An internet primer: connectivity

We discussed in the first article in this series how our internet service provider (ISP) connects us to the internet. Here we look at how we connect to each other and our ISP and what other technologies are at work influencing our internet connectivity and experience.

Modems and routers

A modem (modulator-demodulator) converts data from a digital format, intended for communication directly between devices, into one suitable for a transmission medium. Most commonly, modems turn computer data into a modulated electrical signal for transmission over telephone lines. Alongside this, a router allows multiple computers to share one connection.

ISPs now provide gateways which combine the modem and broadband router into a single package that provides also network address translation (NAT), security features and WiFi access. Consequently the terms “modem”, “router” and “gateway” are now used interchangeably in everyday speech.

Private networks

Whether from home or work, we are almost all now connected to a local area network (LAN), which is simply a network that connects computers and devices in a limited geographical area. It may be wired or wireless. Wired LANs mostly use Ethernet technology (an IEEE standard). A LAN which connects digital devices in the home is known as a home area network (HAN).

Commonly an intranet is used as the internal LAN of an organisation. An intranet uses the IP protocol and IP-based tools such as web browsers and file transfer applications. An extranet supports a limited connection to a specific external network, for example, a business partner’s.

A virtual private network (VPN) encrypts your internet traffic and disguises your online identity, making it more difficult for others to track your activities online and access your data. A VPN hides your IP address by letting the network redirect it through a specially configured remote server run by a VPN host which becomes the source of your data. Your ISP and others cannot see which websites you visit or what data you send and receive online. Even if someone were to get their hands on your data, it would be useless as it is encrypted.

A darknet is accessible through specialised technology, such as Tor, I2P and Freenet, which make connections only between trusted peers, using non-standard protocols and ports. Darknets are used for legitimate purposes, such as anonymous communication between whistle-blowers, activists, journalists and news organisations, and for illegal reasons such as drug trafficking.

Cellular networks and smartphones

A cellular (or mobile) network is so called as it connects areas called cells, each of which is served by, usually, three base transceiver stations. These stations provide the network coverage which can be used for transmission of all types of digital content. To avoid interference and provide guaranteed service quality, each cell uses a different set of frequencies from neighbouring cells.

Portable transceivers can communicate with each other and with fixed devices anywhere in the network, via base stations, even when moving through more than one cell during transmission.

The US Bell System had developed cellular technology as long ago as 1947, but the first generation commercial cellular network (now referred to as 1G), was launched by Japan’s Nippon Telegraph and Telephone (NTT) in 1979.

The advent of smartphones, with the release of Apple’s iPhone in 2007, facilitated internet access and web browsing as well as multimedia functionality, alongside the core phone functions of voice calls and text messaging. Smartphones are essentially very small, high-powered, portable computers, supporting wireless communications protocols such as WiFi, Bluetooth and satellite navigation.

The smartphone gave rise to small applications specifically designed for mobile devices, commonly called “apps”. Native mobile apps are built for a specific platform, such as Apple iOS or Android. They are downloaded and installed via an app store and, crucially for present purposes, have access to system resources such as WiFi, Bluetooth, and satellite navigation.


Wi-Fi (or WiFi) is a technology for wireless local area networking developed and trademarked by the Wi-Fi Alliance. The Alliance restricts the use of the term “Wi-Fi Certified” to products that successfully complete interoperability certification testing.

A WiFi access point or “hotspot” has a range of about 20 meters indoors, more outdoors. Indoors, walls will diminish or block the radio waves and other devices may interfere with them. Outdoors, hotspots as large as many square kilometres can be achieved using multiple overlapping access points. For example, public outdoor WiFi technology has been used successfully in wireless mesh networks in London. Internationally, Fon Wireless is the leading global WiFi network, having built a WiFi community of over 21 million hotspots through partnerships with telcos.

As anyone within range can attempt access, WiFi networks are more vulnerable to attack or “eavesdropping” than wired networks. A family of technologies called WiFi Protected Access protect information moving across both personal and enterprise networks networks. Features constantly evolve as the security landscape changes.


Bluetooth is a wireless technology standard for exchanging data over short distances using short-wavelength UHF radio waves from fixed and mobile devices. The standard is managed by the Bluetooth Special Interest Group (SIG) with member companies in telecommunications, computing, networking and consumer electronics. A manufacturer must meet Bluetooth SIG standards to market Bluetooth devices.

A master Bluetooth device can communicate with a maximum of seven devices in an ad-hoc “piconet”. The devices can switch roles, and the slave can become the master (for example, a headset initiating a connection to a phone necessarily begins as master but may subsequently operate as the slave).

Satellite navigation

A satellite navigation system uses satellites to provide geo-spatial positioning, allowing electronic receivers to determine their location (longitude, latitude, and altitude/elevation) to within a few metres, using time signals transmitted along a line of sight by radio from satellites. It can be used for providing position, for navigation or for tracking the position of anything fitted with a receiver. Receivers can also calculate current local time to a high degree of accuracy.

A satellite navigation system with global coverage is called a global navigation satellite system (GNSS). The best known is the US Global Positioning System (GPS). Russia’s GLONASS, China’s BeiDou (BDS) and the EU’s Galileo from the Global Navigation Satellite Systems Agency (GSA) are the other global operational GNSSs. India, France and Japan are in the process of developing regional navigation and augmentation systems as well.

Satellite navigation systems operate independently of telephone or internet reception, though these technologies are used to enhance the usefulness of the positioning information.

Image: Public Domain from Piqsels.

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