The Internet, as the name suggests, is a complex ‘network of networks’. And sending an email or opening a web page requires data to transmit multiple networks, owned and operated by different Internet service providers (ISPs). Policymakers working to improve the availability and affordability of high-speed internet services, or broadband, need to understand how data moves across the millions of miles of pipes, cables, wires and other equipment owned by different ISPs between users across the country and beyond. the world.
Three main components of broadband networks are interconnected to route data from point to point on the Internet:
- The spine consists of large fiber optic conduits, often buried deep underground, that are the main data routes on the Internet and the primary path for Internet traffic between countries.
- The middle mile is the part of a network that connects the backbone to the last mile and is also known as ‘backhaul’. They are usually fiber optic lines, but can be wireless and in some cases can deliver the internet directly to large customers such as schools or health centers.
- The last mile is the segment that connects a local ISP to a customer, for example via a cable line to the home. The type of technology used to deliver last-mile service is the primary determinant of the speed and quality of service available to consumers.
ISPs, which can be municipal utilities, electric and telephone cooperatives, or private companies such as cable or telephone companies, fall into three tiers based on how they transport and exchange data between networks. These ratings are determined by the carrier’s geographic reach and whether they pay for “transit” on other carriers’ networks.
- Tier 1: Major providers that own, operate, and maintain infrastructure, including the Internet backbone. These ISPs, including AT&T, Deutsche Telekom, Lumen (CenturyLink), Verizon and Zayo, have global reach. Because they all carry roughly the same amount of data on their networks, the costs they each incur — and the fees they can charge each other — for exchanging data across networks is essentially the same. As a result, they exchange free traffic based on mutually beneficial arrangements.
- Level 2: Providers, typically major cable providers and multi-state telecommunications companies such as Comcast, Cox, Frontier, and TDS, who exchange data for free with other providers in some parts of their network, but purchase transit services that allow them to move user data through another’s network provider, to reach other parts of the Internet.
- Tier 3: Usually last-mile service providers or providers that only provide direct connections to customers who need to purchase access to the wider internet, either through direct contracts with Tier 1 providers or by purchasing services from a Tier 2 provider that provides connections with Tier 1 include networks.
Contracts, also known as interconnection or peering agreements, regulate the exchange of data between the networks of different ISPs, allowing data to travel freely around the world. The exchanges take place at Internet Exchange Points (IXPs), usually large buildings where multiple providers house equipment to link their networks and transfer data. Network switches within IXPs work just like railroad switches, sending data from one ISP to another to ensure it travels along the most direct route and to the right destination.
That online content that we access on our computers and phones is largely generated by ‘edge providers’, usually large companies in retail, social media, technology or video streaming, but sometimes individuals who provide content such as websites, web applications or web hosting services .
The transfer of this data is powered by Content Delivery Networks (CDNs), systems of servers around the world, typically owned by major technology companies such as Amazon CloudFront and Akamai, which improve the efficiency of data transmission over the Internet. Acting as data warehouses, CDNs store copies of web content in various locations to reduce the time between clicking a link and loading a web page. CDNs connect to the ISP-managed networks and speed up the transfer of data by “sending” content from a nearby facility — rather than having to travel from the edge provider’s headquarters — to the end user.
The internet speeds customers experience are determined by the slowest link in this system — usually the last mile — and depend on two related network metrics:
- Bandwidth is the volume of data a network can transmit, expressed in megabits per second (Mbps). More bandwidth means a faster connection.
- Throughput is the amount of data that can pass through a communication system.
The relationship between them is akin to a road. Bandwidth is the number of lanes and throughput is the amount of traffic. The wider the road, the more traffic it can carry at full speed before it clogs and slows down. The backbone is most like a highway and offers high bandwidth, while the middle mile could be a major urban thoroughfare and the last mile more like a residential street.
However, congestion can occur on any part of the network. For example, a last mile provider may have enough bandwidth to serve its local customer base, but traffic may be slowed down by congestion at the point of connection to the middle mile portion of the network.