Subject: RE: is that inconsistent in RFC4291?

From: "Gray, Eric" <[email-masked]>
Date: Wed, 26 Apr 2006 14:36:34 -0400

Brian,

	This could be taken two ways: either (portions of) the RFC must be 
assumed to be meaningless except in the context of prior discussions on 
the E-Mail list (hence, only somebody who has read the entirety of the 
IPv6 mailing list is qualified to read and ask questions about this RFC), 
or those same parts of the RFC do not provide sufficient clarification 
of intent.

	Surely you're not saying everybody should familiarize themselves 
with all of the discussions from the mailing list in order to understand 
the RFC.

	The prior discussion does not actually address the question - except

that it might have provided enough clue to make someone stop asking at the 
time.

	In both discussions, disparity between definition and format means 
that a very large number of addresses are somehow reserved (apparently for 
future use).  Any address that starts with '1111111010b' is a link-local 
address (with the last 64 bits are used to provide an interface identifier) 
according to the definition - except that all values in the fe80::/10 range 
that do not start with 

  '1111111010000000000000000000000000000000000000000000000000000000b'

are (currently?) invalid.

	IMO, while the meaning may be fairly clear given the discussions
that have occurred, the fact that this was discussed before and is being 
discussed again is a pretty good indication that it will be discussed at 
least one more time unless it is documented somewhere other than in E-Mail.

	Is it possible to provide clarification in the form of an errata?

--
Eric

--> -----Original Message-----
--> From: Brian Haberman [mailto:[email-masked]] 
--> Sent: Wednesday, April 26, 2006 11:02 AM
--> To: Lawrence Zou
--> Cc: [email-masked]
--> Subject: Re: is that inconsistent in RFC4291?
-->
--> Here is a link to the mailing list archive where this discussion 
--> has occurred before:
--> http://www1.ietf.org/mail-archive/web/ipv6/current/msg05628.html
--> 
--> Regards,
--> Brian
--> 
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---

From: Soohong Daniel Park <[email-masked]>
Date: Thu, 27 Apr 2006 17:19:14 +0900

While adopting ULA into the local networks, I am curious
how to set universal/local bit of Interface ID. There is
no any mention in RFC4193. Which is correct ? 1 or 0 ?

Thanks in advance.

Daniel (Soohong Daniel Park)
Mobile Convergence Laboratory, SAMSUNG Electronics.

---

From: Roger Jorgensen <[email-masked]>
Date: Thu, 27 Apr 2006 10:28:13 +0200 (CEST)

> no any mention in RFC4193. Which is correct ? 1 or 0 ?

1 is for those assigned to you while 0 are free for any to use last I read 
up on the subject.

-- 

------------------------------
Roger Jorgensen              |
[email-masked]           | - IPv6 is The Key!
-------------------------------------------------------

---

From: Eliot Lear <[email-masked]>
Date: Thu, 27 Apr 2006 12:48:48 +0200

Roger,
> 1 is for those assigned to you while 0 are free for any to use last I read 

By my reading I think you have it backwards.  Here is the relevant text:

      L                 Set to 1 if the prefix is locally assigned.
                        Set to 0 may be defined in the future.  See
                        Section 3.2 for additional information.

Today, so far as I know, there is no defined allocation plan or system
for one to set that bit to 0.

Eliot

---

From: Roger Jorgensen <[email-masked]>
Date: Thu, 27 Apr 2006 13:03:18 +0200 (CEST)

>                         Section 3.2 for additional information.

sorry my mistake.

> for one to set that bit to 0.

Some months ago I asked about ULA and there was some discussion, one of 
them should include a link to a discussion about some ideas of a plan. 
Maybe they've moved on? Haven't seen anything more about it.

(the list was either [email-masked] or this list, don't remember and my 
mailarchive is a bit offline right now :( )

--

---

From: Brian Haberman <[email-masked]>
Date: Thu, 27 Apr 2006 10:58:47 -0400

> for one to set that bit to 0.

I don't believe the original poster was asking about the L bit in the 
ULA
prefix, rather about the U/L but in the Interface Identifier.  The U/L 
bit in
the IID should not be impacted by the use of ULAs.  Rather, its settings
are based on the rules in Section 2.5.1 of RFC 3513.

Regards,
Brian

---

From: Bob Hinden <[email-masked]>
Date: Thu, 27 Apr 2006 09:15:44 -0700

Daniel,

> no any mention in RFC4193. Which is correct ? 1 or 0 ?

First to clarify your question, I think you are asking about the  
universal/local bit discussed in the forth paragraph of Section  
2.5.1. "Interface Identifiers" of RFC4291.  Not the "L" bit in RFC4193.

The ULA document defines how to creates a local prefix for the site.   
A node would create it's interface IDs in the normal matter as  
specified in RFC4291.  Nothing special is required or even desired.   
The L bit setting is independent of the prefix (global unicast, link- 
local, ULA, etc.).

Bob

p.s. I think some of the other responses to your email misinterpreted  
your question.  Or else, I did :-)

---

From: Soohong Daniel Park <[email-masked]>
Date: Fri, 28 Apr 2006 09:09:33 +0900

Bob, 

> 2.5.1. "Interface Identifiers" of RFC4291.  Not the "L" bit in RFC4193.

Yes. Definitely L=1

> The L bit setting is independent of the prefix (global unicast, link- 

So, universal/local bit = 1. Because ULA provides its globally uniqueness.
Correct ?

Thanks,

---

From: Bob Hinden <[email-masked]>
Date: Fri, 28 Apr 2006 07:23:56 -0700

Daniel,

> So, universal/local bit = 1. Because ULA provides its globally  

No, the universal/local bit could be 1 or 0, depending on the source  
of the token used to create it.

 From the RFC4291 IPv6 Address Architecture:

    2.5.1.  Interface Identifiers

    Interface identifiers in IPv6 unicast addresses are used to identify
    interfaces on a link.  They are required to be unique within a  
subnet
    prefix.  It is recommended that the same interface identifier not be
    assigned to different nodes on a link.  They may also be unique over
    a broader scope.  In some cases, an interface's identifier will be
    derived directly from that interface's link-layer address.  The same
    interface identifier may be used on multiple interfaces on a single
    node, as long as they are attached to different subnets.

    Note that the uniqueness of interface identifiers is independent of
    the uniqueness of IPv6 addresses.  For example, a Global Unicast
    address may be created with a local scope interface identifier and a
    Link-Local address may be created with a universal scope interface
    identifier.

Hope that helps.

Bob