e-mail, databases.
Relationship to Chapter 3
You've seen it in the "film system" section.
Internet route
—
\\server\share\file.txt
It's a call to a file on another computer on the network, and networks make these ways possible.
What's on the network?
Any network consists of three elements:
Hinges
- devices that send, receive or transmit data (computers, telephones, servers, routers).
Channels of communication
- Wi-Fi, Bluetooth, cell phone connections.
Protocols
For example, the IP protocol is responsible for addresses and TCP for reliable delivery.
02
Types of networks: from personal to global
Networks are classified by size, ranging from a pair of devices to planetary infrastructure.
GEF
Classification by coverage
Type
Decrypting
Size
Example
PAN
Personal Area Network
Up to 10 m
Phone + Bluetooth earphones
LAN
Local Area Network
Building, floor
Network at school or office
MAN
Metropolitan Area Network
City
Bank network with branches in the city
WAN
Wide Area Network
Country, continent
Corporate network between countries
Internet
Global Network
World
World Network Network
📱
PAN — Personal Network
An analogy: conversation in whisper
Bluetooth headphones, smart watches, transmission of photos between phones, short distance, low speed, minimum energy.
🏫
LAN Local Network
analogy: conversation in class
Computers in one building exchange data at high speed, a common printer, a file server, an Internet via one channel.
🌐
Internet Network
Analog: World mail
Millions of LANs and WANs are connected. Data pass through dozens of intermediate nodes before reaching the target.
Important
Wi-Fi is not a kind of network, but a wireless connection. Wi-fi can be used in PAN (telephone-roller), LAN (home network) and even in MAN (urban hotspots).
🌍
Identify network type
10 scenarios PAN, LAN, MAN, WAN or Internet
Interactor
Read the description and choose which type of network is best suited.
03
Network topology
As devices are physically connected: star, ring, tyre, and honeycomb structure.
GEF
PIF
What is topology?
Network Topology
It's a pattern of connecting nodes, and topology determines the reliability, the speed and the cost of the network.
Four basic topologys
🔍
Topology explorer
Press the topology · study the pros, cons and real examples
Interactor
Choose the topology of the network to learn about its features: how it works, where it applies, what its strengths and weaknesses are, and look at real examples of use.
HUB
SHORTS
Central Node
All devices are connected to one central device (mistor or concentrater).
Easy diagnostics
♪ One cable isn't affecting the others
♪ If the center breaks down, the whole network falls ♪
♪ Needs more cables
Where used:
Domestic Wi-Fi networks, office LAN, school computer classes
04
Network equipment
What devices connect computers to the network and send data.
GEF
Basic devices
Device
What he does
Analogies
Rooter's home.
The home Wi-Fi router is actually three devices in the same housing:
router
(connects the home network with the Internet)
Switch
(for wired devices) and
Access point
(for Wi-Fi).
🔌
Gather the network.
Pull the devices together
Interactor
Press the device, then press the desired function or drag it. Each device performs its function. Devices change at each load!
Devices
Functions
05
Internet Network
Like millions of local networks, they connect to a global network.
GEF
What is the Internet?
Internet
It is a global network of millions of private networks (LAN, WAN, corporate networks) around the world; no organization owns the entire Internet; it consists of many independent networks that have agreed to share data.
Map of global networks
Under the oceans are transoceanic cables connecting continents, and this is what a simplified map of the main Internet backbone channels looks like:
C. America
U. America
Europe
Asia
Africa
Australia
NYC
LON
TKY
SYD
SAO
MOW
Figure 1.
Simplified map of Internet backbones. Parameter lines are submarine cables. Points are major traffic points (IXP): NYC (New York), LON (London), TKY (Tokyo), SYD (Sydney), SAO (São Paulo), MOW (Moscow)
How do the nets connect?
Supporters (ISP)
The home router connects to the provider and the provider to the larger networks.
Main channels
- powerful fibre-optic lines connecting continents and countries.
Exchange points (IXP)
- places where providers exchange traffic directly.
Fact
Under the oceans are transoceanic cables with a thickness of garden hose that transmit data between continents at the speed of light. Satellite Internet is only for remote areas where there are no cables.
The principle of package switching
When you send a file or open a website, the data doesn't fly in one piece.
Packages
Each package travels on its own and can come in different ways. At destination, the bags are collected back in the right order.
It's like sending a book not by one package, but by taking it into chapters and sending it to each chapter separately. If one chapter gets lost, they'll ask you to send it only, not the whole book.
06
IP addresses: How computers find each other
Every device on the network has a unique address, like a postcode for data.
GEF
PIF
What's an IP address?
IP address
Internet Protocol adress is a unique numerical identifier of a device on the network. Without it, the data would not know where to go.
IPv4 – Classical format
It consists of four numbers from 0 to 255 divided by points:
192.168.1.105
Each number is 8 bits (one byte), only 32 bits, which gives about 4.3 billion possible addresses.
Why do the addresses end?
4.3 bill