Subject: Re: draft-kurtis-multihoming-longprefix comments

From: "J. Noel Chiappa" <[email-masked]>
Date: Tue, 7 Jan 2003 10:18:17 -0500

> From: Kurt Erik Lindqvist <[email-masked]>

    >> I believe that a significant portion of multihomers do it because they
    >> want to obtain operator independence. They usually don't have PI
    >> addresses, but what I'd call "PA sold off as PI" or "PA advertised as
    >> PI".

First, once again, about "provider-independent addresses", AKA "connectivity-
independent addresses".

This is pretty much like asking for a street address that stays the same even
when you move.

Needless to say, try that one in the real world and see how far you get with
it.

In any rational discussion of addressing, the phrase "provider-independent
addresses" ought to receive the same reception as "location-independent
street address" - i.e. something between concern (that the person needs to be
institutionalized) and racous laughter (at the ludicrousness of it).

Look, if you want some sort of identifier for machines, one that stays the
same even when a machine moves somewhere else, the IPv4 architecture simply
does not provide it. Frankly, it wasn't even guessed at as a requirement,
back when the Internet had 18 total nets in it.

IPv6 adopted the IPv4 architecture lock, stock, and barrel, changing only the
length of the address. This is touted as its great strength - in fact, it's
its greatest weakness, and we see an example here.

If you don't like the fact that IPv6 does not have identifiers for machines,
ones that stays the same even when a machine moves, either i) complain to the
IPv6 architect(s), or ii) work with people like Ran who are trying to add one.

*Don't* come ask for "location-indepedent street addresses".

    > Well, what I am looking for is a) Any idea of why people are doing
    > this. We are again back to the problem that we should first understand
    > what we are trying to solve before we start posting solutions.

Oh, I think it's reasonably easy to understand why people want identifiers
for their machines that stay the same even if they change providers. They
want to make it easy (or at least easier) to change providers, and prevent
lock-in.

The only possible solution *in the architecture as it stands* is to use DNS
names, if people need a location-independent host identifier.

Another option, again, is to work with people like Ran who are trying to add
such a namespace.

Too bad IPv6 didn't have one from the start.

	Noel

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Tue, 7 Jan 2003 18:32:33 +0100 (CET)

> IPv6 architect(s), or ii) work with people like Ran who are trying to add one.

Do you (or Ran) have a pointer to this work?

Iljitsch

---

From: "Tony Hain" <[email-masked]>
Date: Tue, 7 Jan 2003 11:31:20 -0800

J. Noel Chiappa wrote:
> First, once again, about "provider-independent addresses", 
> AKA "connectivity- independent addresses".
> 
> This is pretty much like asking for a street address that 
> stays the same even when you move.

No, it is asking for the same address to work when USPS, UPS, FedEx, the
pizza guy ... service providers deliver the packets. Mixing the concept
of service provider and connectivity is what makes it so hard for the
average network manager to understand why his address has to change when
he changes providers. In 'the real world' the connectivity (street) is
separated from the service provider.

> 
> Needless to say, try that one in the real world and see how 
> far you get with it.

The phone system allows this (for a price), so people expect it to be
possible from the 'more powerful' Internet.

> 
> In any rational discussion of addressing, the phrase 
> "provider-independent addresses" ought to receive the same 
> reception as "location-independent street address" - i.e. 
> something between concern (that the person needs to be

Only by routing gurus. The average network manager looks at 'the real
world' where a large number of services are available using a common
street address, and the anomaly of portable numbers in the phone system,
and can't figure out why the Internet is not even capable of those
simple things.

> 
> 
> Look, if you want some sort of identifier for machines, one 
> that stays the same even when a machine moves somewhere else, 
> the IPv4 architecture simply does not provide it. Frankly, it 
> wasn't even guessed at as a requirement, back when the 
> Internet had 18 total nets in it.
> 
> IPv6 adopted the IPv4 architecture lock, stock, and barrel, 
> changing only the length of the address. This is touted as 
> its great strength - in fact, it's its greatest weakness, and 
> we see an example here.

The strength is that it is a model that people understand. Where it
breaks down is that the decision leading to PA-only occurred at the same
time as CIDR. The zeal to clean up & prevent a new swamp resulted in a
system where the multi-homing issues were pushed to the host (ie: out of
the DFZ routing space). Now that end site network managers are getting a
voice, they are pushing back and stating they don't want it in the host.

> 
> If you don't like the fact that IPv6 does not have 
> identifiers for machines, ones that stays the same even when 
> a machine moves, either i) complain to the IPv6 architect(s), 
> or ii) work with people like Ran who are trying to add one.
> 

People aren't asking for location-independent addresses, in fact they
are asking for the architectural equivalent of a street address.

> Oh, I think it's reasonably easy to understand why people 
> want identifiers for their machines that stay the same even 
> if they change providers. They want to make it easy (or at 
> least easier) to change providers, and prevent lock-in.
> 
> The only possible solution *in the architecture as it stands* 
> is to use DNS names, if people need a location-independent 
> host identifier.
> 
> Another option, again, is to work with people like Ran who 
> are trying to add such a namespace.

There are also as set of us who are trying to define an intermediate
approach that scales within the constraints of the current routing
technology while we wait for the longer term additional namespace.

Tony

---

From: Brian E Carpenter <[email-masked]>
Date: Thu, 09 Jan 2003 17:18:56 +0100

Tony Hain wrote:
...
> are asking for the architectural equivalent of a street address.

I disagree. They are asking for the equivalent of a cell phone
number, on a network that doesn't have a call setup phase.

   Brian

---

From: "Tony Hain" <[email-masked]>
Date: Thu, 9 Jan 2003 16:05:03 -0800

Brian E Carpenter wrote:
> I disagree. They are asking for the equivalent of a cell 
> phone number, on a network that doesn't have a call setup phase.

I think we are trying to get to the same place in terms of real-time
air-link portability, but current implementations of cell addresses
require changing whenever the service contractor changes. This is
clearly acceptable to the individual, even if annoying, but to the
larger entities it represents a provider lock because it becomes very
costly to change. To be specific, they want:
   an unambiguous address that will reach the device, 
   independent of carriage or contractor relationship 
   over time. 
In other words, they should be able to change or have multiple service
providers without requiring any coorelation between the address and the
provider of the transport service. I believe this is closer to a street
address than it is to a cell device.

This is the crux of the discussion here, because that goal is completely
divergent from optimizing a connectivity graph to minimize the size of
the routing table. While our task is to find soulutions that keep the
routing table at a reasonable scale, ignoring the basic requirement as
too difficult is not useful. 

Tony

---

From: Eliot Lear <[email-masked]>
Date: Thu, 09 Jan 2003 16:08:33 -0800

Tony,

Over time we still have DNS to allow for people to make changes.  This 
means that one has to work the transition such that prefixes can change 
at the convenience of the end user.

Eliot

---

From: "Tony Hain" <[email-masked]>
Date: Thu, 9 Jan 2003 17:35:03 -0800

> at the convenience of the end user.

My name does not change when I move or change cell providers, but it is
still painful and expensive to touch every place that has the name to
address mapping. Multiply that for larger enterprises, and the numbers
get big enough for budget watchers to notice. 

Also, we already see a market for email redirection, where an email
address can stay consistent over ISP changes. Clearly some people don't
want to deal with changing the mappings from their name to the locator
info if they don't have to, and large enterprises do this all the time
by registering their own names rather than taking a subdomain from the
ISP. In any case, DNS is not the only place names are translated into
addresses, so we must not base an approach on the assumption that it is.

Tony

---

From: Kurt Erik Lindqvist <[email-masked]>
Date: Fri, 10 Jan 2003 14:09:45 +0100

> This is pretty much like asking for a street address that stays the 

[..]

> back when the Internet had 18 total nets in it.

To be honest I think you are not really mirroring the full story here.

> its greatest weakness, and we see an example here.

Which is why we have this WG....

> *Don't* come ask for "location-indepedent street addresses".

I think that is one of the questions we have to ask. It might not be 
the answer, but we do need to ask the question.

> want to make it easy (or at least easier) to change providers, and 

There is two sides to this

a) Why do people multihome?
b) Why do they want PI-like address space?

What worries me is if people are doing a to get to b. I don't want to 
see these two being the same.

> names, if people need a location-independent host identifier.

There is AFAIK no limit on this group to use the architecure as it 
stands. And I don't believe DNS is the only solution.

- kurtis -

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Fri, 10 Jan 2003 15:52:48 +0100 (CET)

> see these two being the same.

People multihome because it makes their connection to the net more
reliable, because it is sometimes cheaper and because you get better
performance if interconnection between ISPs isn't very good.

People want PI space because that way changing ISPs is trivial. And even
for people who don't want to multihome this is very important: if your
ISP goes belly up, you want to be able to connect to a new one very
quickly.

In theory, renumbering isn't a big problem: you only need to change a
DHCP configuration or some prefix advertisements. In practice, it is a
nightmare because IP addresses show up in way too many places, often to
enforce access restrictions. Getting rid of this is probably the hardest
part in any multiple-address solution.

So either we have portable addresses or we create a better way to do
access restrictions.

-- 
http://shameless-book-plug.bgpexpert.com/'BGP'-by-Iljitsch-van-Beijnum/

---

From: Eliot Lear <[email-masked]>
Date: Fri, 10 Jan 2003 10:42:39 -0800

> get big enough for budget watchers to notice.

Your initial comment related to enterprises.  Enterprises don't change 
providers all that often.  But even if they did, we have the tools to 
readdress devices in IPv4 -- it's called DHCP.  It could *even* be used 
in conjunction with mobile-ip, and not just for the FA.  Thus, one uses 
one mechanism for mobility, another one for a stable identifier, and for 
that matter, perhaps a third for micromobility.  This falls under the 
classification of "the right tool for the right job".

> addresses, so we must not base an approach on the assumption that it is.

Let's back up:

   [email-masked] (for example) uses pobox.com as a place to have a 
stable identifier.  This would be no different than 
[email-masked] except that it takes some amount of work to 
maintain a server.  But even so the name remains the same.  So long as 
userspersonaldomain.com can easily determine its address, and records 
can be updated by authorized individuals, life continues.  This is 
possible.  Ralph Droms has worked on functionality such as prefix 
delegation.  Then, see above.

Can you explain to me why systems that use translation other than DNS 
aren't broken and worth fixing?

Eliot

---

From: "Tony Hain" <[email-masked]>
Date: Fri, 10 Jan 2003 17:26:32 -0800

Eliot Lear wrote:
> providers all that often.  

'Often' is a function of your perspective of time. Even if they don't
meet your definition of often, they want the ability to move at a
moments notice without the threat of a significant cost hanging over
their heads.

> But even if they did, we have the tools to 

Readdressing the nodes is not the problem. In IPv6 the RA allows a
smoother version of doing that job, because it allows both old and new.
The real problem is in finding all the places that addresses are
explicitly stored.

> maintain a server.  

The server is not the problem. This is due to the difference between a
central vs. distributed database. The user can change [email-masked] and
it happens as quickly and as often as the user wants to change it. With
a personal domain, the minimum usable time is measured in hours, and to
be completely useful, we are talking a day or two (I have first hand
experience here because Verizon changes my address a couple of times a
year, and it takes a few hours after I get the dns updated before I can
use the name). 

> But even so the name remains the same.  So long as 
> can be updated by authorized individuals, life continues. 

Eventually ...

> This is 

Because it is DNS that is broken (read that not reliable and fast) and
hasn't been fixed in 15 years. When people either can't register values
in DNS (due to lack of a scalable trust infrastructure for access to the
database), or their app can't reliably get answers back in the necessary
timeframe, they choose to build their own explicit tables. One simple
version of this is router acl's, another is SIP or multi-player game
rendezvous points. DNS does not work for all applications, therefore DNS
names can't be the solution for all multi-homing.

---

From: Kurt Erik Lindqvist <[email-masked]>
Date: Sun, 12 Jan 2003 20:15:38 +0100

> ISP goes belly up, you want to be able to connect to a new one very

Well, this is what I intuitively would say as well. However, there is 
(as you yourself noted in an earlier email) not that many people that 
multihome. There are a lot more that get PI space. I am still doubtful 
that we understand the issue.

I am leaning to the conclusion that what you want depend on what you 
are. And each will require a different solution.

In principle, a "advanced" DSL home user want to multihome for price. 
Here are multiple address solution might be the right answer.

If I am a SOHO, I am probably also after cost benefits.

If I am a on-line broker I am probably after resilience, and a routing 
solution might be what I want.

If I am IBM, I will fall under any provider category.

I think something that is very important to keep in mind is what Tony 
Li said, we need to get away from the model where when a user want's to 
multihome he will add a entry in the DFZ. The question is, does that 
apply for everyone and do we think we can get there in one single large 
evolutionary step?

I think we need to get there; we will get there; but we will have to do 
it bit by bit.

> part in any multiple-address solution.

I know of some really large re-numberings. I think most of the time, 
people are making a larger fuss of this than it is.

Best regards,

- kurtis -