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Structure of the Internet and Internet Communication

The Internet

The internet is a network of networks set up to allow computers to communicate with each other globally. It is accessed via Internet Service Providers (ISPs), which usually provide routers for families and businesses to access the internet.

URLs

URLs are made up of:

  • Method (http://, https://, etc)
  • Host (www, mail, etc)
  • Domain name (google, microsoft, etc)
  • Second level domain (co, org, etc) (not always necessary) (there can be more levels, but this is uncommon)
  • Top level domain (uk, ps, etc) (necessary)
  • Location (e.g. webpage.html)
  • Resource (e.g. #element)

https://www.domainname.com/folder/subfolder/webpage.html#element

Domain names identify the areas or domains that internet resources reside in. Thees are structured into a hierarchy of smaller domains and written as strings separated by full stops as dictated by the rules of the Domain Name System (DNS).

Internet registrars hold records of all existing website names and details of domains that are available for sale. They resell domain names.

Internet registries own worldwide databases that hold records of all domain names currently issued to individuals and companies with their details. They also allocate IP addresses and keep track of which address(es) a domain name is associated with as part of the DNS.

Domain Name System

The Domain Name System (DNS) is a "hierarchical and distributed name service that provides a naming system for computers, services, and other resources on the Internet or other Internet Protocol networks" (source).

Domain names are made up of:

  • A website name.
  • Company second level domain (2LD) (not always necessary) (there can be more levels, but this is uncommon)
  • Company top level domain (TLD).

To be a fully qualified domain name (FQDN), there must also be a host.

  • Host (e.g. www, mail)

https://www.bhf.org.uk

https://www.bookstack.asadhussain.net

IP Addresses

An Internet Protocol (IP) address is a unique address that is assigned to a network device. It indicates where a packet of data is to be sent or has been sent from. Routers use the IP address to direct data packets accordingly.

Networks

  • A Local Area Network (LAN) consists of multiple devices connected over a small geographical area. Companies/individuals own and use their own hardware for a LAN, e.g. copper cables and ISP routers.
  • A Wide Area Network (WAN) consists of multiple LANs connected over a large geographical area. Usually used by companies, this type of network usually requires renting infrastructure to connect LANs.

Network Topologies for LANs

Topology Description Advantages Disadvantages
(1) Physical bus All devices are connected to a single cable.

Inexpensive to set up due to not a lot of cables required.

Single point of failure (main wire).

With more traffic, performance degrades due to data collisions.

Since every device has access to the cable, there is low security as all traffic can be seen.
(2) Star All devices are connected to a central node, usually a switch, which routes data.

If one cable fails, other devices can still connect.

Consistent performance, even under high load.

No problems with data collisions.

The system is more secure due to only one path between a device and the switch.

Easy to add nodes to the network.

Costly due to more cables required.

Single point of failure (central node).
(3) Partial/Full mesh All devices are connected to each other, and access each other via these connections.

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