Tier 1, Tier 2 & Tier 3 Internet Service Providers


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:

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:

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:

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:

Got questions? Leave a comment! Let’s chat.

Rafay Rasool is a Network Specialist with over 10 years of experience designing, configuring and implementing core network solutions based predominantly but not limited to Juniper Routers, Switches and Firewalls along with other vendors such as Cisco, Huawei, Siemens, Aerohive, Ringmaster, Pulse etc for Internet Service Provider and Enterprise Networks.

Rafay is an avid supporter of network automation and likes to code and automate networking solutions.