The Internet

Composition

There are 4 tiers in the composition of the internet

  1. Tier-1 ISPs
    • Top level of the routing hierarchy
    • Large telecommunications companies exchange traffic directly with each other via peering agreements
  2. Tier-2 ISPs
    • Buy Internet transit from Tier-1 providers to reach some on the global Internet
    • Also engage in peering
    • May use a single T1 provider for connectivity, or implement multihoming to achieve redundancy and load balancing
  3. Access ISP
    • Provides Internet connectivity to end users
    • Via DSL, cable, wireless etc.

World Wide Web

Parts of a URL

http:// website.com /path/to/directory/ document.html
Protocol

Name of the host holding the document.

Can also be an IP address

Directory Path Document Name

Hypertext Document

Encoded as a text file and uses tags to build the structure of a web page for a web browser to render. They are often paired with CSS documents to describe how the page should be styled.

Rich Internet Application - RIA

A web application designed to deliver the same features and functions normally associated with desktop applications. They generally split processing by locating the user interface and related activities on the client side, and data manipulation and operations on the application server side.

Application Server

A server program in a computer in a distributed network that provides the business logic for an application.

Frequently viewed as part of a three-tier application consisting of:

  • A graphical user interface (GUI) server
  • An application (business logic) server
  • A database and transaction server
  • A first-tier, front end, web browser based GUI
  • A middle-tier business logic application, or set of applications possibly on a LAN or internet server
  • A third-tier, back end database and transaction server, sometimes on a mainframe or other large server

Mobile Apps

A computer program designed to run on mobile devices. Native apps run directly on the phone rather than indirectly through a web app on a web browser.