Subject: [RRG] Practical proposals vs. endless theoretical discussions

From: Robin Whittle <[email-masked]>
Date: Fri, 12 Sep 2008 18:33:16 +1000

Short version:   In 13 months I think the RRG has made no real
                 progress towards a meaningful recommendation for
                 scalable routing.  This is nearly 2 years after
                 RAWS and 6 months from our March 2009 deadline.

                 There are potentially practical proposals - LISP,
                 APT, Ivip, TRRP and maybe Six/One Router.  However
                 these arose independently of the RRG and are rarely
                 discussed.  Most talk is of clean-slate designs,
                 flat routing, ILNP etc. which have nothing to do
                 with our need to have something attractive to
                 end-users in the next 4 to 8 years to solve the
                 scaling problem in today's IPv4 Internet.

                 If we want to focus on clean-slate designs, we
                 should come up with either a transitional
                 scalability fix for the period we expect to
                 transpire before most networks adopt our clean
                 slate proposal - or show why no such fix is
                 really needed.  Since no-one can reasonably be
                 sure of a clean-slate approach every being widely
                 adopted, that period needs to be at least 20 years
                 and probably indefinite.

Hi Tony,

You wrote:

> |> One word: translation.
> |
> | The only translation scheme is Six/One Router, which can't work
> | for IPv4 and does not provide multihoming for packets sent from
> | hosts in non-upgraded networks.
>
> Or, ILNP with NAT.  Or, for that matter, NAT alone.

ILNP is not mentioned on the RRG wiki:

http://trac.tools.ietf.org/group/irtf/trac/wiki/RoutingResearchGroup

It is for IPv6 only, and I recall it is a radical transformation of
IPv6 which involves changes to host stacks, APIs between the stack
and applications, and to the applications themselves.  In my view
its practicality rating is indistinguishable from zero.  Does anyone
really think we could attract everyone to changing their computers
to a new kind of IPv6, when there is no benefit in them doing so
until everyone else does the same?  Also, wouldn't it require some
kind of renumbering, because it uses addresses in a very different
way?  Since we are using IPv4 now, any transition to IPv6 involves
radical renumbering anyway.

NAT doesn't give portability or multihoming.

LISP and APT were are potentially practical proposals and were both
developed about 18 to 20 months ago.  Ivip is 15 months old and TRRP
is a little younger.

Six/One Router is only for IPv6.  Maybe it could be practical too.

All these are based on the assumptions:

1 - We can't force scalable routing technologies on anyone.

2 - We need the new system to be very widely adopted by end-user
    networks large and small.

3 - There's no hope of widespread adoption if the system requires
    host changes, particularly if the benefits only accrue to
    communications between two upgraded hosts.

All but Six/One Router are based on the further assumption that in
order to be adopted widely, the system must provide full portability
and multihoming benefits for packets sent from hosts in non-upgraded
networks.  LISP didn't have that until last year.  APT has some
arrangement for this, which I think would work better if there was
only one global "APT island".  TRRP has some kind of support for
this too.

NAT has no role in a scalable routing solution, unless you mean some
kind of NAT and mapping system.  I don't understand what such an
approach is - I could never understand LISP-NAT:

http://tools.ietf.org/html/draft-lewis-lisp-interworking-01#section-6

See also the end of: http://www.firstpr.com.au/ip/ivip/lisp-links/

I have been proposing practical solutions since June 2007.  They
don't get much discussion here.  The two recent additions concern
forwarding packets to (IPv4) or towards (IPv6) using bits in the
existing header.

  ETR Address Forwarding (EAF) - for IPv4
  http://tools.ietf.org/html/draft-whittle-ivip4-etr-addr-forw-01

  Prefix Label Forwarding (PLF) - for IPv6
  http://www.firstpr.com.au/ip/ivip/ivip6/

The gotcha is the DFZ routers need an upgrade, but that may well be
practical in the time-frame available.  Both these techniques are a
major advance on map-encap due to there being no packet overhead or
PMTUD problems.  They are also a lot less complex than Translation.
 Apart from some helpful messages from Brian Carpenter regarding the
IPv6 Forwarding proposal, there has been no discussion of these at all.

Instead, month after month, there is lots of chat about theoretical
aspects of routing and potential Internet architecture which are
clean-slate designs, or involve host changes, which makes them about
as unlikely to ever be adopted as a clean slate design.

The RRG has achieved little meaningful consensus and has not been
supporting discussion of potentially practical proposals.  I think
the recent vote on "renumbering" is meaningless, since recent messages

  http://psg.com/lists/rrg/2008/msg02440.html
  http://psg.com/lists/rrg/2008/msg02441.html

indicate that different people had differing understandings of what
they were voting for.

The consensus on mapping granularity being to an identifier level
condemns the mapping system and the FIBs and RIBs of ITRs in any
RRG-supported IPv6 scheme to handle bloated 128 bit addresses.
Ivip's granularity will be /64 - which meets all practical
requirements without overly burdening the ITRs or the mapping system.

Both these consensus items seem to involve elevating something which
is merely desirable to the status of being absolutely required in
any proposal the RRG would consider - without proper regard to the
practical consequences of such requirements.

If that is "architecture" - leaving some other mob of "engineers" to
sort out the implementation details - then it is an isolated and
irrelevant view of architecture which we should avoid like the plague.

Both consensus items paint the RRG into a corner where there is no
practical solution - though for the mapping resolution, the "host
identifier" consensus is practical for IPv4.

As the months go on I see no meaningful progress in what the RRG
agrees to and I think there is far too little discussion of
potentially practical proposals.

We haven't even developed consensus on a time-frame, or multiple
possible time-frames, for when a scalable routing system would have
to be deployed and gaining wide acceptance.

It is nearly two years since RAWS and 6 months before the RRG is
supposed to report its recommendations.

I think the proposals - LISP, APT, Ivip, TRRP and Six/One Router are
the primary progress which has been achieved - but this has been
independent of the RRG itself.

I don't think the RRG has made any significant progress in
discussions or in consensus items, unless it is to be assumed the
solution lies in a clean-slate approach.   The outlook for clean
slate approaches is bleak.  IT systems are very hard to change - and
the IPv4 Internet is the world's biggest and most significant IT
system, with no clean upgrade path to anything else - including to
IPv6, which is a separate Internet.

If the RRG is to contemplate only clean-slate designs, I think we
should first come up with a plan for how the Net is going to get
along without a scalable routing solution for the period until we
are confident the clean-slate design would be very widely adopted.

Since we can't reasonably be confident of widespread adoption of
IPv6, much less a clean-slate design, that time period would be
indefinite.  So I suggest that if we want to talk about clean-slate
designs, or IPv6-based approaches with radical changes involving
host stacks and/or applications, then we must first either:

1 - Come up with a scalable routing solution for the Internet as
    it really exists today - IPv4 - which will last indefinitely.

or

2 - Show why one is not needed: prove the problems discussed at
    RAWS and which prompted the RRG's current work to be not worth
    fixing for some indefinite period while we or our successors
    develop a clean slate proposal.

Dino wrote in July:  http://psg.com/lists/rrg/2008/msg01971.html

   Well, one thing this list keeps doing is trying to draw the line
   where architecture should stop leaving it for some other process,
   say engineering, to make the really hard decisions. If the
   architecture is too high-level and doesn't "draw a line in the
   sand", then the practical architecture will happen after this
   step in the process.

   So you can't punt very many things or you become irrelevant.

I think the focus on so-called architectural level discussions -
avoiding the potentially practical proposals in favour of those with
greater architectural purity, but zero chance of adoption - is
avoiding the difficult practical matters in favour of an
interesting, but ultimately irrelevant, discussion.

 - Robin

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---

From: RJ Atkinson <[email-masked]>
Date: Fri, 12 Sep 2008 09:16:44 -0400

Earlier, Robin Whittle said:
% Most talk is of clean-slate designs, flat routing, ILNP etc.
% which have nothing to do with our need to have something
% attractive to end-users in the next 4 to 8 years to solve
% the scaling problem in today's IPv4 Internet.

Robin,

   From the quoted text above, and other even less correct
text later in your recent note, I can only believe that you
haven't bothered to read the I-Ds about ILNP and haven't
reviewed the presentation made (by my colleague) at Routing RG
in Dublin.  Similarly, I can only believe you haven't bothered
to do a literature search and read the sundry published
research papers on the topic.  All of these are disappointing
in the context of an IRTF Research Group.

   As near as I can tell, every statement you have made about
ILNP is wrong.

   You would be so much more credible in your quite numerous
notes to the RG list if you would actually would read and study
topics before you make bold and incorrect assertions about them.
A large volume of notes is not an effective substitute for a
very few, short, well-written, and technically correct notes.

   Perhaps I am guilty for not having engaged in as much
"advocacy" as you have been doing, but it seems at best
negligent on your part to make the statement quoted above.

   Separately, it is utterly unrealistic to believe that the
deployed IPv4 Internet is going to accept *any* major changes
at this point.  I spend a great deal of my time talking with
users on various continents of the globe.  They have a very
consistent message that major changes to their IPv4 deployments
(e.g. site border router reconfigurations to enable any new
routing protocol or to enable any sort of new tunnelling) are
not going to happen.  The notion of "fixing IPv4", frankly,
is indeed a lost cause and we would better serve the Internet
by trying to ensure that IPv6 deployments can move to some
better architecture, whatever that might turn out to be.

   Finally, for some long while now it has seemed to me that
you confuse the concept of an "IRTF Research Group" (which
this is) with an "IETF Working Group" (which this is not).

   Research Groups are supposed to be deliberate, careful,
thorough, and are supposed to look at clean-slate architectures
in the course of their *research*.   Theoretical discussions
are explicitly within scope for any IRTF Research Group.

   By contrast, IETF WGs are developing engineering specifications
to be considered for standardisation.  Both roles are important,
but those two roles are very very different.  It seems to me that
your frustration is primarily that this RG is not a WG.  To the
extent that is correct, the issue is with one's incorrect
expectations, and is not a legitimate issue with the operation
or behaviour of the RG.

Yours,

Ran Atkinson
[email-masked]

---

From: "Flinck, Hannu (NSN - FI/Espoo)" <[email-masked]>
Date: Fri, 12 Sep 2008 16:55:40 +0300

Hello Ran

I saw the presentation of ILNP in the last meeting and I have seen your
draft as well. It would be really good to have an analysis of ILNP in
the RRG wiki similar to what there is for LISP, Six/one, Ivip, etc just
so see and document how well ILNP solves the routing scalability issue.
Multihoming, mobility and IP security is discussed in the ILNP draft,
but routing scalability is not elaborated too much.

Best regards
Hannu 

>-----Original Message-----
>From: [email-masked] [mailto:[email-masked]] On Behalf 
>Of ext RJ Atkinson
>Sent: Friday, September 12, 2008 16:17
>To: IRTF Routing RG
>Subject: [RRG] Re: Practical Proposals vs. endless theoretical 
>discussions
>
>
>% which have nothing to do with our need to have something % 
>attractive to end-users in the next 4 to 8 years to solve % 
>the scaling problem in today's IPv4 Internet.
>
>Robin,
>
>notes to the RG list if you would actually would read and 
>study topics before you make bold and incorrect assertions about them.
>consistent message that major changes to their IPv4 
>deployments (e.g. site border router reconfigurations to 
>enable any new routing protocol or to enable any sort of new 
>tunnelling) are not going to happen.  The notion of "fixing 
>IPv4", frankly, is indeed a lost cause and we would better 
>serve the Internet by trying to ensure that IPv6 deployments 
>can move to some better architecture, whatever that might turn 
>out to be.
>
>   By contrast, IETF WGs are developing engineering 
>specifications to be considered for standardisation.  Both 
>roles are important, but those two roles are very very 
>different.  It seems to me that your frustration is primarily 
>that this RG is not a WG.  To the extent that is correct, the 
>issue is with one's incorrect expectations, and is not a 
>legitimate issue with the operation or behaviour of the RG.
>
>Yours,
>
>Ran Atkinson
>[email-masked]
>
>
>
>--

---

From: Robin Whittle <[email-masked]>
Date: Mon, 15 Sep 2008 21:13:10 +1000

Hi Ran,

> % the scaling problem in today's IPv4 Internet.

I responded to the ILNP-specific parts of your message in a separate
thread.

> topics before you make bold and incorrect assertions about them.

This is a broad-brush condemnation of my efforts, apparently
extrapolating from your disappointment with my perceived
misunderstanding of your own proposal.  I think it is bad form to
make such accusations on a mailing list without providing suitable
evidence.  You don't bother to correct my apparent misunderstanding
- your complaint would be more credible and useful if you did.

I think I do a pretty good job of contributing to progress in
scalable routing, even ignoring my own proposal.  My critiques of
APT and Six-One Router have been welcomed by the designers of these
proposals.  The current Six/One Router proposal was prompted in part
by my critique of the initial version.  I understand that my
suggestion that there be only one APT island is being considered.

I have similarly made extensive critiques of LISP - for instance of
the long-path problem of LISP-ALT - which other people have
concurred with.

You also assert that I don't read the documents of proposals I
discuss.  I most certainly do.

I didn't read your documents in detail because your proposal
involves host changes, and because it only provides benefits when
both hosts are upgraded.  In my view, this makes your proposal a
non-starter in the time-frame within which I think we need to
provide a solution, such as 4 to 8 years.

LISP with PTRs or Ivip are both vastly better than your proposal in
these regards - they don't require host changes and they can provide
multihoming and portability for packets sent by ordinary hosts in
non-upgraded networks.  APT can in principle do the same - although
I think would be best if there was only one APT island.
Furthermore, these can work with IPv4 and IPv6, while ILNP is IPv6-only

> very few, short, well-written, and technically correct notes.

I reckon my signal to noise ratio on this list is pretty high.  As
long as that is the case, I don't have to apologise for the quantity
of the signal, since it is provided without charge.  As for writing
longer messages than most folks, that is better than writing the
same material in a bunch of shorter messages.

To me, constructive critiques of of actual proposals is a very
important form of progress - however, for many months, maybe since
the end of last year, I can't remember, all such discussions have
been out of scope on this list.  I and others persist, since there
is nowhere else to discuss these things, but we are sometimes told
off for "discussing proposals":

  http://psg.com/lists/rrg/2008/msg01285.html

and when I complain about these restrictions, I am told that is out
of scope too:

  http://psg.com/lists/rrg/2008/msg01864.html

I reject suggestions such as you once made to me on the list that I
should ignore engineering details and focus on "architecture".  One
without the other is useless.  This is Internet scalable routing, so
one should expect a lot of detail in most meaningful discussions.

> % the scaling problem in today's IPv4 Internet.

I stand by this - as long as it is assumed we need to solve the
routing scaling problem in IPv4, or whatever problem arises in IPv6,
within 8 years.

Do you think we have more time than this?  If we do, then that makes
it easier to introduce my Forwarding approaches, since over a that
time-scale it would probably be quite practical to upgrade those
current routers which would still be in service in 2016, and to have
the new capabilities built into new routers.

If you think we need the new solution to be widely adopted in 8
years or less, do you seriously suggest that ILNP could be that
solution?  You would have to convince everyone to move to a new kind
of IPv6.  There are (I guess) a billion end-users.  IPv4 is the
world's greatest IT system and people use it because everyone else
uses it.  IPv6 isn't much use to most people until everyone else is
using it - so I can't see how you can assume you can change the
whole world over to IPv6 inside 8 years.

> at this point.

I don't think it is unrealistic at all.  The routers are being
replaced every 4 to 6 years or so.  LISP, APT, Ivip, TRRP etc. don't
require host changes.

> I spend a great deal of my time talking with

Sure, but there's no way they can sell an IPv6-only service to most
end-users, because it has no value, since it doesn't allow them to
communicate directly with all other Internet users.

The long-held fantasy of IPv6 proponents is that their imaginary
IPv6 egg will transform into a real IPv6 chicken, and/or their
imaginary IPv6 chicken will lay a real egg.  This magical
transformation is now supposed to happen in the real world because
networks are facing increasing pressure to use IPv4 address space
more efficiently, or because it the IPv4 DFZ routers need more RAM
and CPU power to cope with the bloating DFZ routing table.

IPv4's routing scaling problem can be solved nicely with LISP, APT,
Ivip, TRRP etc. - with a lot less expense and trouble than moving
everyone to IPv6.   These will also enable much better use of
address space.   I agree its not ideal, elegant or going to last
forever.  However, I think we are still a long way away from
applications and operating systems so fully supporting IPv6, and
from there being any real reason to adopt IPv6, that IPv6-*only*
adoption will become large enough to reduce IPv4 usage.

> are explicitly within scope for any IRTF Research Group.

I wasn't suggesting that theoretical discussions were out of scope.

What I was pointing out is that by discouraging discussion of
potentially practical proposals, the RRG has not helped much in the
development of anything which will actually be useful in the next 10
to 15 years.

I am not suggesting ILNP shouldn't be discussed.  However, I think
there needs to be some kind of agreement on a time-frame, or
multiple time-frames.

Maybe your ILNP proposal would only be practical in a very long
time-frame, like 10 or 20 years.  That's fine to discuss ILNP as if
it was practical, if we agree we have 10 or 20 years.  I think it is
a fundamentally good idea to split the address space into network
and host identifiers as you do.  Could you do a comparison between
SHIM-6, ILNP, GSE and 8+8 schemes?

If we agree we don't have as long as 10 or 20 years, then we also
need to discuss proposals which are *practical* in the conditions of
the next few years.  My complaint is that this has been sidelined.

> expectations, and is not a legitimate issue with the operation

It is not my understanding that the RRG should only consider
complete new Internet architectures.  My understanding is that we
also need to consider modifications to the current architecture of
IPv4 and IPv6.  Since we can't force anyone to adopt a new
technology, we have to make the new system firstly easy to adopt and
secondly attractive to adopt.  It is only going to solve the routing
scaling problem if the great majority of end-users adopt it.

There's no way end-users are going to abandon the Internet which
works for them and invest in an Internet which doesn't yet (and
won't for a long time) just because of any concern they might have
about the memory and CPU burdens of DFZ routers.

If this was an academic question: "Design a new scalable Internet
architecture free of constraints about backwards compatibility" then
it would be fine to ignore mere tweaks such as LISP, Ivip etc. and
the practical constraints which prompted these proposals.

However, my understanding is that there is a big problem coming up
involving the world's biggest IT system and that it is our job to
find a solution.  This involves the solution being freely adopted by
existing end-users.  For that reason, I suggest that any such
solution, such as yours, or IPv6, which involves end-users changing
their host operating systems and applications is a non-starter.
This is especially the case for IPv6 or your modified form of IPv6,
in which the average end-user would find the new system pretty
useless until such time as essentially every other end-user adopted
it as well.

  - Robin

---

From: Steven Blake <[email-masked]>
Date: Mon, 15 Sep 2008 08:43:01 -0400

> whole world over to IPv6 inside 8 years.

In five years there will be > 2 billion new cell phones with IP stacks.
How do you propose to provide global connectivity to these?

Regards,

// Steve

---

From: David Conrad <[email-masked]>
Date: Tue, 16 Sep 2008 22:17:02 -0400

Steven,

On Sep 15, 2008, at 5:43 AM, Steven Blake wrote:
>> so I can't see how you can assume you can change the

The same way global connectivity is provided to most cell phones  
today, that is, NAT.  "Global" IPv6 connectivity (to use the term  
loosely) gets you to an infinitesimal amount of content on the  
Internet.  The content most people want is available via IPv4 and  
there is no incentive for content providers to spend the money to  
change this.  At best, I suspect that within 5 years you might see  
IPv6 as an intra-ISP infrastructure through which you tunnel NAT'd  
IPv4.  In other words, the IPv4 address becomes a non-unique  
identifier over an infrastructure that uses IPv6 addresses as locators  
(with those locators numbering NAT devices (ITRs and ETRs if you  
prefer)).

Regards,
-drc