Modern Internet Backbone

- Overview

The Internet backbone is a high-speed network infrastructure that transmits large amounts of data over the Internet. It is a core part of the global Internet, connecting Internet Service Providers (ISPs) and other networks around the world. In other words, it's like the highway system of the Internet. This backbone provides the foundation for the Internet, allowing data to be transmitted around the world in seconds. 

The Internet backbone is a complex network of fiber optic cables, routers, switches and other network equipment that work together to transport data between different Internet service providers. It is a distributed network consisting of multiple interconnected networks located around the world. These interconnected networks are managed by various organizations that work together to maintain order and ensure fast data transfer to all parts of the world. 

The purpose of the backbone network is to provide connectivity between different networks and areas and to facilitate communication between them. It is the fastest, most reliable communications network and is critical to the functioning of the entire Internet.

- No One Owns The Internet All

The backbone network of the Internet is not owned by any single company or organization. No government can lay claim to owning the Internet, nor can any company.

Instead, it is made up of multiple large interconnected networks that work together to provide seamless connectivity around the world. Some of the most well-known Internet backbone providers include Level 3 Communications, Verizon, AT&T, and Deutsche Telekom.

The Internet is more of a concept than an actual tangible entity, and it relies on a physical infrastructure that connects networks to other networks. The Internet is like the telephone system - no one owns the whole thing. 

Today, several large corporations provide the routers and cable that make up the Internet backbone. These companies are upstream Internet Service Providers (ISPs).  There are many organizations, corporations, governments, schools, private citizens and service providers that all own pieces of the infrastructure. 

There are, however, organizations that oversee and standardize what happens on the Internet and assign IP addresses and domain names, such as National Science Foundation, the Internet Engineering Task Force, ICANN, InterNIC and the Internet Architecture Board. 

Because of the enormous overlap between long-distance telephone networks and backbone networks, the largest long-distance voice carriers such as AT&T, Verizon, Sprint, and CenturyLink also own some of the largest Internet backbone networks. These backbone providers sell their services to Internet service providers (ISPs). Each ISP has its own contingency network and is equipped with an outsourced backup. 

These networks are intertwined and crisscrossed to create a redundant network. Many companies operate their own backbones which are all interconnected at various Internet exchange points (IXPs) around the world. 

In order for data to navigate this network, there needs to be backbone routers that are powerful enough to handle the information on the Internet backbone and capable of directing the data to other routers to send it to its final destination. Without them, information would be lost.

- Tier 1 ISPs

Like any other network, the Internet consists of access links that move traffic to high-bandwidth routers that move traffic from its source over the best available path toward its destination. This core is made up of individual high-speed fiber-optic networks that peer with each other to create the internet backbone. 

The individual core networks are privately owned by Tier 1 ISPs, giant carriers whose networks are tied together. These providers include AT&T, CenturyLink, Cogent Communications, Deutsche Telekom, Global Telecom and Technology (GTT), NTT Communications, Sprint, Tata Communications, Telecom Italia Sparkle, Telia Carrier, and Verizon. 

Today, these large corporations provide the routers and cable that make up the Internet backbone. These companies are upstream ISPs. By joining these long-haul networks together, Tier 1 ISPs create a single worldwide network that gives all of them access to the entire Internet routing table so they can efficiently deliver traffic to its destination through a hierarchy of progressively more local ISPs. 

Please refer to Wikipedia: The Internet Connectivity Distribution for more details.

- Internet Exchange Points (IXPs)

Internet exchange points (IXP) tie the backbone together. Backbone (Tier 1) ISPs connect their networks at peering points, neutrally owned locations with high-speed switches and routers that move traffic among the peers. These are often owned by third parties, sometimes non-profits, that facilitate unifying the backbone. Participating Tier 1 ISPs help fund the IXPs, but don’t charge each other for transporting traffic from the other Tier 1 ISPs in a relationship known as settlement-free peering. Such agreements eliminate potential financial disputes that might have the result of slowing down Internet performance.

The Internet backbone is made up of the fastest routers, which can deliver 100 Gbps trunk speeds. These routers are made by vendors including Cisco, Extreme, Huawei, Juniper, and Nokia, and use the border gateway protocol (BGP) to route traffic among themselves.

- Tier 2 and Tier 3 ISPs

Below the Tier 1 ISPs are smaller Tier 2 and Tier 3 ISPs. Tier 3 providers provide businesses and consumers with access to the Internet. These providers have no access of their own to the Internet backbone, so on their own would not be able to connect their customers to all of the billions of Internet-attached computers. Buying access to Tier 1 providers is expensive. So often Tier 3 ISPs contract with Tier 2 (regional) ISPs that have their own networks that can deliver traffic to a limited geographic area but not to all Internet-attached devices. In order to do that, Tier 2 ISPs contract with Tier 1 ISPs for access to the global backbone, and in that way make the entire internet accesssible to their customers. 

This arrangment makes it possible for traffic from a computer on one side of the world to connect to one on the other side. That traffic goes from a source computer to a Tier 3 ISP that routes it to a Tier 2 ISP that routes it to a Tier 1 backbone provider that routes it to the appropriate Tier 2 ISP that routes it to a Tier 3 access provider that delivers it to the destination computer.

- Internet Connectivity Distribution

A Tier 1 network is an Internet Protocol (IP) network that can reach every other network on the Internet solely via settlement-free interconnection (also known as settlement-free peering). 

Tier 1 networks can exchange traffic with other Tier 1 networks without having to pay any fees for the exchange of traffic in either direction, while some Tier 2 networks and all Tier 3 networks must pay to transmit traffic on other networks.

[More to come ...]