Subject: [Autoconf] Discussion on link types and status of documents

From: "Teco Boot" <[email-masked]>
Date: Fri, 14 Mar 2008 16:12:11 +0100

Hi,

I reread RFC2501 and I think this document is still valid. It describes
characteristics of MANETs and MANET links in detail. Both Autoconf documents
refer to it. Maybe refer more explicitly to it?

When looking at RFC4861, I think a MANET link may have all described link
type properties. MANET links may be P2P or multi access, broadcast or
non-broadcast, shared or non-shared, can have fixed or variable MTU and may
have or may not have asymmetric reachability. In short, nothing is planned
(ad hoc) and nothing is stable (mobile).

There was posted comment on using term MANET Interface for text that was
about links. This is still not corrected in the active MANET-Arch document.
I think we should try to line up MANET-Arch and PS with RFC4861 as soon as
possible, with ref to RFC2501 when applicable.

On lining up the documents: parts of the architecture is in the PS document.
I see no reason that section 3. MANET Categories is not part of MANET-Arch. 
Same comment on section 2. Terminology; information is split in the two
documents. I see no reason for this split.

A while ago, we discussed an scenario with ad hoc classical, symmetric
reachability links only. This could be an important, e.g. supporting plug
and play consumer and business gadgets with for example mix of Bluetooth,
USB/WUSB, WiFi, WiMAX and 3G technology. MIP6 and NEMO are related to this
scenario, but this will only work when HA is reachable, e.g. Subordinate
MANET. I am not sure MEXT addresses all requirements, especially when a
MANET routing protocol is introduced for supporting disconnected operation
and RO within the topology (Nested NEMO RO). The question is, shall we work
on this scenario? If yes, it must be included in our documents.
 
Teco.

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From: "Ian Chakeres" <[email-masked]>
Date: Mon, 17 Mar 2008 17:27:45 +0530

I'd like to chime in on this conversation by saying that "MANET link"
is not a good term. MANET's (and the MANET WG protocols) run over lots
of kinds of different physical and logical links. It just so happens
that they may also often run over links with asymmetric reachability.

If a new "link type" needs to be defined, it should not contain the
term MANET. I see link type as an independent concept.

Ian Chakeres

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From: Jari Arkko <[email-masked]>
Date: Mon, 17 Mar 2008 15:11:55 +0200

Right.

Jari

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From: Alexandru Petrescu <[email-masked]>
Date: Tue, 18 Mar 2008 16:27:15 +0100

Ian Chakeres wrote:
>  is not a good term. MANET's (and the MANET WG protocols) run over
> lots of kinds of different physical and logical links. It just so
> happens that they may also often run over links with asymmetric
> reachability.

Maybe then trying to describe link-types in the AUTOCONF Architecture is
actually listing those kinds of different physical and logical links on
which MANET have been run?

I have not run MANET.  But I ran other IPv6 protocols, and AUTOCONF is
not limited to MANET, and the list of link-types I used are the following:

Ethernet
Bluetooth
PPP
RS232C
USB

Alex

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> mailing list [email-masked] 

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From: Shubhranshu <[email-masked]>
Date: Wed, 19 Mar 2008 09:18:29 +0530

> not limited to MANET, and the list of link-types I used are the following:

I agree that defining term "MANET link" is not appropriate but I do
not see any point in listing all the links on which MANET has been
run. MANET has not been run on any particular L2 technology does not
imply that MANET cannot run on that technology.

I agree that having "IP Link Model" for MANET explained clearly would
help here. The challenge is to express precisely, with appropriate
terminologies what the MANET community has been assuming while
designing and running MANET protocols. The current MANET Architecture
document have text on this but since these questions keep coming, I am
inclined to think that including more specific text would help.

- Shubhranshu

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From: Alexandru Petrescu <[email-masked]>
Date: Wed, 19 Mar 2008 11:17:15 +0100

Shubhranshu wrote:
>>> I'd like to chime in on this conversation by saying that "MANET
>>> link" is not a good term. MANET's (and the MANET WG protocols)
>>> run over lots of kinds of different physical and logical links.
>>> It just so happens that they may also often run over links with
>>> asymmetric reachability.
>> Maybe then trying to describe link-types in the AUTOCONF
>> Architecture is actually listing those kinds of different physical
>> and logical links on which MANET have been run?
>> 
>> I have not run MANET.  But I ran other IPv6 protocols, and AUTOCONF
>> is not limited to MANET, and the list of link-types I used are the
>> following:
>> 
>> Ethernet Bluetooth PPP RS232C USB
> 
> run.

How would one otherwise start describing link types?

> MANET has not been run on any particular L2 technology does not imply
> that MANET cannot run on that technology.
> 
>  document have text on this but since these questions keep coming, I
> am inclined to think that including more specific text would help.

Well, the current draft does not describe 'link type', neither 'IP Link
Model', can't find.  What do you mean by current MANET Architecture
document having text on this?  Which part, thank you.

If one understands link types the way people having deployed ND and DHCP
understood link types then one wouldn't see a problem in running ND and
DHCP on the link types on which MANET runs.

Alex

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From: "Charles E. Perkins" <[email-masked]>
Date: Wed, 19 Mar 2008 04:26:10 -0700

Hello Alex,

> How would one otherwise start describing link types?

I think of them as links over which IP can be run.  There is no prior 
restriction
that they must run only protocols defined in [manet] wg, or [dhc] wg for 
that matter.
There is no prior restriction that the addresses used by IP over these 
links must
be able to be aggregated into contiguous address ranges.

> DHCP on the link types on which MANET runs.

One can certainly run IP over a link without being required to also
run DHCP and/or ND.  IP was around for a long time before those
two protocols.

Moreover, I am sure that we can have useful networks running various
manet protocols that do not run DHCP or ND.  Of course, as Joe Macker
pointed out quite forcefully at the autoconf meeting, we can certainly
have manets that DO run DHCP (and, presumably, ND).

I'd be very, very surprised and unhappy if someone were able to
legislate that manets were REQUIRED to run DHCP or ND.

My own opinion is that there are many instances in which it is not
at all appropriate to run DHCP (as currently specified), and that
these instances are more common percentagewise, perhaps even
predominant, in mobile ad-hoc networks.  Which in no way implies
that one should not consider DHCP when appropriate!

Maybe instead of arguing over link types, it would be better to
have a task force making a report about when DHCP is appropriate,
and let the working group get on with other useful work.

Regards,
Charlie P.

---

From: Alexandru Petrescu <[email-masked]>
Date: Wed, 19 Mar 2008 14:28:07 +0100

Charles E. Perkins wrote:
>>> I agree that defining term "MANET link" is not appropriate but I 
>>> do not see any point in listing all the links on which MANET has 
>>> been run.
>>> 
>> 
>  restriction that they must run only protocols defined in [manet] wg,
>  or [dhc] wg for that matter. There is no prior restriction that the 
> addresses used by IP over these links must be able to be aggregated 
> into contiguous address ranges.
> 
> 
>> If one understands link types the way people having deployed ND and
>>  DHCP understood link types then one wouldn't see a problem in 
>> running ND and DHCP on the link types on which MANET runs.
>> 
> 
> run DHCP and/or ND.  IP was around for a long time before those two 
> protocols.
> 
>  manet protocols that do not run DHCP or ND.  Of course, as Joe
> Macker pointed out quite forcefully at the autoconf meeting, we can 
> certainly have manets that DO run DHCP (and, presumably, ND).
> 

Right, not trying to mandate DHCP/ND.  It's just that they're always
there on in many unix systems and one may have a hard time turning them off.

> My own opinion is that there are many instances in which it is not at
>  all appropriate to run DHCP (as currently specified), and that these
>  instances are more common percentagewise, perhaps even predominant, 
> in mobile ad-hoc networks.  Which in no way implies that one should 
> not consider DHCP when appropriate!
> 
> Maybe instead of arguing over link types, it would be better to have 
> a task force making a report about when DHCP is appropriate, and let 
> the working group get on with other useful work.

I'm trying to identify the overall goals and scope in AUTOCONF.  Not
sure about a separate task force at this time.  I'm having the feeling
that much discussion is already happening behind the AUTOCONF scenes and
very little at the forefront, in my perception.

HEre and now, the size of room for progress is proportional to the gap
between what's stated at the meeting/mailing list and what's stated in
the documents.

This is in my humble opinion.

Alex

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From: Emmanuel Baccelli <[email-masked]>
Date: Wed, 19 Mar 2008 14:50:06 +0100

Hello Charlie,

> and let the working group get on with other useful work.

I guess the problem statement draft is supposed to identify if/when DHCP 
is appropriate or not. Section 5.1 of the document describes DHCP 
limitations in MANETs, so by contraposition, it also talks about cases 
when DHCP is appropriate in MANETs ;)

Maybe modifications to Section 5 would be a a good starting point to 
address the subject?

Emmanuel

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From: "Teco Boot" <[email-masked]>
Date: Wed, 19 Mar 2008 14:52:30 +0100

Hi Charlie,

I have some thoughts on running IPv6 without ND for link layer address
discovery.

> legislate that manets were REQUIRED to run DHCP or ND.

Can we run IPv4 over Ethernet without ARP?
Can we run IPv6 over Ethernet without ND?
Should Autoconf work on a protocol for link layer address discovery for
MANET links (link between MANET interfaces)?
Or snoop L2 header info from for example received NHDP packets?

I am with you when you say: let's try to reduce overhead.

Regards, Teco

---

From: Shubhranshu <[email-masked]>
Date: Thu, 20 Mar 2008 09:02:48 +0530

Hello Charlie, Emmanuel,

Please see inline comments

> when DHCP is appropriate in MANETs ;)

Section 3 does a good separation between autonomous and subordinate
MANET. In the autonomous MANET, no DHCP server would be available and
thus node needs to rely on some other approach to configure
addresses/prefixes. On the other hand in the subordinate MANET,
availability of DHCP server can be assumed and thus a MANET node could
contact it (directly or via relay agent) for configuration of
addresses/prefixes.

- Shubhranshu

---

From: Shubhranshu <[email-masked]>
Date: Thu, 20 Mar 2008 09:05:05 +0530

Alex,

> How would one otherwise start describing link types?

I assumed in my previous mail that by link you meant different L2
technologies since you listed bluetooth, USB, Ethernet, etc. One could
do that by describing its properties, behavior as seen by the IP.

> document having text on this?  Which part, thank you.

I meant section 5.

- Shubhranshu

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 20 Mar 2008 11:38:11 +0100

> do that by describing its properties, behavior as seen by the IP.

YEs, that is what I mean by 'link': a certain L2 technology.  I agree 
one would describe its properties and behavior as  seen by IP.

>> document having text on this?  Which part, thank you.

But section 5 "Addressing & the MANET Prefix Model" does not describe 
link types.

Alex

---

From: "Charles E. Perkins" <[email-masked]>
Date: Thu, 20 Mar 2008 15:29:00 -0700

Hello Shubhranshu,

Shubhranshu wrote:
>  ...   in the subordinate MANET,

Do you really think so?  Is every network attached to the
Internet managed by DHCP?  Shouldn't we allow for
networks that follow the stateless autoconfiguration
model of IPv6?

Perhaps we should instead say that, in many
circumstances, DHCP is appropriate for use
with subordinate networks.

Regards,
Charlie P.

---

From: Shubhranshu <[email-masked]>
Date: Fri, 21 Mar 2008 08:01:08 +0530

Hello Charlie,

> with subordinate networks.

In my previous mail, I didn't mean always (else I'd have used
"should"). So we are on the same page. And thats why we have IPv6
stateless autoconfiguration as well.

Regards,
Shubhranshu

---

From: "Charles E. Perkins" <[email-masked]>
Date: Wed, 19 Mar 2008 07:22:59 -0700

Hello Teco,

> Can we run IPv4 over Ethernet without ARP?

Of course it would be possible.  But, resolving IP
addresses on a nice broadcast medium like Ethernet
is so conveniently done by ARP, it would seem silly
to do it some other way.  Plus, for most hosts on
an IPv4 Ethernet there is typically not any question
about the next hop.

> Can we run IPv6 over Ethernet without ND?

I'd answer pretty much the same way for this.

> MANET links (link between MANET interfaces)?

The fact that typical MANET media don't offer
the nice broadcast physics of Ethernet motivates
me to answer this in the negative.

> Or snoop L2 header info from for example received NHDP packets?

Well, that seems fine to me, but I'm sure neither
one of us would suggest that as a replacement for
Ethernet broadcast.

> I am with you when you say: let's try to reduce overhead.

Thanks!  I think the meeting of the [roll] working
group made the importance of this even more clear.

Regards,
Charlie P.

---

From: "Charles E. Perkins" <[email-masked]>
Date: Mon, 24 Mar 2008 05:43:10 -0700

Hello Shubhranshu,

Yes, I think we are in agreement on this.
But this model of operation was not very clear
from the way the discussion transpired at the
recent IETF meeting.  As long as the DHCP-style
of stateful autoconfiguration is enabled and
yet not in any way mandated, I think most people
would be happy.

Regards,
Charlie P.