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  • Glossary
  • What is the internet backbone? | ExpressVPN Glossary

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Internet backbone

Internet backbone

What is the internet backbone?

The internet backbone is the core infrastructure of the global internet. It carries large volumes of internet traffic and forms the central pathways that allow networks around the world to communicate.

Internet backbone infrastructure

The internet backbone relies on several key infrastructure components that enable global data transport:

  • Fiber-optic cables: Long-distance terrestrial and submarine fiber links carry internet traffic between regions and continents.
  • Backbone routers: High-capacity routers forward data between networks and maintain large routing tables.
  • Points of presence (PoPs): Facilities in major cities where backbone providers house networking equipment and connect their infrastructure to local networks.
  • Internet exchange points (IXPs): Neutral locations where different networks interconnect and exchange traffic directly.

How does the internet backbone work?

Once traffic reaches the backbone, backbone routers determine the best available path to its destination. These routers communicate using Border Gateway Protocol (BGP), which maintains a continuously updated map of reachable networks and the routes used to reach them.

Based on this information, each router forwards the data packet to the next network along the selected path. Networks typically interconnect at PoPs or IXPs, where providers exchange traffic.

If a route becomes unavailable or congested, routers can select alternative paths, allowing traffic to continue moving across the backbone.Simple diagram showing a device sending traffic to a local ISP, the internet backbone carrying it across long-distance networks to a server, and a backup path rerouting traffic if the main route fails.

Who owns the internet backbone?

No single entity owns the internet backbone. It is operated collectively by a small number of large carriers, known as Tier 1 providers, which maintain peering agreements that allow them to exchange traffic with one another. Smaller regional and local providers pay Tier 1 carriers for access to this broader network, a cost that is eventually passed down to end users.

Architecture and constraints

The internet backbone is designed to carry large volumes of traffic across interconnected global networks. Its architecture introduces certain constraints that shape how traffic is routed and how disruptions are handled:

  • Physical disruptions: Submarine and terrestrial fiber cables can be damaged by natural events or human activity, which may interrupt connectivity until traffic is rerouted.
  • Routing trust model: BGP relies on trust between networks when exchanging routing information. In some cases, incorrect or unauthorized route announcements can affect how traffic is directed, though such issues are typically limited in scope and resolved by network operators.
  • Network concentration: A relatively small number of major carriers and interconnection points handle significant global traffic, which can increase the impact of outages or disruptions in key areas.

Further reading

FAQ

What is the difference between the internet backbone and an ISP?

The backbone is the high-capacity infrastructure that carries traffic across long distances, while internet service providers (ISPs) are the companies that connect end users to that infrastructure.

Can the internet backbone be disrupted?

Threats that can affect the backbone include Border Gateway Protocol (BGP) hijacking, traffic interception, and distributed denial-of-service (DDoS) attacks. That said, large-scale disruption is rare due to the network's distributed architecture.

How do submarine cables support the backbone?

Submarine cables are the physical extension of the backbone across oceans, carrying the vast majority of international internet traffic between continents.

Does VPN traffic travel through the internet backbone?

Yes. Virtual private network (VPN) traffic is encrypted before it enters the network, but still travels through the same backbone infrastructure as any other internet traffic.
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