Applying Computers

Chapters 5

Principles of network connectivity

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Tags: Using computers for personal needs

Connectivity between computers is possible by means of network protocols.

Large blocks of data are not transmitted as a continuous stream. Using information exchange protocols, they are divided into smaller parts (packets) for transport, and after successful receipt on the target device they are reassembled into the original form.

Similar to the real world, addresses are used for navigation, and specialized network computers are responsible for correct delivery of data between them.

Addressing standards

Every device on the network needs a unique IP address. Today there are two main standards:

  • IPv4: ~4,294,967,296 addresses
  • IPv6: ~340,282,366,920,938,463,463,374,607,431,768,211,456 addresses

Such a number of addresses (especially in IPv6) makes it possible to create networks of any scale.

Subnets are dedicated address blocks administered by network computers.

  • Local subnets operate in reserved private address blocks that by standard cannot be used for global addressing. Examples for IPv4:
    • 10.0.0.0/8 (16,777,216 addresses)
    • 172.16.0.0/12 (1,048,576 addresses)
    • 192.168.0.0/16 (65,536 addresses)
    • 127.0.0.0/8
    • 169.254.0.0/16
  • External subnets operate with global, non-reserved addresses and, with correct connectivity, can be reachable from the global Internet.

Typical example: Internet provider and home router

An Internet provider administers a network computer that maintains connectivity with the global Internet. To provide connectivity services to the client, a physical connection is made from the provider’s network computer to the client’s network computer.

When connecting the client’s network computer, a private or public address is configured at the level of the provider’s network computer. This address is used for addressing the client’s traffic to the global network, tracking traffic, and collecting the subscription fee.

The client’s network computer administers its own private subnet and is responsible for addressing traffic from it to the provider’s network computer. Configuration is usually done through a web interface or manufacturer programs.

  • The provider connects to the WAN (external) port of the client device — typically blue; used by default for routing to global resources.
  • The user’s private computers connect to LAN ports — typically yellow — or via radio waves (Wi-Fi). Without additional configuration, devices on the private subnet have direct connectivity with one another.

Typical network functions

  • Routing — providing connectivity between computers by assigned IP addresses. If connectivity is lost along one route, the system can automatically choose another path.
  • DNS (Domain Name System) — translates machine IP addresses into a human-readable text format. Thanks to DNS you remember google.com, not a numeric address such as 8.8.8.8.
  • DHCP (Dynamic Host Configuration Protocol) — automatically issues IP addresses to new devices connecting to the network, relieving the user of the need to configure them manually.