Infrastructure Framework  «Prev  Next»
Lesson 4 Backbones and Network Access Points
Objective Describe the purpose of backbones and Network Access Points and how they relate to each other.

Backbones and Network Access Points

The internet backbone, a vital part of global communications, consists of numerous high-capacity data routes that interconnect different networks around the world. Two critical components of this structure are backbones and network access points (NAPs), each playing a distinct role in ensuring efficient and reliable internet connectivity.


  1. High-Capacity Transmission: Backbones are comprised of high-speed lines or fiber-optic cables, which serve as the primary pathways for data transfer across the internet. They are designed to handle large volumes of traffic, ensuring rapid data transmission between distant points.
  2. Interconnection of Networks: These backbones connect various smaller networks, such as local area networks (LANs) and regional networks, to the wider internet. This interconnection is crucial for facilitating global communication.
  3. Redundancy and Reliability: The backbone network is typically designed with redundancy, meaning there are multiple pathways for data to travel. This redundancy ensures that if one path fails or becomes congested, data can be rerouted, thereby maintaining network reliability and uptime.
  4. Scalability: Backbone networks are scalable, allowing for expansion to accommodate increasing internet usage and new technologies without significantly altering the existing infrastructure.

Network Access Points (NAPs):

  1. Inter-network Exchange: NAPs are key junction points where different internet service providers (ISPs) connect their networks. These points allow for the exchange of internet traffic between ISPs, which is essential for accessing resources hosted on different networks.
  2. Traffic Routing and Management: At NAPs, traffic is analyzed, and routing decisions are made based on network policies, traffic load, and the destination of data. This routing is crucial for optimizing the flow of internet traffic and maintaining efficient network operation.
  3. Reduction of Bottlenecks: By efficiently managing traffic at these points, NAPs help reduce potential bottlenecks that can occur when large volumes of data converge from multiple sources.
  4. Support for Diverse Technologies: NAPs are equipped to handle various types of communication protocols and data formats, making them versatile points for interconnecting diverse networks.

In summary, backbones and network access points are foundational elements of the internet backbone, working in tandem to facilitate high-capacity data transmission, ensure network reliability and scalability, enable inter-network communication, and manage internet traffic efficiently. Their roles are pivotal in maintaining the global internet infrastructure's functionality and performance.

What exactly is a backbone?

If you request a Web page, that information often has to cross several networks before it gets to you. Those networks that it crosses are called backbones. Without backbones it would be nearly impossible for you to receive the information you asked for. The Internet backbone comprises very high-bandwidth lines interconnected with fast, high-capacity routers. In brief, backbones are high-speed networks that carry Internet traffic. Commercial backbone providers include PSINet, UUNET, ANS/AOL, Sprint, AT&T, GTE, IBM, and MCI.

What is a backbone ISP?

In the image below you will notice that major ISPs and smaller networks are connected directly to a backbone ISP. The backbone ISPs are unique in that they carry high-speed connections between them and are ultimately responsible for transporting information over the network. National long-distance carriers or the government generally install backbone lines.
A backbone ISP, also known as a Tier 1 provider, is the **internet's equivalent of a highway system**. Just like highways connect cities and towns, backbone ISPs connect major networks and data centers around the world, forming the core infrastructure that carries the massive amount of data traffic we generate every day. Imagine the internet as a massive web, with individual users and smaller ISPs being the local roads and smaller towns. Tier 1 ISPs are the high-speed highways that connect these smaller networks, allowing data to flow smoothly and efficiently across vast distances. Here are some key characteristics of backbone ISPs:
  • Global reach: They have extensive networks spanning multiple continents, with connections to major internet exchange points (IXPs) around the world.
  • High bandwidth: They can handle enormous amounts of data traffic, often exceeding 100 Gbps or even 1 Tbps.
  • Redundancy: They have multiple backup paths for data to travel in case of outages or congestion, ensuring high availability and reliability.
  • Peering agreements: They exchange traffic with other Tier 1 providers through peering agreements, which allows for efficient data exchange without incurring charges.
  • Limited customer base: Unlike your local ISP, Tier 1 providers typically don't directly serve individual users. They primarily sell their services to other ISPs, content providers, and large enterprises.

Here's an image to help visualize the role of backbone ISPs in the internet ecosystem:
ISP BackBone
ISP BackBone

As you can see, Tier 1 ISPs sit at the top of the hierarchy, forming the backbone of the internet. Tier 2 ISPs connect to Tier 1s and then provide services to smaller regional ISPs (Tier 3) who, in turn, serve individual users and businesses. Backbone ISPs play a critical role in ensuring the smooth functioning of the internet. They are responsible for carrying the vast majority of the world's internet traffic, and their performance and reliability directly impact our online experience.

The Internet backbone
The Internet consisting of Backbone ISP and Server's Regional ISPs

What exactly are NAPs?

Backbones join at network access points (NAPs). As the name implies, network access points are the entryways to the Internet. For example, think of all the people from around the world who come to San Francisco to cross the Golden Gate Bridge. They all meet up at the toll plaza before crossing. The toll plaza is equivalent to the network access point. It's a universal gateway. Network access points tie various ISPs and the national telecommunications companies. NAP examples include Sprint and Worldcom. They provide routing flexibility, bandwidth savings, and permit reduction of network lengths. Here are examples of both public and private NAPs.

Ad IP Subnetting
Public NAPS (Networks Access Points)
Public NAPS with Networks Access Points

Private NAPS (Networks Access Points)
Private NAPS (Networks Access Points)
In the next lesson, the specific hardware and software network connection devices will be discussed.
SEMrush Software