In computing, ahextet, or achomp, is a sixteen-bit aggregation,[1][2] or fournibbles. As a nibble typically is notated in hexadecimal format, a hextet consists of 4 hexadecimal digits. A hextet is the unofficial name for each of the 8 blocks in anIPv6 address.
A hextet is also referred to as asegment, in some documentation.[3]
Bob Bemer suggested the use of hextet for 16-bit groups in 2000.[1] In 2011 anInternet Draft explored various alternatives for hextet such asquibble, short for "quad nibble".[2] In response to this draft, author Trefor Davies suggested the use of the wordchomp because it is in line with the current denominationsbit,nibble,byte.[4]
Hextet would more properly describe a 6-bit aggregation, whereas the exact term for 16 bits should behexadectet, directly related to the termoctet (for 8 bits). However, because it is harder to pronounce, the short formhextet is used—in analogy to howhex is commonly used as an abbreviation forhexadecimal in computing. This usage ofhex to mean 16 is also in line with the similarIEEE 1754 termhexlet indicating 16 octets.[5]
Although the wordhextet is not officially recognized in theIETF documents, the word is used in technical literature on IPv6[6][7] published after the Internet Draft. Official IETF documents simply refer to them aspieces.[8]
Cisco sources generally[citation needed] use the termquartet as does IPv6.com,[9] a reference either to the four digit grouping or to the fact that it represents four nibbles; however, this term is also used by some to refer to a four-bit aggregation.[10][11]
[…] I came to work forIBM, and saw all the confusion caused by the 64-character limitation. Especially when we started to think about word processing, which would require both upper and lower case. […] I even made a proposal (in view ofSTRETCH, the very first computer I know of with an 8-bit byte) that would extend the number ofpunch card character codes to 256 […]. So some folks started thinking about 7-bit characters, but this was ridiculous. With IBM's STRETCH computer as background, handling 64-character words divisible into groups of 8 (I designed the character set for it, under the guidance of Dr.Werner Buchholz, the man who DID coin the term "byte" for an 8-bit grouping). […] It seemed reasonable to make a universal 8-bit character set, handling up to 256. In those days my mantra was "powers of 2 are magic". And so the group I headed developed and justified such a proposal […] TheIBM 360 used 8-bit characters, although not ASCII directly. Thus Buchholz's "byte" caught on everywhere. I myself did not like the name for many reasons. The design had 8 bits moving around in parallel. But then came a new IBM part, with 9 bits for self-checking, both inside the CPU and in thetape drives. I exposed this 9-bit byte to the press in 1973. But long before that, when I headed software operations forCie. Bull in France in 1965-66, I insisted that "byte" be deprecated in favor of "octet". […] It is justified by new communications methods that can carry 16, 32, 64, and even 128 bits in parallel. But some foolish people now refer to a "16-bit byte" because of this parallel transfer, which is visible in theUNICODE set. I'm not sure, but maybe this should be called a "hextet". […]
The Timico engineering team has started to use the word "chomp" to represent two bytes or the 4 Hex character block in IPv6. Chomp is clearly in the mould of bit, nibble and byte and I would be grateful if you could chew this one over with a view to supporting the idea – we are submitting it as a suggestion when the above Draft expires.
The preferred form is x:x:x:x:x:x:x:x, where the 'x's are the hexadecimal values of the eight 16-bit pieces of the address
IPv6 addresses are denoted by eight groups of hexadecimal quartets separated by colons in between them.
A data symbol represents one quartet (4 bits) of binary data.