A network of networks
There is no single owner of the Internet.
The Internet is made of many independently operated networks. A home or campus network connects to an access provider; that provider can exchange traffic with other providers or reach them through transit networks.
Routers move packets between networks one hop at a time. Networks share reachability information so routers can choose useful next hops, but no single router needs a complete map of every path.
Build the model
Four roles along the way
Local network
Connects nearby devices and sends off-network traffic to a router.
Access provider
Connects a customer network to destinations beyond its local link.
Transit provider
Carries traffic between networks that do not connect directly.
Interconnection
Lets independent networks exchange traffic and reachability information.
Mini experiment
Follow an interconnection
Select a relationship to see how it helps traffic move beyond one local network.
An access provider connects the customer network to destinations beyond its local link.
The customer sends remote traffic to its local router first.
Knowledge check
Test your Internet model
Answer five questions. The answer order changes each time.