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Internet Protocol version 4 (IPv4) was the first standalone specification for the IP address, and has been in use since 1983. [2] IPv4 addresses are defined as a 32-bit number, which became too small to provide enough addresses as the internet grew, leading to IPv4 address exhaustion over the 2010s.
The IP address of the destination is used to make decisions about routing IP packets to other networks. IPv6 is the successor to the first addressing infrastructure of the Internet, Internet Protocol version 4 (IPv4). In contrast to IPv4, which defined an IP address as a 32-bit value, IPv6 addresses have a size of 128 bits.
The IHL field contains the size of the IPv4 header; it has 4 bits that specify the number of 32-bit words in the header. The minimum value for this field is 5, [33] which indicates a length of 5 × 32 bits = 160 bits = 20 bytes. As a 4-bit field, the maximum value is 15; this means that the maximum size of the IPv4 header is 15 × 32 bits = 480 ...
The prefix length can range from 0 to 128, due to the larger number of bits in the address. However, by convention, a subnet on broadcast MAC layer networks always has 64-bit host identifiers. [13] Larger prefixes (/127) are only used on some point-to-point links between routers, for security and policy reasons. [14]
Packets that hold Internet Protocol data carry a 4-bit IP version number as the first field of its header. [ 1 ] [ 2 ] Currently, only IPv4 and IPv6 packets are seen on the Internet , having IP version numbers 4 and 6, respectively.
Unicast address assignments by a local Internet registry for IPv6 have at least a 64-bit routing prefix, yielding the smallest subnet size available in IPv6 (also 64 bits). With such an assignment it is possible to embed the unicast address prefix into the IPv6 multicast address format, while still providing a 32-bit block, the least ...
The checksum field is the 16 bit one's complement of the one's complement sum of all 16 bit words in the header. For purposes of computing the checksum, the value of the checksum field is zero. If there is no corruption, the result of summing the entire IP header, including checksum, and then taking its one's complement should be zero.
Using octets with all eight bits set, the representation of the highest-numbered IPv4 address is 255.255.255.255. An IPv6 address consists of sixteen octets, displayed in hexadecimal representation (two hexits per octet), using a colon character (:) after each pair of octets (16 bits are also known as hextet ) for readability, such as 2001:0db8 ...