internet

• IP address


  A unique numerical address used to identify a host computer or network node trying to communicate over IP on the Internet
• Network identifier


  The part of an IP address that identifies the specific network
• Host identifier


  The part of an IP address that identifies the specific host within the network
• Subnet mask


  Used to identify the network identifier part of the IP address
• Standards of IP address

  • IPv4
  • IPv6
• IPv6 offers 340 trillion, trillion, trillion unique addresses
• IPv4 addresses consist of a 32-bit number written in a dotted-decimal notation
• Some IP addresses cannot be used for an individual network or host
• Reserved IP addresses


  Addresses that cannot be used for an individual network or host
• Private, non-routable addresses


  127.x.x.x used for diagnostics within local networks only
• Broadcast address

  x.x.x.255
• Default router address

  X.X.X.1
• Classful addressing


  A system used to define the size or proportion of the network and host identifiers within a 32-bit IP address
• Classless addressing


  A modern system that specifies the number of bits in the subnet mask
• Subnetting


  A technique used to create subnetwork segments within a larger IP network
• Subnetting reduces the size of the broadcast domain which can improve security, speed and reliability
• Subnet ID


  Created by using the most significant bits from the host ID section of the IP addresses
• Public IP address


  Must be globally unique and can be addressed directly by any other computer in the world
• Private IP address


  Unique within their local network and do not require registration with an Internet registry
• Dynamic Host Configuration Protocol (DHCP)

  A system used to automatically assign dynamic IP addresses to computers on a network
• DHCP process

  1. DHCPDISCOVER

  2. DHCPOFFER

  3. DHCPREQUEST

  4. DHCPACK
• Network Address Translation (NAT)

  Used to convert IP addresses as they pass between a public address space and a private address space
• Port forwarding

  A product of NAT that forwards incoming requests to a particular IP address and port within a private network
• Static IP addressing is uncommon as it permanently allocates a networked computer a scarce IPv4 address
• DHCP provides the subnet mask and other automatic configuration details alongside the IP address
• Private addresses are not routable and cannot be used for routing packets on the Internet
• NAT provides a solution to the lack of public address in IPv4 while transitioning to IPv6
• NAT offers an additional layer of security by automatically creating a firewall between the internal and external networks
• Subnet mask of 255.255.255.0 indicates that 24 bits have been used for the network ID
• Subnetting allows two computers in different subnetworks to communicate simultaneously without collisions
• The Internet is a network of networks set up to allow computers to communicate with each other globally
• The World Wide Web (WWW) is a collection of web pages that reside on computers connected to the Internet
• World Wide Web (WWW)


  A collection of web pages that reside on computers connected to the Internet
• The Internet is frequently used without using the WWW
• Uniform Resource Locator (URL)


  The full address for an Internet resource
• URL components

  • Method
  • Host
  • Location
  • Resource
• Internet registrars are needed to ensure that a particular domain name is only used by one organisation
• Internet registrars hold records of all existing website names and the details of those domains that are currently available to purchase
• All registrars must be accredited by their governing registry
• Internet registries are five global organisations governed by ICANN