Subject: [Int-area] AUTOCONF charter

From: Thomas Narten <[email-masked]>
Date: Fri, 07 Oct 2005 09:09:20 -0400

--------
Note: I'm moving discussion of an offline thread to int-area and
manetautoconf to broaden the discussion.

Background: myself and others have expressed concerns about the
autoconf charter. IMO, the current charter has some significant issues
and the focus of the work needs to be redirected if this effort is
going to have a good outcome.

I'll post some background messages and then reply to an ongoing
thread.

Here is an excerpt from an earlier message:

From: Thomas Narten <[email-masked]>
To: Margaret Wasserman <[email-masked]>
cc: [email-masked], Ralph Droms <[email-masked]>,
    Bob Hinden <[email-masked]>,
    Bernard Aboba <[email-masked]>, Alex Zinin <[email-masked]>,
    Mark Townsley <[email-masked]>,
    Brian E Carpenter <[email-masked]>, [email-masked],
    [email-masked]
Date: Tue, 27 Sep 2005 11:51:16 -0400
Subject: Re: AUTOCONF Chartering Call 

Hi. I just looked at what I assume is the most recent charter
(margaret sent it out on sept 22).

Second, looking at the charter, I think the first three paragraphs
completely miss the most important aspect of this work...

>Ad-Hoc Network Autoconfiguration (autoconf) Working Group
>
>Chairs:
>Shubhranshu Singh <[email-masked]>
>Thomas Clausen <[email-masked]>
>
>Internet Area Directors:
>Mark Townsley <[email-masked]>
>Margaret Wasserman <[email-masked]>
>
>Internet Area Advisor:
>Margaret Wasserman <[email-masked]>
>
>Mailing List:
>
>General Discussion: [email-masked]
>To Subscribe: [email-masked]
>
>In order to communicate among themselves, ad hoc nodes (refer to RFC
>2501) need to configure their network interface(s) with local
>addresses that are valid within an ad hoc network.

yes. But this is not enough to communicate. There also needs to be a
model/framework/architecture that defines an "ad hoc subnet":

  - what is the subnet model? I.e., for a collection of links, what
    are the boundaries of a "subnet", where each node is part of the
    same ad hoc network?

  - how are packets forwarded within a subnet? How is address
    resolution done? How does a sender decide whether a destination on
    the "subnet" is directly reachable, or is reachable through  a
    forwarding node?

  - How is multicast traffic distributed within the subnet?

  - in IPv6, how are RAs distributed?

>Ad hoc nodes may also need to configure globally routable addresses,
>in order to communicate with devices on the Internet.

Depending on the answers to the questions  above, this may not be an
issue at all. I.e., global addresses could be distributed via RAs. Why
(or why not) is this insufficient?

>From the IP layer perspective, ad hoc networks present severa
>challenges. Unlike in the traditional IP networks, each ad hoc node,
>besides being a traffic end-point,
>should be capable of forwarding traffic destined for other hosts.

This would seem to be making assumptions about what the subnet model
is. I.e., how one delivers packets to other destinations on the same
"ad hoc" subnet. How is that done? Is that what this WG needs to
decide, or has this already been decided? If the latter, where is that
documented?

>Additionally, nodes constituting an ad-hoc network do not share access
>to a single multicast-capable link for signaling.

so a key architectural question is whether an "ad hoc subnet" will
emulate multicast service. And if not, what the implications are and
whether that is actually a desirable direction to go in.

Has this issue already been decided? Is this WG supposed to figure
this out and come up with an approach/solution?

>Many protocol
>specifications used in the traditional IP networks e.g. RFCs 2462,
>2463 etc. do, however, assume that subnet-local signals (e.g.
>link-local multicast signal) are received by each of the hosts on the
>particular subnet without being forwarded by the routers defining the
>subnet boundary. Hence ad hoc networks, (as defined and understood by
>the IETF MANET WG) supporting routing protocol at the network layer in
>order to provide multi-hop communication, cannot use these protocol
>specifications as-is.

A reason  my previous question is so critical is whether we are better
off emulating multicast (so all multicast applications work as is), or
whether every higher-layer protocol that uses multicast has to be
rewritten to work over  an "ad hoc subnet"? I sure hope we aren't
doing the latter...

>The main purpose of the AUTOCONF WG is to standardize mechanisms to be
>used by ad hoc nodes for configuring unique local and/or globally
>routable IPv6 addresses.

IMO, this above is the tip of the iceberg, and it is the larger
questions that must be dealt with. The addressing part is just one
component of the bigger picture, and without a coherent bigger
picture, none of this makes sense.

>The ad hoc nodes under consideration are,
>once configured, expected to be able to support multi-hop
>communication by running the MANET routing protocol developed by the
>IETF MANET WG.

Which document is this? Is there just one?

And, is this a routing protocol that carries unicast, or is this the
definition of the abstract service an "ad hoc subnet" provides?
 
Thomas

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---

From: Ralph Droms <[email-masked]>
Date: Fri, 07 Oct 2005 09:44:51 -0400

>   - in IPv6, how are RAs distributed?

I think Thomas has asked several fundamental questions that need to be
answered before work on address assignment can make progress.

It seems to me we need to know exactly how and at what layer the
specific hardware and operational characteristics of a MANET are
accommodated, and which layers of the protocol stack are expected to
work unchanged.

- Ralph

---

From: "Charles E. Perkins" <[email-masked]>
Date: Fri, 07 Oct 2005 18:52:51 +0300

Hello Thomas,

I have some possible answers to your questions.

But first, a little background.  In our group, we implemented a
number of ad hoc networks, and wanted the nodes to be able to
have addresses.  So we devised a way for them to get addresses.
It worked.  Other people noticed the same problem, and designed
other ways that worked.  We got together, had a couple of BOFs,
and put together a charter that seemed to make sense to the
practitioners who wanted to agree on a standard method for
getting addresses.  So that's where I'm coming from.

>model/framework/architecture that defines an "ad hoc subnet":
Not necessarily, at least not in any formalized rigid way.  People who are
building these things like crazy don't seem to have any terrible problems
getting the devices to communicate.

>    are the boundaries of a "subnet", where each node is part of the
Often, there is no subnet model.  If there is one, then it's a matter of 
debate
how to best impose it.  For the purposes of my initial interest, you could
consider the whole ad hoc network as having no hierarchical addressing.
You could also say that the extent of the subnet is the same as the extent
of the ad hoc network, but this is only one possible model.

>  - how are packets forwarded within a subnet?
>
Not germane to address allocation.  See [manet] for a lot of ideas.

> How is address
>    resolution done?
Not germane to address allocation. 

> How does a sender decide whether a destination on
You could try a route discovery.  See [manet].  Alternatively, in a future
discussion, you could explore the ramifications of whatever subnet model
is imposed on the network.

>  - How is multicast traffic distributed within the subnet?
Nobody's doing multicast.

>  - in IPv6, how are RAs distributed?
That's a topic for gateway management, and is not the first
order of business.  However I think it is interesting in the context
of [autoconf], and a lot of different ideas have been proposed.

>(or why not) is this insufficient?
Well, I think you answered your own question here.  But we don't know how
best to distribute RAs.

>decide, or has this already been decided? If the latter, where is that
The assumption is that nobody is going to impose an assumption.
But as you point out that is just an assumption, and maybe someone
will impose an assumption.  I think it would be ill-considered to do so.

I do not understand why you insist on knowing how packets
are forwarded and delivered.  If you followed [manet], you would
know that there is a lot of interesting work in progress to answer
this question.  In the meantime, people want to get some addresses.

>whether that is actually a desirable direction to go in.
I'd rather say that multicast is not the focus of the effort, and any 
multicast
semantics will be imposed for the very specific purposes of whatever is
needed or address allocation.

>this out and come up with an approach/solution?
Nothing is decided to my knowledge.

>rewritten to work over  an "ad hoc subnet"? I sure hope we aren't
I agree that a single multicast model is basically desirable, except that
some multicast groups require more maintenance than others.  For instance,
it's silly to have signaling to maintain a multicast group that every node
has to belong to.

>picture, none of this makes sense.
I totally disagree with this because:
(1) We already have credible solutions that work
(2) Your statement requires that we must all go into paralysis
(3) We need to have a "Proposed Standard" to get
       get some experience and convergence
(4) There is not today any coherent all-inclusive bigger picture
(5) Nevertheless, we are able to make a lot of sense out of
       our pieces of it.

>Which document is this? Is there just one?
There are two.  They're called OLSRv2 and DYMO.  They have different
applicability statements.  This is according to the [manet] charter.

>definition of the abstract service an "ad hoc subnet" provides?
IP is not a "service".  It's a way to establish network connectivity.
Current proposals focus on unicast.  I do not see that anyone is
suggesting that we should allocate multicast addresses as part of
the work chartered for [autoconf].  We want one way to dynamically
allocate IP addresses in ad hoc networks.   We currently have many
ways.

Regards,
Charlie P.

---

From: Pekka Savola <[email-masked]>
Date: Fri, 7 Oct 2005 19:22:29 +0300 (EEST)

> Not germane to address allocation.

It seems to be.  IPv6 uses link-local addresses, with are.. well.. 
link-local.  This stuff needs to exist -- it's not necessary to 
specify it in autoconf, but it needs to be specified.

In any case, it would be good to specify which documents you're 
talking about [manet] or [autoconf] doesn't help those who haven't 
participated in manetautoconf.  The web page for the WG/BOF 
effort (from the last proceedings) doesn't work anymore either, and I 
only found the new one by googling.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

---

From: "James Kempf" <[email-masked]>
Date: Fri, 7 Oct 2005 10:32:40 -0700

It seems to me that one of the problems might be that MANET defines a 
routing architecture which is not based on subnets. If a MANET is in 
isolation, this isn't so much of a problem, because the MANET routing 
protocol takes care of forwarding. However, autoconf is proposing to connect 
two differently architected networks, the IP subnet routed style and a 
MANET. So the questions I understand Thomas to be asking (coming from the 
Internet side) are what is the "gearing"  for the "transmission" between 
these two based on IP subnet routing, while the responses I hear Charlie 
giving are that there is some empirical evidence that certain kinds of 
"gearing" work well and they would like standardize those.

Have I got that right?

            jak

---

From: Ralph Droms <[email-masked]>
Date: Fri, 07 Oct 2005 21:19:47 -0400

> getting the devices to communicate.

Unless we have a common, well-defined, clear and written description of
the model of MANET operation, we can't have a constructive conversation
about any aspects of MANET, such as address assignment.

We can have, if you'll excuse the pun, an ad hoc discussion about the
MANET experiments that have been conducted to date.  The purpose of
research is to develop understanding, concepts and abstractions.
Without a written description of those results, we can't make any
forward progress.

> of the ad hoc network, but this is only one possible model.

It appears we may not even have a common vocabulary or understanding to
start from.  Perhaps Thomas asked an irrelevant or nonsensical (in the
sense of "not making sense in the context of MANET") question.  Without
a common set of abstractions, we have no way to talk about the
particular problem of address assignment...

> Not germane to address allocation.  See [manet] for a lot of ideas.

What is "[manet]"?

> Not germane to address allocation. 

Sorry, you've lost me here.  How can address resolution not be germane
to address assignment?

> of [autoconf], and a lot of different ideas have been proposed.

And what is [autoconf]?

> will impose an assumption.  I think it would be ill-considered to do so.

Sorry, now I'm lost...seems the conversation is (here's that bad pun
again) way too ad hoc for me.

> this question.  In the meantime, people want to get some addresses.

OK, so let me try getting at this model issue another way.  Where is the
line drawn above which there are no changes to the TCP/IP protocol
model?  Is an application that uses TCP and UDP aware that it's running
on a MANET?  Does UDP run under different rules in a MANET?  Does a
MANET provide Ethernet emulation so there are no changes to IP?

> (5) Nevertheless, we are able to make a lot of sense out of

Who is "we" and how does someone who is not "we" come to an
understanding of "our pieces of it"?

> allocate IP addresses in ad hoc networks.   We currently have many

IP is a lot more than establishing connectivity.  IP is an unreliable,
host-to-host data delivery service.

We have to know if multicast is available to know how to make existing
address assignment mechanisms work.

- Ralph

---

From: "Charles E. Perkins" <[email-masked]>
Date: Sat, 08 Oct 2005 19:58:03 +0300

Hello Ralph,

Here are some answers to your questions.

>about any aspects of MANET, such as address assignment.
You should tune in to [manet] (== the MANET working group).
It would help understand a lot.  I really don't think it is likely that
one could really understand the point of [autoconf] (== the proposed
address autoconfiguration working group) unless that person could
understand the point of [manet].

You could try looking at the working group page, RFC 2501, and
some of the proposed routing protocols.

I never saw "a common, well-defined, clear and written description of
the model of INTERNET operation" so I think you are setting the bar
way too high. But you should at least understand that people that have
been working on ad hoc networks for many years are not totally misguided,
even if you are not familiar with the work.

>Without a written description of those results, we can't make any
Again, I think you are setting the bar way too high.

It might be interesting to put such a document on the charter
of the [manet] working group.  Then it could be referenced and
used by the (proposed) new working group.

>start from. 
That could well be.

> Perhaps Thomas asked an irrelevant or nonsensical (in the
Well, the people proposing the working group have a way to talk about it.
A lot of the ideas have been documented in papers.  There are many
papers you could look at.

>Sorry, you've lost me here.  How can address resolution not be germane
Quite easily.  I can have one method for address assignment, and
a _totally_ unrelated method for address resolution.

For instance, one could design entirely new packets to replace
the current ARP packets.

I stand by my statement, to the point of considering it
almost intuitively obvious.

>again) way too ad hoc for me.
I'm not sure if I am supposed to try to respond to this.
Is it hard for you to imagine a network where the subnet
model is not imposed?  What about a flat network?

>model?
As far as I understand your question, there are no changes to the TCP/IP 
protocol
model whatsoever.  But that model does not necessarily require subnets.

>  Is an application that uses TCP and UDP aware that it's running
>on a MANET?
>
No

>  Does UDP run under different rules in a MANET?
>
No.

>  Does a
Opinions vary on this, but my answer would be no.  But IP is supposed to run
on stuff that isn't Ethernet.  Or, do you disagree??  If you do, then I 
don't see
how you can meaningfully participate in a discussion with people who spend
all their time working with IP over media that are _not_ precisely like 
Ethernet,
or maybe not even very much like Ethernet.

>Who is "we" 
Well, I am not really able to speak for the wide diversity of people who are
interesting in making the proposed working group, but I was characterizing
that group of people as "we".  So let's call them "twdopwaiimtpwg".  Then:

I totally disagree with Thonas Narten's quoted statement because:
(1) Twdopwaiimtpwg already have credible solutions that work
(2) His statement requires that twdopwaiimtpwg must all go into paralysis
(3) Twdopwaiimtpwg need to have a "Proposed Standard" to get
       get some experience and convergence
(4) There is not today any coherent all-inclusive bigger picture
(5) Nevertheless, twdopwaiimtpwg are able to make a lot of sense out of
       twdopwaiimtpwg's pieces of it.

>
>and how does someone who is not "we" come to an
There's a lot of work that's been done.  Again, I strongly recommend
reviewing the results to date from [manet].  If I were going to try to
understand DHCP, I wouldn't go into [dhc] and say, "Hey, how can
I understand this stuff".  !!  I might try to get to know some of the people
who _do_ understand it, and do the normal social things that people do.

>host-to-host data delivery service.
C'mon Ralph.  What do you want me to say?  Your point is leading nowhere.
I am saying it's not a service.  I guess you are too.

>address assignment mechanisms work.
I thought I already answered this point.  Briefly, I disagree, and to my 
understanding
twdopwaiimtpwg basically do not think that the existing address 
assignment mechanisms
can be made to work.  If you want to talk about multicast some more, 
then please be
clear about whether you are discussing the addressing model or the 
multicast group
maintenance operations.

Regards,
Charlie P.

---

From: "Charles E. Perkins" <[email-masked]>
Date: Sat, 08 Oct 2005 20:11:44 +0300

Hello Pekka,

> specify it in autoconf, but it needs to be specified.

Let's say you allocate addresses randomly to a lot of devices
that run IP.  Then, the address allocation doesn't have any
big hairy "model" except that we'd like to guarantee uniqueness.
After the address allocation is complete, likely as not I could
design quite a few different address resolution models, again as
long as unique assignment can be assumed.

I really think that this is an issue that's only good for digging
very deep and foul smelling ratholes.

> participated in manetautoconf.  The web page for the WG/BOF effort 
> (from the last proceedings) doesn't work anymore either, and I only 
> found the new one by googling.

I am sure that someone on this list will have a nice bibliography
handy, or I could find a number of interesting references if no
one else takes the opportunity.

Regards,
Charlie P.

---

From: "Charles E. Perkins" <[email-masked]>
Date: Sat, 08 Oct 2005 20:21:12 +0300

Hello,

James Kempf wrote:

> routing architecture which is not based on subnets.

Right.

> If a MANET is in isolation, this isn't so much of a problem, because 
> the MANET routing protocol takes care of forwarding.

Right.

> However, autoconf is proposing to connect two differently architected 
> networks, the IP subnet routed style and a MANET.

Yes, but this important issue is still subordinate to the main point of
getting an address assignment mechanism.  And if [autoconf] only
did the isolated address assignment, it would still be useful, although
not as useful.

> So the questions I understand Thomas to be asking (coming from the 
> Internet side) are what is the "gearing"  for the "transmission" 
> between these two based on IP subnet routing,

I didn't hear that question, but I can see how Thomas's issues
could be beneficially interpreted that way.

> while the responses I hear Charlie giving are that there is some 
> empirical evidence that certain kinds of "gearing" work well and they 
> would like standardize those.

I think the main point is that the Internet is supposed to be shielded
from the internal structure of the ad hoc network, so that the gearing
is more like a disengagement of the gearbox.  But that is a very general
characterization, with many particular refinements and intermediate
design points.  I think you would find general agreement on the
idea that a gateway should absolutely minimize the amount of information
about the ad hoc network that it advertises to the Internet.

> Have I got that right?

Sounds about right to me.

Regards,
Charlie P.