The Internet from 100,000 feet
The Internet is a network of networks connected in a mesh. It also has a distinct hierarchy of connectivity, which is best illustrated by the image below.
At the very edge of the Internet are the users. They are the consumers in their homes, or on their mobile networks, and businesses and business users who use the Internet for communication, entertainment, and commerce.
Tier 3 Networks provide Internet access to users through one or more connections to a Tier 2 Network. Examples of Tier 3 Networks are small regional ISPs, small mobile providers, and university networks.
Tier 2 Networks provide Internet access to users and Tier 3 Networks through one or more peering connections with other Tier 2 Networks and one or more connections to a Tier 1 Network. Examples of Tier 2 Networks are major cable, DSL, and mobile providers.
Tier 1 Networks are global networks that provide Internet access to Tier 1 and Tier 2 Networks (and occasionally to users). Tier 1 Networks peer with each other using reciprocal agreements whereby two Tier 1 Networks do not charge each other for access to their networks. Tier 2 Networks and users will be charged for access to a Tier 1 Network. There are slightly more than a handful of Tier 1 Networks in the world.
Akamai’s position in the Internet
Akamai places its servers as close to the users as possible - in Tier 3 Networks. But in order to reach into Tier 3 Networks, where relationships have yet to be established, and to enable the tiered distribution, performance, and fault tolerant models, servers are placed in IXC, Tier 2, and Tier 1 Networks.
Akamai edge servers have short last-mile distances from our servers to the users, as well as having options for intermediate hops between these edge deployments and the origin servers where the content is published.
How this affects object delivery
The methods by which a user connects to our network and retrieves content is described in the Akamai Delivery Overview document.
When an Akamai edge server gets a request for an object, the customer’s configuration data defines which features to apply to that request and how the request should go forward to the origin to retrieve objects that are not in cache.
A direct path would tell the edge server to connect directly to the origin and would provide the least traffic offload, performance, and fault tolerance of the options.
Tiered distribution adds a layer of fan out which improves traffic offload from the origin and improves performance through the added layer of caching and shorter retransmission distances.
Akamai’s SureRoute technology enables edge servers to select the best path between the edge and the origin by choosing one or more intermediate hops which can be at any of over 2,200 deployments around the world, or by going direct to the origin if that path is determined to be the best choice. Real time races along these paths are continually run in order to select the best path in the dynamically changing environment that is the Internet.