Glossary of terms

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2.4 GHz and 5 GHz

The two bands home Wi-Fi broadcasts on. The lower band gets further through walls but tends to be crowded by the neighbours; the higher one is faster and cleaner at the cost of shorter range. Most of today's routers broadcast both at once.

4G

The fourth generation of mobile network, technically LTE, which gives tens of Mb/s and also carries home connections through a modem with a SIM card.

5G

The fifth generation of mobile network, faster than 4G and with lower latency. The label 5G Ready on a device means it will handle a 5G network as soon as one is available in the area.

802.11

The standard Wi-Fi runs on. The letters after the number (802.11n, ac, ax) tell you the generation: the newer it is, the higher the speed and the better the network copes where there is interference.

A

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ADSL

An older connection over the telephone line where downloading is markedly faster than uploading; that is why it is called asymmetric. Today it is being replaced by VDSL, fibre or a connection over the air.

Aggregation

The ratio in which one line is shared between several customers. An aggregation of 1:20 means that in the worst case twenty connections share the capacity, and a lower number keeps the speed steadier even at peak times.

Activation

Bringing the connection into service: setting up the service on the provider's side and connecting the equipment at the customer's, which with us is usually followed by handing over a router or a modem.

Algorithm

This is an exact procedure or set of instructions used to solve a problem or carry out a particular task. In the context of the internet, algorithms are often used for example to rank search results or to recommend content.

Antenna

It receives and transmits a radio signal. With a connection over the air it is mounted on the roof or the façade and aimed at the provider's transmitter, and the quality of the link stands or falls with a clear line of sight.

API (Application Programming Interface)

An interface that allows two software applications to communicate with each other. On the internet an API is used for example to transfer data between websites and applications.

B

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Backbone

The backbone network that carries traffic between providers and data centres. A home connection is an end branch that joins it somewhere.

Bandwidth

Bandwidth, that is the maximum amount of data a line will carry per second. It is a figure about capacity; how quickly a server answers you is told by latency.

Bit and byte

Connection speed is given in bits per second (Mb/s), file sizes in bytes (MB). One byte is eight bits, so a 100 Mb/s line downloads roughly 12.5 MB per second.

Buffering

Loading video ahead into a buffer so that playback does not stall. When the spinner turns, the player has run out of buffer and is waiting for data.

C

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CGNAT

Sharing a single public address between several customers. It does not get in the way of ordinary browsing, but nobody can reach such a connection from outside. Anyone who needs to connect home to cameras or to storage must have a public IP address.

Cloud

Data and programs stored on remote servers instead of on your own computer. They are reached over the internet, so even a weaker laptop manages what it could not handle on its own.

Cookie

A small file a site stores in the browser so that it recognises you next time. It keeps you logged in or holds the contents of your basket, but it is also used to measure visits.

D

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Data cap

The volume of data you may transfer in a month; once it is used up the speed drops. With fixed connections it is no longer used today, with mobile plans it is.

DHCP

A service that automatically assigns an IP address to devices on the network, so a laptop only needs to be connected to the Wi-Fi and nothing is set up by hand.

DNS

A translator of names into addresses: you type prazskynet.cz and DNS finds out which server the site sits on. Its failure looks like an internet outage, even though the line is running.

DOCSIS

The standard for internet over television coaxial cable, that is over cable television wiring.

Domain

The name of a website, for example prazskynet.cz. It is registered for a year or more and has nothing to do with where the site runs.

Download

Downloading data from the internet to you, the first number in the fraction of a plan. With the 50/5 plan it is 50 Mb/s.

Dual band

A router that broadcasts on two bands at once (2.4 and 5 GHz) and the device picks the more suitable one itself according to distance and interference.

E

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EPG

The electronic programme guide, that is the TV listings right in the television, from which you launch catch-up and the recording of programmes.

eSIM

A SIM card built into the phone that cannot be taken out. It is activated by scanning a QR code and there is no waiting for a plastic card to arrive.

Ethernet

A cable connection, recognisable by the RJ-45 connector. Compared with Wi-Fi it is steadier and has lower latency; gamers and people on video calls will notice.

F

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Firewall

Protection in the router and in the operating system that watches traffic between the home network and the internet and discards connections that are not permitted.

Frequency band

The range of frequencies a link transmits on. The free bands (2.4 and 5 GHz) are used by everybody and tend to be congested; licensed bands are reserved for the provider alone.

FTTH and FTTB

Fibre brought all the way into the flat (FTTH) or into the building (FTTB), from where the last stretch runs over copper. The difference shows in the speed you can reach.

FUP

Fair use policy, under which the provider reduces the speed once a set volume of data is exceeded, so that one customer does not swamp the line for the others.

G

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Gigabit

A thousand megabits per second, that is 1000 Mb/s, which in an ordinary household is enough for several 4K streams at once.

GPON

A fibre network technology in which a single strand from the exchange is split between several dozen households, which is why fibre has aggregation too.

H

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HD, Full HD and 4K

Picture resolution. A Full HD stream needs roughly 5 Mb/s, for 4K you should count on 25 Mb/s, and that is for each television running at the same time.

Hotspot

A place with public Wi-Fi. One can also be made out of a phone, which then shares its mobile data with other devices.

HTTPS

An encrypted connection to a website, recognisable in the browser by the padlock next to the address. Nobody along the way can read what you send, such as a password or a card number.

CH

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Smart home

Devices controlled over the network: lights, thermostats, sockets, cameras. Most of them hang off the Wi-Fi. The more of them there are at home, the more important signal coverage across the flat becomes.

I

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IP address

The numerical address of a device on the network. Your household has one address facing outwards and the router hides all the devices in the flat behind it.

IPTV

Television carried over the internet instead of an aerial or a satellite. It offers catch-up, recording and watching on a phone (see our television offer).

IPv4 and IPv6

Two versions of addressing. The older IPv4 addresses are in short supply, which is why IPv6, with a far larger supply, is gradually being rolled out. An ordinary user will not notice the difference.

ISP

The internet service provider, in our case PražskýNET.

J

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Jitter

Variation in latency. When the ping swings from 20 to 200 ms and back, a video call stutters even though the line speed is high.

To a

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Coaxial cable

A round cable with a conductor in the middle and shielding around it, carrying the television signal and, on cable networks, the internet as well.

Codec

A way of compressing picture and sound. A newer codec (H.265 against H.264) carries the same picture with markedly less data.

RJ-45 connector

The eight-pin end of a network cable. It clicks into the socket in a router, a computer or a television.

Twisted pair

An ordinary network cable, marked UTP or STP and by categories Cat 5e, Cat 6 and above. A higher category handles a higher speed over a longer distance.

L

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LAN

The local network, that is everything connected at your home behind the router. Devices on it talk to each other directly and the data does not go anywhere outside.

Latency

The response time of the network, measured in milliseconds. It decides how quickly a server answers, and for games and video calls it matters more than line speed.

LoRa

A radio network for small volumes of data over long distances. It is used by sensors and meters; the Helium project is built on this technology too, see Free internet.

LTE

The technical name for fourth-generation mobile networks, commonly called 4G.

M

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MAC address

The fixed identifier of a network card, written as six pairs of characters, by which a device on the network can be recognised or given a permanent IP address.

Mb/s

Megabit per second, the unit of connection speed. Not to be confused with MB/s (megabyte), which is eight times more.

Mesh

Several Wi-Fi units forming a single network under the same name. When you move between rooms the device switches over by itself and nobody switches anything by hand.

Microwave link

A wireless link between two antennas with a clear line of sight. This is how, with a connection over the air, the signal reaches the building without digging or drilling.

Modem

A device that converts the provider's signal into network traffic. There are several kinds depending on the technology: a DSL modem for the telephone line, an optical one for fibre, an LTE modem with a SIM card. It is often combined in one box with the router.

N

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NAT

Address translation in the router, thanks to which a whole household gets by with a single public address.

No data cap

A plan with no data cap and no slowdown once a volume is used up. With mobile plans it is worth checking whether it also applies to sharing data with a laptop.

O

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ONT

The terminal unit of a fibre connection, where the fibre ends and from where an ordinary network cable runs on to the router.

Optical fibre

A glass strand along which data travels as light. It has no trouble with interference or distance and handles speeds in the order of gigabits.

P

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Packet loss

Packet loss. Some of the data disappears on the way and has to be sent again, which shows up as a call or a stream breaking up. Even a few per cent is noticeable.

Ping

A latency test. The device sends a packet and measures how long it takes to come back. The result in milliseconds is the quickest way to tell whether the line is alive.

PoE

Power over the network cable. An outdoor antenna or camera then needs no socket of its own; power and data go down one cable.

Port

A number that distinguishes individual services within one IP address. The web runs on port 443, e-mail on another. Port forwarding is set up when a device on the home network is to be reachable from outside.

PPPoE

Logging on to the provider's network with a username and password entered into the router. You will come across it with DSL connections.

Proxy

An intermediary that internet traffic passes through. Companies use it to filter and to cache frequently visited pages.

Connection point

The physical end of the network at the customer's: a socket, an optical unit or an antenna on the roof. Beyond it, the home network begins.

R

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Roaming

Using a mobile plan on a foreign network. In EU countries the same prices apply as at home. Outside it the rates differ by operator.

Router

The box that distributes the connection around the household and usually broadcasts the Wi-Fi as well. Where it stands matters more than people expect: it does not belong in a cupboard or behind the television.

Connection speed

It is given as two numbers, for example 50/5 Mb/s: the first is the download speed, the second the upload speed. It is the speed measured at the connection point. Inside the flat the Wi-Fi affects it further.

S

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Server

A computer that runs somewhere without interruption and answers other people's requests, whether for pages, e-mails or streams.

Set-top box

A receiver that turns the television service into a picture for the TV set. With IPTV it connects by cable or Wi-Fi and is controlled with its own remote.

SIM card

A card holding subscriber details by which the mobile network recognises you. It also fits modems for connecting a household over 4G and 5G.

SSID

The name of a Wi-Fi network that you see in the list when connecting. It can be changed and even hidden, but that adds nothing to security.

Streaming

Playing video or music continuously from the internet without downloading the whole file, the way Netflix, YouTube and internet television do.

Switch

A splitter for network cables. It adds more sockets when the ports on the router are not enough; on its own it does not distribute the internet.

Symmetrical connection

A line with the same download and upload speed, for example 100/100 Mb/s. It is appreciated by anyone who sends large files, backs up to the cloud or streams.

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Encryption

Encoding transmitted data so that nobody reads it on the way. It applies to Wi-Fi (WPA2, WPA3) as well as to connections to websites (HTTPS).

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Plan

A particular service offer: speed, price, any commitment and what is included. You will find an overview in the internet offer.

TCP/IP

The set of rules by which devices on the internet communicate. IP takes care of addressing, TCP of making sure the data arrives complete and in the right order.

U

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Upload

Uploading data outwards from you: sending photos, a backup to the cloud, the picture from your camera on a video call. The second number in the fraction of a plan.

URL

The full address of a page including the protocol, for example https://prazskynet.cz/en/glossary.

V

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VDSL

The faster successor to ADSL over the telephone line, where the speed you can reach falls with distance from the exchange.

Public IP address

An address reachable from the internet. Without it you cannot connect home from outside, whether to a home server or to storage.

Video library

An archive of films and series that can be played at any time, independently of the broadcast schedule; it is usually part of the television packages.

VoIP

Making calls over the internet instead of over a traditional line. Call quality is decided by latency and packet loss; a fast line on its own is not enough.

VPN

An encrypted tunnel between your device and a remote network, used for working from home or for connecting safely over somebody else's Wi-Fi.

W

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WAN

The side of the router facing the provider. The cable from the modem or from the connection point goes into the WAN socket; the devices in the flat plug into the rest.

Wi-Fi

The wireless connection of devices to the router. It has nothing to do with the speed of the connection itself. Slow Wi-Fi can spoil even a gigabit line when the signal does not reach across the whole flat.

Wi-Fi 6 and 6E

Newer generations of Wi-Fi. They pay off where many devices are connected at once; 6E also broadcasts in the 6 GHz band, where there is no congestion yet.

WPA2 and WPA3

Ways of securing Wi-Fi with a password. WPA3 is newer and more resistant to password guessing. The older WEP should no longer be used today.

X

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xDSL

The collective name for connections over the telephone line: ADSL, VDSL and other variants.

Z

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Commitment

The period during which a contract cannot be terminated without a penalty. Our plans have no commitment.

Catch-up

Playing a programme that has already been broadcast, with our television packages up to seven days back.