Creating an IPv6 addressing plan for end users

Owen DeLong owen at delong.com
Thu Mar 24 08:45:15 CDT 2011


On Mar 24, 2011, at 1:06 AM, Nathalie Trenaman wrote:

> Hi Liudvikas,
> 
> Thank you very much for your feedback. 
> 
> On Mar 23, 2011, at 4:56 PM, Liudvikas Bukys wrote:
> 
>> Hi, I saw your document "Preparing an IPv6 Addressing Plan" after its URL was posted to NANOG.
>> 
>> I have one small comment that perhaps you would consider in future revisions:
>> 
>> 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.
>> 
>> 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.
> 
> 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. 
> 
>> 
>> Without an explicit discussion, this point may be missed by some readers -- especially since this is a training document.
>> 
>> Just my opinion!
>> 
>> 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.
> 
> 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. 
> 
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





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