There are several ways to view the internet.

“Nuts and Bolts" View

• Internet consists of billions of connected computing devices
  • hosts = end systems
  • we run network apps at the Internet’s “edge”
• Packet switches within the internet forward packets (chunks of data)
  • physically, packet switches interconnect any system to a host
  • packet switches include routers and switches
• Communication links (e.g. fiber, copper, radio, satellite) allow for connection between multiple devices
  • Transmission rate is the bandwidth, i.e. the rate at which you can push bits on a medium
• Networks are collection of devices, routers, and links which are managed by an organization

Services View

• Internet can also be viewed as infrastructure that provides a “transport” service to applications
  • Services include web, video streaming, multimedia teleconferencing, email, games, e-commerce, social media, etc.
  • We have “hooks” which allow sending/receiving apps to “connect” using Internet transport service
  • Different transport service options are available (e.g. Skype, HTTP, etc.)

“Network of Networks” View

• Hosts connect to the Internet via an access network
• Access networks in turn must be interconnected - this allows two hosts to send packets to each other from any location
• Result is a very complex network of networks - evolution driven by economics, national policies

There are several key components in the structure of the Internet:

• Network Edge
  • Consists of hosts (clients or servers)
  • Note that servers are often located in data centers
• Access Networks

  • e.g.

    • Residential access networks (home)

    

    • Institutional access networks (enterprise, university, etc.)

      • Between switches, a higher transmission rate is needed due to traffic (aggregation of traffic)
      • e.g. Different ISPs for one campus - don’t have single point of failure for outage, different deals with different providers

      

      • Mix of wired + wireless link technologies
      • Connects a mix of switches and routers
      • e.g. Ethernet provides wired access at 100 MB/s, 1GB/s, 10GB/s
      • e.g. WiFi provided wireless access points at 11, 54, 450 MB/s

    • Mobile access networks (WiFi, 4G/5G)

    • Data center network

      • High-bandwidth links (10s-100s GB/S) connect hundreds to thousands of servers together and to the internet