[138933] in North American Network Operators' Group
Re: Creating an IPv6 addressing plan for end users
daemon@ATHENA.MIT.EDU (Owen DeLong)
Thu Mar 24 09:48:12 2011
From: Owen DeLong <owen@delong.com>
In-Reply-To: <BE6C0A99-000E-4DF6-8804-0DB8E91C95C6@ripe.net>
Date: Thu, 24 Mar 2011 06:45:15 -0700
To: Nathalie Trenaman <nathalie@ripe.net>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Mar 24, 2011, at 1:06 AM, Nathalie Trenaman wrote:
> Hi Liudvikas,
>=20
> Thank you very much for your feedback.=20
>=20
> On Mar 23, 2011, at 4:56 PM, Liudvikas Bukys wrote:
>=20
>> Hi, I saw your document "Preparing an IPv6 Addressing Plan" after its =
URL was posted to NANOG.
>>=20
>> I have one small comment that perhaps you would consider in future =
revisions:
>>=20
>> The use of decimal numbers coded in hexadecimal is introduced in =
section 3.2, "Direct Link Between IPv4 and IPv6 Addresses", without =
discussion. It's also implicit in section 4.9 when encoding decimal =
VLAN numbers in hexadecimal address ranges.
>>=20
>> My opinion is that this may be a source of confusion, and should be =
explicitly described somewhere before section 3.2, as a deliberate =
implementation choice that makes it easier for human operators to =
configure and recognize deliberately-chosen mappings between decimals in =
IPv4 addresses and integers and corresponding fields in hexadecimal =
address ranges.
>=20
> You are right, we could explain this section in more detail and we =
have received this feedback from some other readers as well. We will =
take this into account for future revision.=20
>=20
>>=20
>> Without an explicit discussion, this point may be missed by some =
readers -- especially since this is a training document.
>>=20
>> Just my opinion!
>>=20
>> I'm also curious as to whether this describes the way the world has =
already settled on, or whether this is a novel, controversial, or =
only-occasonally-observed technique. I see that RFC 5963 - IPv6 =
Deployment in Internet Exchange Points (IXPs) of August 2010 does =
mention BCD encoding of both ASNs and IPV4 digits, so I guess it's not =
that novel.
>=20
> As I'm not the author of the document - only the initiator of the =
translation - I'm not sure if I'm the right person to answer this =
question :) However, I do think it is an interesting discussion on how =
far "the world has already settled on" different IPv6 implementation =
techniques. There are relatively only a few mature operational IPv6 =
implementations at the moment and the intention of this document is to =
have people think of a structure for their address plan and give them =
some pointers.=20
>=20
I believe based on my observation and experience that it describes a =
relatively common practice, but, not
one which has in any way been standardized. It is one approach that is =
available and which has proven
useful to others. Both the BCD and Hex translation techniques are in =
relatively common use, but, the BCD
mechanism seems to be somewhat more common.
The important thing to be careful about with BCD is that you do not =
attempt to represent all four octets of
an address with each cluster representing an octet because you will =
violate the "first 12 bits of a static
suffix must be zero" rule (following that rule avoids accidental =
conflicts with stateless autoconf).
Owen
