Online storage (オンラインストレージ) is a service where you rent, over the internet, storage space that a provider has set up on its servers, and keep your files there.
Your files move from a local storage device to the far side of the network, so every read and write goes through a connection. Because they are kept apart from your devices, a broken or lost device is unlikely to cost you the files you stored.
AnalogyThink of storing your things in a rental locker in town instead of a closet at home. With the key, you can collect the same items from any station.
How to rememberThe Japanese ストレージ is simply the English word storage (a warehouse or repository) written in katakana, so the whole term reads as "a warehouse online."
Exam points
ExamHow much you can store depends on the allowance the service gives you. Adding auxiliary storage (補助記憶装置) to your device does not raise it.
ExamWhat you rent is storage space for your files. That is a different thing from a VPN, a virtual private network built across the internet.
IP telephony (IP電話) is a phone service that converts voice into data and exchanges it over an IP network, a network that carries data using the IP communication protocol.
Turn voice into data
Split into small chunks
Carry over the IP network
Turn back into voice
The other party's side turns the data back into voice.
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The internet is one kind of IP network. The technology that turns voice into packets (small chunks of data) and sends and receives them in real time is called VoIP.
AnalogyInstead of chartering a private train for your voice, you put it on a shared bus that also carries other passengers and their luggage.
How to rememberVoIP stands for Voice over IP. Read over as "riding on," and you get voice riding on IP.
Exam points
ExamIP telephony (IP電話) does not have to run on the internet; a closed IP network inside an organization also works. It can also place calls to the ordinary telephone network.
ExamVoIP is not limited to telephone services; it is used for voice calls over the internet in general.
Mix-upThe technology that turns voice into packets (パケット) is VoIP. IP-VPN is a way to secure communication between sites and has nothing to do with converting voice.
A line carrier (回線事業者) is an operator that sets up and supplies communication line facilities such as optical fiber, telephone lines, and base stations.
The line between a telephone office (the local exchange, 収容局) and a subscriber's home is called the subscriber line (加入者線), and what the line carrier uses for it shapes the character of the service. For example, ADSL runs high-speed digital communication over existing metal (copper) phone lines, while FTTH replaces that line with optical fiber. High-speed lines like these are collectively called broadband lines (ブロードバンド回線).
AnalogyIt resembles a company that builds and maintains roads. Whatever vehicles travel and whatever they carry is a separate matter; it supplies the road itself.
How to rememberIts other name, carrier (キャリア), literally means "something that carries," which ties it to the companies that own the paths data travels on.
Exam points
ExamADSL runs over metal (メタル) telephone lines.
ExamADSL is faster downstream (下り, receiving) than upstream (上り, sending). The farther you are from the exchange, the lower the speed.
ExamBroadband lines (ブロードバンド回線) suit large data exchanges such as video streaming and also support always-on connections (常時接続).
An ISP is an operator that gives users access to the internet, and is also called a provider (プロバイダ).
A user's traffic passes through the ISP's network on its way out to the internet. Many ISPs also do things like issue email addresses along with the connection. A single company may act as both a line carrier and an ISP.
AnalogyIt resembles the interchange where a local road joins the expressway. Only by passing through it can you enter the main route toward distant destinations.
How to rememberISP stands for Internet Service Provider. The Japanese alternate name プロバイダ is just the last word, Provider, written in katakana.
Exam points
Mix-upAn ISP handles the connection to the internet, while an ASP (application service provider) provides applications over the network.
An MVNO (mobile virtual network operator, 仮想移動体通信事業者) is an operator that rents another company's mobile network and sells mobile service under its own brand.
Network owner (MNO)
Network renter (MVNO)
User (contracts with the MVNO)
An operator that owns its mobile network is called an MNO, and an MVNO uses that network. Because it keeps investment in base stations and similar equipment down, many MVNOs offer low-priced plans known as budget SIMs (格安 SIM).
AnalogyPicture a travel agency with no vehicles of its own that rents seats on a major bus company's routes and sells tours under its own name.
How to rememberLook at the Virtual in Mobile Virtual Network Operator. The V is your signal that the company does not actually own a network.
Exam points
ExamAn MVNO does not allocate radio frequencies (周波数); it sells communication services to users. It is also distinct from the support companies that back MVNOs behind the scenes.
Mix-upMNP is the system for switching carriers while keeping your phone number, whereas MVNO names a type of operator.
Packet communication (パケット通信) is a method that splits data into small chunks called packets (パケット) and sends them chunk by chunk.
Data to send
Split and add headers
Forward over a shared network
Reassemble at the receiver
The header information lets the receiver put the arriving chunks in order and restore the original data.
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No single communication monopolizes a path; many share the same one, so the line is used efficiently. This way of sending is called packet switching (パケット交換方式), and internet communication works this way.
AnalogyIt is like packing for a move in numbered boxes, sending them by a courier that mixes them with other people's parcels, and opening them in number order at the new place.
How to rememberPacket means a small parcel: pack plus -et, a suffix that signals smallness.
Exam points
ExamData usage is calculated from the number and size of the packets (パケット) exchanged.
Mix-upCircuit switching (回線交換方式) holds a path for itself, which makes speed easier to guarantee, while packet switching (パケット交換方式) shares the path. Large data can still be sent by dividing it into many packets.
Optical communication (光通信) is a method that converts electrical signals into light and sends it through optical fiber (光ファイバ).
ADSL
FTTH
Subscriber line medium
Metal telephone line
Optical fiber
Signal carried
Electrical signal
Light signal
Optical fiber is a thin strand made of glass or similar material. Signals weaken less in it than in copper wire and electrical noise affects it less, so it suits high-speed, high-capacity transmission.
AnalogyInstead of shouting to someone far away, imagine signaling with a flashlight. Light reaches a long way, and faster flashes carry more information.
How to rememberFTTH stands for Fiber To The Home. Fiber here is the same word as the ファイバ in 光ファイバ.
Exam points
ExamFTTH is an access service that runs optical fiber (光ファイバ) from the exchange all the way into an ordinary home.
Online storage moves where data is kept to the far side of the network; IP telephony moves the path voice travels onto an IP network.
An ISP's connection service runs on top of lines supplied by a line carrier.
An MVNO has no network of its own, and renting one makes low-priced plans easier to offer.
Packet communication concerns how data is divided and optical communication concerns the medium that carries the signal, so one communication can use both.