====== IP addresses ======

IP address is the device's unique identifier in the [[network|network]]. It works on 3rd layer of [[osi_model|OSI]], [[network-layer_network|The Network layer]]. It uses Best-effort delivery, meaning it has no guarantee data won't be lost on the way, which is mitigated by [[network-layer_transport|The Transport layer]] protocols.

It has two common standards: IPv4 and IPv6.

==== IPv4 ====

{{ :ipv4_address_structure_and_writing_systems-en.svg |}}

IPv4 addresses can be represented in any notation by 32-bit number.

IP addresses can be public and private. Private IP addresses:
  * 10.0.0.0/8
  * 172.16.0.0/12
  * 192.168.0.0/16

There's other reserved ranges:
  * 0.0.0.0/8 - current network
  * 100.64.0.0/10 - shared address space used by ISPs
  * 127.0.0.0/8 - loopback interface
  * 169.254.0.0/16 - link-local addresses (for when IP is not specified, like when retrieving it from a DHCP server)
  * 192.88.99.0/24 - formerly used for IPv6 to IPv4 relay
  * 255.255.255.255/32 - limited broadcast
  * ...and so on.

==== IPv6 ====

{{ :ipv6_address_terminology-en.svg |}}

IPv6 was intended to replace IPv4. It uses 128-bit addresses. Direct communication between IPv6 and IPv4 is impossible, though there are some transition mechanism to help with that.

IPv6 simplifies many aspects, so it's faster than IPv4.