The Internet as a Network: Understanding ISP, LAN, POP, NAP & more

  • Tom Goldsworthy
  • 06-Mar-2017 10:25:00
  • Telecoms

Best VoIP Phone Sysetm Provider Internet PoP Infrastructure.jpgIn our second blog in our series explaining how the Internet works, we look at the Internet as a network—the different components that make up that network, and how they speak to each other. After all, every computer that is connected to the Internet is part of a network. Click on each bolded term to learn what it means.

A Hierarchy of Networks

You may have set up a Local Area Network (LAN) at home if you have more than one computer, and you will certainly have a LAN at work that allows the office computers and printers to communicate with each other directly, but you will still connect to the Internet using an ISP that your company has contracted with. When you connect to your ISP (BT, Virgin, TalkTalk, VTSL), you become part of their network. The ISP may then connect to a larger network and become part of their network. The Internet is simply a network of networks.

Most large communications companies have their own dedicated backbones connecting various regions. In each region, the company has a Point of Presence (POP). The POP is a place for local users to access the company's network, often through a dedicated line. The amazing thing is that there is no overall controlling network. Instead, there are several high-level networks connecting to each other through Network Access Points or NAPs.


Imagine that Company A is a large ISP. In each major city in the UK, Company A has a POP. Company A leases fiber optic lines from a leased line telecoms provider (Openreach)  to connect the POPs together.

Imagine that Company B is a corporate ISP. Company B builds large buildings in major cities across the UK and corporations locate their Internet server machines in these buildings. Company B is such a large company that it runs its own fiber optic lines between its buildings so that they are all interconnected.

In this arrangement, all of Company A's customers can talk to each other, and all of Company B's customers can talk to each other, but there is no way for Company A's customers and Company B's customers to intercommunicate. Therefore, Company A and Company B both agree to connect to NAPs in various cities, and traffic between the two companies flows between the networks at the NAPs.

In the real Internet, dozens of large Internet providers interconnect at NAPs in various cities, and trillions of bytes of data flow between the individual networks at these points. The Internet is a collection of huge corporate networks that agree to all intercommunicate with each other at the NAPs. In this way, every computer on the Internet connects to every other.

Talking to Each Other

All of these networks rely on NAPs, backbones and routers to talk to each other. What is incredible about this process is that a message can leave one computer and travel halfway across the world through several different networks and arrive at another computer in a fraction of a second.

The routers determine where to send information from one computer to another. Routers are specialised computers that send your messages and those of every other Internet user speeding to their destinations along thousands of pathways. A router has two separate, but related, jobs:

  • It ensures that information doesn't go where it's not needed. This is crucial for keeping large volumes of data from clogging up connections.
  • It makes sure that information does make it to the intended destination.

In performing these two jobs, a router is extremely useful in dealing with two separate computer networks. It joins the two networks, passing information from one to the other. It also protects the networks from one another, preventing the traffic on one from unnecessarily spilling over to the other.


We mentioned backbones earlier.  Backbones are fiber optic trunk lines with multiple fiber optic cables combined together to increase the capacity, that connect larger networks.

Today there are many companies that operate their own high-capacity backbones, and all of them interconnect at various NAPs around the world. In this way, everyone on the Internet, no matter where they are and what company they use, is able to talk to everyone else on the planet.

And with that you now have the basics of the network infrastructure that makes the internet work.  Our next blog will look at IP addresses, domains, clients and servers, and ports.


About VTSL

VTSL is a leading hosted communications specialist, ISP and VoIP business phone system provider.  Founded by Robert and David Walton over 10 years ago, VTSL take pride in developing relationships and partnerships with their clients over the long term. Whether a big business, or small start up, VTSL’s VoIP business phone system offers a professional and cost effective telephony system for organisations who want to get ahead. Learn more about what VTSL can do for your business by clicking here: BEST VOIP PHONE SYSTEM PROVIDER or calling 0207 078 3200.


Topics: Telecoms