What is an ISP

Thomas Gilham
We tend to think of the internet as a “place” that’s “out there” somewhere and that an Internet Service Provider (ISP) is the gateway or “on ramp” to gives us access to that place. While a useful metaphor, it’s not quite accurate.

In reality, there is no “place” call the internet, just a vast number of computers and other online resources that each have a public address (called a URL). Certain record-keepers such as domain name servers (which track and assign URLs) are collectively known as the “backbone” of the internet, but the internet itself is simply the interaction between all of the computers.

In the earliest days of online networks, there were no URLs or IP addresses or a “true” internet. Instead, a smaller number of computers (or online resources) were kept inside a gated community. CompuServe and American Online (AOL) in their original form were such a network. They did offer their customers the ability to exchange information with one another (via chat rooms, websites, and email), but not with non-customers.

The first true ISPs emerged in 1989 in the United States and Australia and today, every country on the planet has ISPs. Originally, customers would use a dial-up modem to connect to the ISP’s computers which were then connected to the internet at large. Today, most ISPs are accessed either wirelessly (primarily via Wi-Fi) or by cable. Since internet via cable is much faster than the earlier closed, dial-up networks, it is often identified as being “broadband” or able to transmit more information more rapidly. Nearly all ISPs today offer broadband level internet access.

You can also now connect to an ISP via fiber-optic cable (sometimes called FiOS) that allows even faster data transfers than via cable. Other options for connecting to the internet (at “broadband” speeds) include DSL (digital subscriber line), ADSL (asymmetric digital subscriber line), Ethernet, Frame Relay, ISDN (Integrated Services Digital Network), ATM (Asynchronous Transfer Mode), and SONET (Synchronous Optical Network). Wireless access (which may or may not be “broadband” quality) include via mobile/cellular phone companies (2G, 3G, 4G, 5G, LTE, etc), via satellite, and via Wi-Fi (IEEE 802.11).

If you’re accessing the internet from home, you’re most likely getting your internet from an ISP that also offers other services such as cable television, and a landline phone. Other ISPs, however, exclusively provide access to the internet. Most ISPs also offer additional internet services such as an email address (which connects to an email server that they manage).

You can also access the internet from a school network or an office network. In this case, the network is also connected to an internet service provider. But unlike an internet connection from home, the ISP’s customer is the school or the office. This is an important distinction when it comes to IP addresses, which are assigned by the ISP.

When you want to connect to the internet, your computer uses a network interface controller (NIC) to search for an available network. Assuming you’re at home and have a router provided by your ISP, the available network information will be provided by that router. The router will then contact your ISP and request access to the internet. The ISP will verify that you have an account with them in good standing and then tell the router to assign you an IP address and grant you access to the internet. Your IP address will then serve as a unique identifier for your device (computer, smartphone, etc.) as you interact with the internet.

The IP address that your router assigns you is a collection of two-digit hexadecimal numbers that contains information about the ISP. The IP address will usually contain information such as the name of the ISP, the country that you’re in, the city that you’re in, and even sometimes the street or neighborhood where you are located. This is useful when performing actions that use your location such as finding nearby restaurants, but you may not always want every website to know exactly where you are located.

And while we are most familiar with commercial ISPs that charge a fee for internet access and other services (like email), some ISPs are non-profit in nature and provided by organizations like universities, schools, religious groups, government agencies, and co-ops.

ISPs are ranked in something called tiers, where lower numbers mean higher-level access. When you log into an ISP to connect to the internet, your ISP is probably connecting to other ISPs in order to receive access, and these higher tier ISPs will connect to yet more ISPs until they are given access to the internet by a Tier 1 ISP. A Tier 1 ISP is the only type of ISP that can access every resource on the internet without having to pay for or negotiate access. Tier 1 ISPs form part of the internet’s “backbone.”

Even more confusingly, your ISP itself will have multiple Points-of-Presence (PoP) or access points to the internet. For instance, your ISP may have one PoP for web traffic and a different PoP for email traffic. Servers, routers, switches, and other devices mean that some bigger ISPs can have hundreds if not thousands of PoPs. Each of these PoPs will have separate connections to more powerful ISP tiers.

The issue of Net Neutrality refers to laws and regulations which compel ISPs to provide equal access (and data transmission speeds) for all users, all data types, and all of their PoPs.

Many ISPs provide email services, but not all email service providers are ISPs. Besides just handling the data transfer needed to send and receive emails, these email service providers also host/store your email as well as generating email addresses. Other services provided by ISPs include online storage (sometimes called “the cloud”), web hosting, and both virtual and physical servers (which can perform as a web host).

There’s also such thing as a virtual ISP wherein one ISP will lease or rent internet access to companies that then function as an ISP and charge customers for internet access. In some countries, the only true ISP is a state-owned telecom company that then leases or rents internet access to third-party companies.

By law, ISPs in many countries (including the United States and Britain) are required to allow law enforcement agencies to monitor or access the data that passes through their computers. In other cases, ISPs may record and analyze their users’ internet activity and may block users from accessing certain websites or online resources. Keep in mind that even if you’re using a browser in incognito/private mode and/or using a proxy server, your ISP will always have the ability to monitor your online activity.