Who Provides Internet Service to Your ISP?
The Infrastructure Behind Your Internet Connection
You remit payment to your Internet Service Provider (ISP) to secure internet access, and they subsequently enable data transmission. However, the question arises: where does your ISP obtain this data flow?
This exploration delves into the complexities of global data delivery, revealing the network that supports your online experience.
Understanding the Data Supply Chain
The internet isn't a single entity, but rather a vast network of interconnected networks. Your ISP is just one piece of this puzzle.
They, in turn, rely on larger networks – often called Tier 1 networks – to provide the bulk of the internet traffic.
What are Tier 1 Networks?
Tier 1 networks are massive, globally spanning networks that can reach every other network on the internet without purchasing transit from anyone else.
These networks own and operate extensive fiber optic cables, data centers, and internet exchange points (IXPs).
Key Players in Global Data Delivery
Several companies operate as Tier 1 networks, including:
- Level 3 Communications (now Lumen Technologies)
- Verizon
- AT&T
- NTT Communications
- Tata Communications
These providers have established peering agreements with numerous other networks, allowing for the direct exchange of traffic.
How Data Travels
When you request a webpage, your request travels from your computer to your ISP.
If the content is hosted on a network that your ISP has a direct connection with, the data travels directly. Otherwise, it's routed through one or more Tier 1 networks.
This complex routing process happens in milliseconds, enabling seamless internet access.
The Role of Internet Exchange Points
Internet Exchange Points (IXPs) are physical locations where different networks connect and exchange traffic.
IXPs reduce latency and improve network efficiency by allowing networks to directly peer with each other, rather than routing traffic through distant Tier 1 networks.
This information originates from a Question & Answer session hosted by SuperUser, a community-driven segment of Stack Exchange.
Understanding Internet Infrastructure
A SuperUser user named KronoS recently inquired about a fundamental aspect of the internet: how its underlying infrastructure functions.
The user expressed curiosity regarding the source of internet connectivity for Internet Service Providers (ISPs). Specifically, they asked: Who provides the Internet to the ISP? And tracing further upstream, who supplies connectivity to those providers? Is there a continuous, interconnected network that ultimately links all users?
This is a pertinent question. The internet's structure is built upon layers of interconnected networks, though these layers aren't always apparent to the average user.
The Tiered Network System
The internet doesn't originate from a single source. Instead, it operates on a tiered system of networks.
- Tier 1 Networks: These are the largest networks, possessing global reach and extensive infrastructure.
- Tier 2 Networks: These networks have significant regional or national presence.
- Tier 3 Networks: Typically, these are smaller regional or local networks.
ISPs generally fall into the Tier 2 or Tier 3 categories. They obtain internet access from higher-tier networks.
How ISPs Get Their Connectivity
Your ISP doesn't create the internet; it accesses it. They purchase transit – essentially, access to the broader internet – from Tier 1 or Tier 2 networks.
These higher-tier networks have direct connections to other major networks globally. This allows data to travel across continents and oceans.
The Interconnection of Networks
The question about a "never-ending loop" is insightful. While not a loop in the traditional sense, the internet is a highly interconnected web.
Tier 1 networks interconnect with each other through peering agreements. These agreements allow for the direct exchange of traffic between networks without charging each other transit fees.
This complex interplay of transit and peering creates a resilient and globally accessible network. It ensures that data can find its way from your computer to servers around the world.
A Continuously Expanding System
The internet’s infrastructure is constantly evolving and expanding. New networks are continually being added, and existing networks are upgrading their capacity.
This dynamic nature is what allows the internet to support the ever-increasing demands of users and applications worldwide. The system is not static, but rather a continuously developing ecosystem of interconnected networks.
Understanding Internet Infrastructure
As highlighted by SuperUser contributor Tom Wijsman, it’s possible to gain insight into the network structure supporting our internet service providers (ISPs) and the broader provider-to-provider network.
Investigating the Internet’s Foundation
Imagine lacking prior knowledge of the Internet’s history and having no access to explanatory online resources. In such a scenario, the only path to understanding the Internet’s infrastructure would be to examine its fundamental protocols. The Internet Control Message Protocol (ICMP), specifically its Echo request and Echo reply functions, provides a means to uncover the architecture of our Internet connection.
By incrementally increasing the Time To Live (TTL) value of IP packets with each iteration, you can identify each successive hop along the route to a specified destination. This process, known as traceroute, reveals a list of hops between your location and the target server. On Windows systems, the command
tracertis used, while Linux and Mac OS X utilize
traceroute.
Let’s perform a traceroute from Belgium to the United States, using Stack Exchange as our target.
Tracing route to stackexchange.com [64.34.119.12] over a maximum of 30 hops:... redacted ...5 10 ms 12 ms 12 ms te-3-3.car2.Brussels1.Level3.net [212.3.237.53]6 11 ms 11 ms 15 ms ae-0-11.bar2.Brussels1.Level3.net [4.69.148.178]7 20 ms 13 ms 15 ms ae-7-7.ebr1.London1.Level3.net [4.69.148.182]8 16 ms 16 ms 18 ms vlan101.ebr2.London1.Level3.net [4.69.143.86]9 83 ms 84 ms 87 ms ae-44-44.ebr1.NewYork1.Level3.net [4.69.137.78]10 84 ms 93 ms 97 ms ae-71-71.csw2.NewYork1.Level3.net [4.69.134.70]11 87 ms 96 ms 83 ms ae-2-70.edge1.NewYork1.Level3.net [4.69.155.78]12 84 ms 93 ms 84 ms gig2-0.nyc-gsr-b.peer1.net [216.187.123.5]13 87 ms 84 ms 85 ms gwny01.stackoverflow.com [64.34.41.58]14 87 ms 82 ms 87 ms stackoverflow.com [64.34.119.12]This reveals that Belgium, London, and New York are all interconnected via Level3. Level3 functions as an ISP for other ISPs, providing interconnection services. The following diagram illustrates this connectivity:
Now, let’s trace a route to China, targeting the Baidu search engine.
Tracing route to baidu.com [123.125.114.144] over a maximum of 30 hops:... redacted ...5 12 ms 10 ms 12 ms ae0.anr11.ip4.tinet.net [77.67.65.177]6 167 ms 167 ms 167 ms xe-5-1-0.sjc10.ip4.tinet.net [89.149.185.161]7 390 ms 388 ms 388 ms as4837.ip4.tinet.net [77.67.79.150]8 397 ms 393 ms 397 ms 219.158.30.419 892 ms * 392 ms 219.158.97.1310 407 ms 403 ms 403 ms 219.158.11.19711 452 ms 451 ms 452 ms 219.158.15.512 * 434 ms 434 ms 123.126.0.6613 449 ms 450 ms 450 ms 61.148.3.3414 432 ms 433 ms 431 ms 202.106.43.6615 435 ms 435 ms 436 ms 123.125.114.144While detailed information about Chinese ISPs is limited, we have identified Tinet as a key player. Their website provides a visual representation of their network connections:
Tinet employs a distributed network of hops to ensure reliability, mitigating the impact of potential outages. Repeating this process multiple times can provide a broader understanding of the overall network connectivity.
Defining Network Tiers
The extensive networks discovered through tracerouting are categorized as Tier 1 networks.
Although no official body defines network tiers within the Internet, a common definition of a Tier 1 network is one capable of reaching all other networks on the Internet without purchasing IP transit or paying settlement fees.
By this definition, a Tier 1 network is transit-free and peers with every other Tier 1 network. However, not all transit-free networks qualify as Tier 1. Achieving transit-free status through paid peering or settlement agreements is possible.
Common definitions for Tier 2 and Tier 3 networks exist:
The Internet Backbone page provides a list of current Tier 1 networks. It is uncertain whether AOL Transit Data Network (ATDN) remains a Tier 1 network.
Understanding Peering
These networks connect through a process called 'peering'. Most internet traffic traverses at least two different top-tier networks to reach its destination, and these networks are interconnected through peering arrangements. Typically, each party agrees to route a specific amount of traffic for the other, and vice versa.
Financial transactions are usually absent in these arrangements, unless one side significantly outweighs the other in data exchange. Large companies can also establish their own peering relationships. For example, Netflix has created its own peering and network infrastructure directly with multiple Tier 1 networks to reduce costs and improve proximity to end-users on major US broadband ISPs.
Further information on peering can be found on this Wikipedia page.
This explanation provides a general overview; further investigation is encouraged for a comprehensive understanding.
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