What is an IP-address?

IP-address (Internet Protocol Address) — is a unique identifier (address) of a device (PC, laptop, mobile phone, printer, router, etc.), connected to the Internet.

Each device on the Internet has its own IP-address. Since you are currently connected to the Internet - it means that your computer also has its own unique address on the network. But you can be connected to the Internet through a router or gateway in your local network. In this case, your computer from the Internet isible with the same IP address, which has your router or gateway.

IP addresses can be static (when provider assigned a permanent address to the user), and dynamic (if the provider gives you the IP address from the pool of free addresses on DHCP when you are connecting).

In addition, built on the basis of virtual hosts computer can act as multiple devices with the multiple IP addresses. For example, web hosting services on the Internet.

Knowledge of your IP address allows to provide you access to services and programs on your computer (games, chat rooms, FTP, remote access to desktop, etc.)

There are two types of IP-addresses - IPv4 and IPv6.

The main difference from the usual IPv4 to IPv6 is a significant increase of address space. Thus, the length of the IPv4 addresses are 32 bits, which gives a total of 232 of possible addresses (just over 4 billion addresses). At the same time, length of an IPv6 address is 128 bits, which gives 2128 of possible addresses (generally is more than 4.8×1028 addresses for each of the 7 billion people on Earth). That is, IPv6 once and forever solve the problem of exhausting of Internet address space.

In terms of syntax, writing both IPv4 and IPv6 addresses are also different. IPv4 addresses are written as four blocks of numbers from 0 to 255 separated by dots, e.g. 192.168.254.123. IPv6 addresses are written as eight blocks of hexadecimal digits separated by colons, such as fe80:dead:beef:0:0:0:0:2012. Often, writing IPv6 addresses can be simplified by replacing the sequence of zeros with the double colon (but this can be done only at one place). So the address shown in the previous example can be written as fe80:dead:beef::2012.

There are also many differences at the protocols level of IPv4 and IPv6, but for the end Internet-user it is a negligible value. However, for anyone interested, we present a short comparison of the differences in protocols below.

IPv4 IPv6
Addresses are 32 bits (4 bytes) in length Addresses are 128 bits (16 bytes) in length
Address (A) resource records in DNS to map host names to IPv4 addresses Address (AAAA) resource records in DNS to map host names to IPv6 addresses
Pointer (PTR) resource records in the IN-ADDR.ARPA DNS domain to map IPv4 addresses to host names Pointer (PTR) resource records in the IP6.ARPA DNS domain to map IPv6 addresses to host names
IPSec is optional and should be supported externally IPSec support is not optional
Header does not identify packet flow for QoS handling by routers Header contains Traffic Class field, which identifies packet flow priority for QoS handling by router
Both routers and the sending host fragment packets Routers do not support packet fragmentation. Sending host fragments packets
Header includes a checksum Header does not include a checksum
Header includes options Optional data is supported as extension headers
ARP uses broadcast ARP request to resolve IP to MAC/Hardware address Multicast Neighbor Solicitation messages resolve IP addresses to MAC addresses
Internet Group Management Protocol (IGMP) manages membership in local subnet groups Multicast Listener Discovery (MLD) messages manage membership in local subnet groups
Broadcast addresses are used to send traffic to all nodes on a subnet IPv6 uses a link-local scope all-nodes multicast address
Configured either manually or through DHCP Does not require manual configuration or DHCP
Must support a 576-byte packet size (possibly fragmented) Must support a 1280-byte packet size (without fragmentation)
Used TTL (Time to Live) header field for packets TTL renamed to Hop Limit
Header size is 20 bytes Header size is 40 bytes
Max packet size is 65535 bytes (216 - 1) Supporting jumbograms - huge packets up to 4 Gb (4294967295 = 232 - 1)

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