How it works
The internet is a network of networks that relies on addressing, routing, packets, DNS, and protocols.
Separate domain names, IP addresses, packets, routing, and application protocols when reading a scenario.
Common error
A domain name is not the same thing as an IP address, and DNS does not deliver the whole web page.
Worked example
Explain the roles in a browser request without assigning all delivery to DNS.
Data / pseudocode
Name lookup -> destination address
Routing -> next-hop decisions
Packets -> pieces of transmitted data
Application -> requested web contentDNS resolves a name, while packet forwarding carries traffic across networks toward a destination address. The application exchanges the requested content using its communication protocols. DNS can succeed even when the destination service is unavailable.
Exercises
4.1.1
Can a successful DNS lookup prove a website is online and responding? Explain.
Show solution
No. It establishes a name-resolution result. The route, server, application, or service policy may still prevent a successful request.
4.1.2
Distinguish the internet from the World Wide Web.
Show solution
The internet is interconnected network infrastructure and protocols. The web is an application system of linked resources accessed through web protocols over that infrastructure.