Subject: off-link model in the 6lowpan talk: draft-ietf-6lowpan-nd-07

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Mon, 9 Nov 2009 19:16:10 -0600

Humble apologies for not reading this lowpan doc, but I have listened to
its core ideas during the past IETFs prezos and understand the link
model being used for it.   I still have some general comments that are
worth discussing when bringing such work to 6man.

Note that if the multi-link, multi-hop network has all client nodes as
off-link to each other, then there is only one type of regular ND
(RFC4861) RA that can signal off-link.  This is an RA with no PIO
(Prefix Information Option).   So if the RA has no PIO, how are the
lowpann client nodes acquiring their IPv6 address global address without
SLAAC getting no prefix from?  In 6man, we would like to know how are
the lowpan clients acquiring their address and do they even have a
global v6 address?  I think I heard some mention of ULA, so that gives
me a hint of global address use because ULA has same scope as a Globally
Unique Address (GUA).   Therefore it would be interesting to see the
IPv6 ND RA config on the lowpan edge routers.

Anyone has working models of this work to demo to us during any future
IETF?

Thanks,

Hemant

---

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Mon, 9 Nov 2009 20:05:58 -0600

>-----Original Message-----
>From: Carsten Bormann [mailto:[email-masked]] 
>Sent: Tuesday, November 10, 2009 10:34 AM
>To: Hemant Singh (shemant)
>Cc: [email-masked]; 6lowpan; Pascal Thubert (pthubert); Jonathan Hui;
Samita Chakrabarti; Erik Nordmark; Dave Thaler
>Subject: Re: off-link model in the 6lowpan talk:
draft-ietf-6lowpan-nd-07

>Hemant,

>it is probably best if you copy [email-masked] for discussing this.

Will do - thanks.

>> Note that if the multi-link, multi-hop network has all client nodes  
>> as off-link to each other, then there is only one type of regular ND

>> (Prefix Information Option).

>Our RAs typically have a PIO with L bit off and A bit on (actually  
>usually a 6IO with a couple bits of additional information, but since  
>-07 the classic PIO works too).

That is my very point.  ND as specified by RFC 4861 has no means to
signal a prefix as off-link, so the L bit cleared is not signaling
off-link. 

>> Therefore it would be interesting to see the IPv6 ND RA config on  
>> the lowpan edge routers.
>>
>> Anyone has working models of this work to demo to us during any  
>> future IETF?

>I'm sure that can be arranged in Anaheim.

Great.  

Thanks,

Hemant

---

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Tue, 10 Nov 2009 03:54:16 +0100

Hi Zach:

A useful (informational) reference. 

I understood that we now call the whole LoWPAN the link though we still 
restrict the use of link local for the radio range.

Autoconf still uses the radio range as link. Also it is has:

"
   o  There is no mechanism to ensure that IPv6 link-local addresses are
      unique across multiple links, hence they can not be used to
      reliably identify routers.
"

Which we make untrue: 6LowPAN ND introduces that mechanism.

We took great care to validate uniqueness of the link local address
across 
a bounded set (that is not limited to the link local scope) that we used

to call the subnet and now call the non transitive link.

Thus we still can use the link local address of our first hop routers. 

We tend to agree with the conclusions like use the global addresses for 
most everything but the reasons are slightly different.

I'm unsure what pages you want to save with this. But I trust you'll do
good as usual.

Pascal

>From: [email-masked] [mailto:[email-masked]] On
Behalf Of Zach Shelby
>Sent: mardi 10 novembre 2009 02:43
>To: Carsten Bormann
>Cc: Hemant Singh (shemant); [email-masked]; 6lowpan; Dave Thaler
>Subject: Re: [6lowpan] off-link model in the 6lowpan
talk:draft-ietf-6lowpan-nd-07
>
>Carsten presented 6lowpan-nd to 6man today, which was useful. A
>comment that came in from Dave Thaler was to re-use the autoconf
>model. Everyone should take a look at:
>
>http://tools.ietf.org/html/draft-ietf-autoconf-adhoc-addr-model-00
>
>This greatly simplifies the editorial/terminology work for us in
>6lowpan. It looks like we can directly reference this autoconf
>addressing model. It should remove about 3-4 pages from our draft ;-)
>They have come to the same conclusions regarding the off-link model,
>use of IPv6 addresses and DAD. Otherwise it looks like 6lowpan-nd is
>technically compatible with that model.
>
>Zach
>
>On Nov 10, 2009, at 10:34 , Carsten Bormann wrote:
>
>> Hemant,
>>
>>> as off-link to each other, then there is only one type of regular
>>> ND (RFC4861) RA that can signal off-link.  This is an RA with no
>>> PIO (Prefix Information Option).
>>
>> usually a 6IO with a couple bits of additional information, but
>> since -07 the classic PIO works too).
>>
>>> So if the RA has no PIO, how are the lowpann client nodes acquiring
>>> their IPv6 address global address without SLAAC getting no prefix
>>> from?  In 6man, we would like to know how are the lowpan clients
>>> acquiring their address and do they even have a global v6 address?
>>
>> Yes, they do have global addresses; that is the whole point of
>> running IPv6.
>>
>>> I think I heard some mention of ULA, so that gives me a hint of
>>> global address use because ULA has same scope as a Globally Unique
>>> Address (GUA).
>>
>> The slide about ULA was for the disconnected case ("ad-hoc LoWPAN").
>>
>> (Does anyone have an implementation with them here in Hiroshima?)
>>
>> Gruesse, Carsten
>>
>>
>> _______________________________________________
>> 6lowpan mailing list
>> [email-masked]
>> https://www.ietf.org/mailman/listinfo/6lowpan
>
>--
>http://www.sensinode.com
>http://zachshelby.org - My blog "On the Internet of Things"
>Mobile: +358 40 7796297
>
>Zach Shelby
>Head of Research
>Sensinode Ltd.
>Kidekuja 2
>88610 Vuokatti, FINLAND
>
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---

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Mon, 9 Nov 2009 21:37:25 -0600

Carston,

Yes, that is the closure.  Not on-link means send traffic to the default
router(s).  We just do not want language in any document to proliferate
that ND has a means to specify a prefix as off-link.  

Hemant

-----Original Message-----
From: Carsten Bormann [mailto:[email-masked]] 
Sent: Tuesday, November 10, 2009 11:12 AM
To: Hemant Singh (shemant)
Cc: [email-masked]; [email-masked]; Pascal Thubert (pthubert); Jonathan
Hui; Samita Chakrabarti; Erik Nordmark; Dave Thaler
Subject: Re: off-link model in the 6lowpan talk:
draft-ietf-6lowpan-nd-07

On Nov 10, 2009, at 11:05, Hemant Singh (shemant) wrote:

> ND as specified by RFC 4861 has no means to

Right, L=0 does not say "this is off-link", it says "I'm not saying it  
is on-link".
(RFC 4861, section 4.6.2 and 6.3.4.)
Now, if nobody ever says it is on-link, it remains off-link.

Gruesse, Carsten

---

From: Carsten Bormann <[email-masked]>
Date: Tue, 10 Nov 2009 10:34:05 +0900

Hemant,

> acquiring their address and do they even have a global v6 address?

Yes, they do have global addresses; that is the whole point of running  
IPv6.

Gruesse, Carsten

---

From: Zach Shelby <[email-masked]>
Date: Tue, 10 Nov 2009 10:42:33 +0900

Zach

-- 
http://www.sensinode.com
http://zachshelby.org - My blog “On the Internet of Things”
Mobile: +358 40 7796297

Zach Shelby
Head of Research
Sensinode Ltd.
Kidekuja 2
88610 Vuokatti, FINLAND

---

From: Carsten Bormann <[email-masked]>
Date: Tue, 10 Nov 2009 11:12:03 +0900

Gruesse, Carsten

---

From: Suresh Krishnan <[email-masked]>
Date: Tue, 10 Nov 2009 21:25:39 -0500

Hi Hemant,

> (Prefix Information Option).   

This is not accurate. This can also be signaled using an RA including a 
PIO by setting L=0 in the PIO.

> So if the RA has no PIO, how are the 

The A bit can still be set in the PIO to allow for SLAAC.

Thanks
Suresh

---

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Tue, 10 Nov 2009 20:30:29 -0600

Suresh, 

I have already given an explanation.  There is no means in IPv6 ND to
signal a prefix as off-link! It's just that when the L-bit is cleared
the host has to send traffic to the default router.

Hemant

-----Original Message-----
From: Suresh Krishnan [mailto:[email-masked]] 
Sent: Wednesday, November 11, 2009 11:26 AM
To: Hemant Singh (shemant)
Cc: [email-masked]; Pascal Thubert (pthubert); [email-masked];
[email-masked]; [email-masked]; Erik Nordmark; Dave Thaler
Subject: Re: off-link model in the 6lowpan talk:
draft-ietf-6lowpan-nd-07

Hi Hemant,

---

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Tue, 10 Nov 2009 20:33:15 -0600

Snipped from RFC 4861 is this text:

[Note, however, that a Prefix Information option with the on-link flag
set to zero conveys no information concerning on-link determination and
MUST NOT be interpreted to mean that addresses covered by the prefix are
off-link.]

Hemant

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Hemant Singh (shemant)
Sent: Wednesday, November 11, 2009 11:30 AM
To: Suresh Krishnan
Cc: Pascal Thubert (pthubert); [email-masked]; Erik Nordmark; Dave
Thaler; [email-masked]; [email-masked]
Subject: RE: off-link model in the 6lowpan talk:
draft-ietf-6lowpan-nd-07

Suresh, 

Hemant

-----Original Message-----
From: Suresh Krishnan [mailto:[email-masked]] 
Sent: Wednesday, November 11, 2009 11:26 AM
To: Hemant Singh (shemant)
Cc: [email-masked]; Pascal Thubert (pthubert); [email-masked];

Hi Hemant,

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