Re: encoding link ID in link-local addrs (Re: about violation of standards) - problem statement

[Alexandre Petrescu <[e-mail]>]

Le 24/04/2019 à 17:04, Ole Troan a écrit :
> 
> 
>> On 24 Apr 2019, at 16:53, Alexandre Petrescu 
>> <[e-mail]> wrote:
>> 
>> I will add in the draft that Cisco also supports fe80:1::1.  I 
>> think I forgot that, but now that you say it I trust it too.
>> 
>>> I don’t see any justification to allowing the 54 bits in the 
>>> network 64 bit portion of the link local address to be changed 
>>> from all 0s.
>> 
>> I dont understand you.
>> 
>> You say fe80:1::1 works on Cisco, but then you say you seee no 
>> justification to allow the 54bits to change from 0.  The first 1
>> in fe80:1::1 means a change from 0.
>> 
>> So, do you mean Cisco is wrong?
>> 
>> Or do you mean such things are wrong and the RFC is right?
> 
> That an implementation allows you to do something does not mean that 
> it is supported (in the product sense) nor that the RFC is wrong. 
> (And I am very familiar with why that particular implementation does 
> what it does).
> 
> This has been repeated many times over the last few years. If you 
> want this changed, please provide a problem statement.

Ole,

These are three tries for a problem statement:

1 A rejected Errata to RFC4291 "IPv6 Addr Archi" on the topic of link-
   local addresses 'would need' a draft.  (The errata ID is 4406; the URL
   is https://www.rfc-editor.org/errata/eid4406)

Do you disagree with the recommendation of this Errata?

2 IPv6 link-local addresses are typically self-configured according to 4
   RFCs and relying on the fe80::/10 IANA allocation, RFC 54 0 bits, and
   RFC MAC-based 64bit Interface IDs.  In some cases, it is advantageous
   to manually configure link-local addresses.  This is useful for easy
   remembering by humans, and for parameter resilience during
   network interface replacement.

   Manual configuration of an LL may use short IID and Subnet ID
   The Subnet ID presence in the link-local address is useful in some
   wireless settings where the subnet structure parameters depend on the
   link locality.  Other settings may also benefit.

   When manually setting the link-local address it is necessary to know
   the length of the prefix of the subnet on which this link-local
   address is present.  This length is necessary for on-link
   determination.

   Implementation status: manually configuring link-local addresses is an
   operation permitted by some Operating Systems but forbidden by others.
   The ones that permit it need a parameter for the length of the prefix.
   The length of the prefix is sometimes 10 (cf. IANA allocation), at
   times 64 (cf. RFC assignment), at times 128 (cf. 2 RFCs) and other
   intermediary values are known to work.

Is this 2nd try along your line of thought?

3 more problem statements about 'some wireless settings' can be found in
   the IPWAVE WG Problem Statement draft.

Is this 3rd kind of problem statement something that may be answering 
your request to provide a problem statement?

Alex

> 
> Ole
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