Ever wondered how effortless it seems when you communicate over the internet. Everything seems to be always available, always on. Most of the time, it is a simple case of connecting to your home wifi router and off you go. Things aren’t as simple behind the scenes though. There is a huge mesh of inter-connectivity between networks at a global scale that allows us to communicate. This inter-connectivity is largely possible due to the flow of traffic between tier 1, tier 2 and tier 3 internet service providers (ISPs).
Tier 1 ISPs provide the backbone of connectivity for all internet on a global scale. Tier 1 ISPs interconnect with each other to share big data channels for traffic to pass through them. They usually peer directly with each other with each tier 1 provider responsible for a large chunk of global traffic. Tier 1 providers don’t purchase transit links as they form the backbone of the internet which other networks utilise as their transit.
Tier 2 ISPs provide connectivity between tier 1 and tier 3 ISPs. They purchase transit links from tier 1 providers and freely peer with other tier 3 ISPs and any other enterprise that wishes to peer with them. Selling a middleman service, the goal of tier 2 providers is to have as many networks connected as possible. This enables them to provide lower latency to their customers.
Tier 3 ISPs fall in the realm of the end user. These ISPs are largely responsible for connectivity on the last mile. Tier 3 ISPs connect home users with a network and via their links with tier 2 and tier 1 providers, tier 3 providers inject meaningful traffic into the internet. This traffic than makes its way via tier 1 provider’s backbone network all the way to the destination which usually sits inside a tier 3 ISP network or a non-ISP network connected to a tier 2 ISP. A tier 3 ISP can have direct links with a tier 1 ISPs.
To understand the end to end packet flow over the internet, please refer to my video below:
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