Subject: IPv6 terminology question

From: Daniel Stickney <[email-masked]>
Date: Fri, 07 Aug 2009 12:24:43 -0600

Hello all,
        
I am searching for an authoritative answer to my question on IPv6
terminology. I hope this is an appropriate list to ask on, and if it is
not I sincerely apologize. So far in my searching I have mostly been
finding inconsistency, confusion and guessing. I would like to know if
there is an official term for the colon separated 16-bit groups in an
IPv6 address. I'm asking here because I believe an answer from members
of the IETF is as official as it gets. 
        
Personally I've been calling them "words"; as in "an IPv6 address is
made up of 8 colon separated words."  I see the term "word" used in some
other whitepapers and documents published about IPv6 (The TCP/IP Guide,
ISBN-13: 9781593270476, p. 379, and also
http://documents.iss.net/whitepapers/IPv6.pdf). I also see the term
"octet" used, but I believe incorrectly since only an IPv4 address is
four 8-bit groups, or octets. I've seen "quartet", "pieces" and "quad"
used, and heard guesses at "hexadecitet", "double-octet" and many
others.

I'm starting to discuss IPv6 in a professional environment with other
network engineers and I want to make sure I'm using proper terminology
during discussions and for documentation. Plus all the people who I've
seen asking this same question can reference this thread for an answer
themselves.

Thanks in advance for your time,

-- 
Daniel Stickney
Operations Manager - Systems and Network Engineer

---

From: Daniel Stickney <[email-masked]>
Date: Fri, 07 Aug 2009 13:32:52 -0600

> Daniel,
> 
> This is defined in RFC4291 "IPv6 Addressing Architecture" Section 2.2 "Text Representation of Addresses".  It says:
> 
>    1. The preferred form is x:x:x:x:x:x:x:x, where the 'x's are one to
>       four hexadecimal digits of the eight 16-bit pieces of the address.
>       Examples:
> 
>          ABCD:EF01:2345:6789:ABCD:EF01:2345:6789
> 
>          2001:DB8:0:0:8:800:200C:417A
> 
>       Note that it is not necessary to write the leading zeros in an
>       individual field, but there must be at least one numeral in every
>       field (except for the case described in 2.).
> 
> The closest thing to a definition would be to call them "field"s.  For example, "an IPv6 address is made up of 8 colon separated fields".
> 
> Bob
> 
> p.s. Suggest in the future, try reading the actual specifications.  
> 

I appreciate your input Bob.

What term do you all normally use in your discussions with other
engineers? I'm fine with "field", just haven't heard or seen anyone else
use it yet.

Thanks,

p.s. I did read that spec, and several others. In my first message when
I said 'I've seen "quartet", "pieces" ....', that term "pieces" comes
from the 2nd line of the section you quoted. I just thought "pieces" and
"field" were generic enough to not be official terms.

---

From: Joel Jaeggli <[email-masked]>
Date: Fri, 07 Aug 2009 13:31:42 -0700

> engineers? I'm fine with "field", just haven't heard or seen anyone else

A book that I performed a review on covering this subject states:

"IPv6 addresses are written in 8 groups of 16 bits each, or 8 groups of
4 hexadecimal numbers separated by colons." - Goralski, "The Illustrated
Network" 2009

I'm comfortable with that being sufficiently unambiguous, modula you
have to skip to the next paragraph to get abbreviation.

---

From: "Dunn, Jeffrey H." <[email-masked]>
Date: Fri, 7 Aug 2009 18:27:52 -0400

Colleagues,

From an applications programming viewpoint, the 2 octets between the colons are called an unsigned short, as in the 16-bit C language data structure. RFC 3493 specifies the IPv6 address structure as 16 unsigned 8-bit integers; however, this is functionally equivalent to 8 unsigned 16-bit integers. As a result, the x's in the message below are unsigned shorts.

Best Regards, 
  
Jeffrey Dunn 
Info Systems Eng., Lead 
MITRE Corporation.
(301) 448-6965 (mobile)

---

From: Brian E Carpenter <[email-masked]>
Date: Sat, 08 Aug 2009 13:19:50 +1200

I don't see why C terminology wins, especially in a reference back to
traditional mini-computer architectures. For example, in the most accurate
ABNF we have for the presentation format, they're called "hex4"
(draft-ietf-sip-ipv6-abnf-fix).

As Bob said, they're generically called "fields" in the defining
RFC, which seems fine to me.

    Brian

---

From: Matt Anderson <[email-masked]>
Date: Mon, 10 Aug 2009 15:13:09 -0400

I find the word "field" too generic, just like "parts" and "sections."

In IPv4, we call them "octets," because each is 8 bits wide.  In IPv6,
I've always thought of them as "hextets," because each is 16 bits
wide.  "Hextet" may also remind novices that they are working in
hexadecimal, not base-10 like they're used to with IPv4.

A quick Google search will reveal a number of places where the word
"hextet" is used ("hextet ipv6" has 800+ results).

I think that most people familiar with IPv6 would understand what
"hextet" means, in this context, even if they hadn't heard the word
before.

---

From: Jeroen Massar <[email-masked]>
Date: Mon, 10 Aug 2009 21:40:16 +0200

> of the IETF is as official as it gets. 
[..]

QUAD

That is nothing "official", but that is how I tend to call it.
"An IPv6 address contains 8 quads".

There are 4 (quad) nibbles (4 bits) making up the 16-bit groups, 8 of
which make 128bits.

I don't recall where I got that from, but then again over the years I
probably have read way too much IPv6 material. Possibly derived from the
quad-A (AAAA) record. googling a bit, it seems I am not the only person
doing that: http://www.potaroo.net/ispcol/2008-08/ipv6addr.pl

Geoff, where did you get this from? :)
(As I would not be surprised that I picked it up in one of his many
interesting publications ;)

Greets,
 Jeroen

---

From: Geoff Huston <[email-masked]>
Date: Tue, 11 Aug 2009 06:39:56 +1000

> interesting publications ;)

I think I picked it up from the quad-A terminology. I don't recall any  
other term
that has been commonly used to described the IPv6 address notation.

    Geoff

---

From: Seiichi Kawamura <[email-masked]>
Date: Tue, 11 Aug 2009 11:29:56 +0900

Hi

I think fields is fine. That's what we call it in our ISP.
I know some others that do. Quads sound nice too.
I just got used to what I saw in RFC4291.

Regards,
Seiichi

>> have to skip to the next paragraph to get abbreviation.

- --
================================================
NEC BIGLOBE Ltd.
   Seiichi Kawamura <[email-masked]>
   +81 3 3798 6085  (FAX: +81 3 3798 6029)
   +81 90 1547 4791 (mobile)

---

From: Russell Heilling <[email-masked]>
Date: Tue, 11 Aug 2009 09:10:49 +0100

> I find the word "field" too generic, just like "parts" and "sections."

Personally I find 'field' or '16-bit field' to be preferable.

> hexadecimal, not base-10 like they're used to with IPv4.

Actually a 'hextet' would be 6 bits.  A 16-bit value would be a
'hexadecatet' which doesn't flow off the tongue quite so well...

-- 
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