Subject: [Enum] draft-ietf-enum-unused-00.txt

From: [email-masked]
Date: Tue, 16 Jan 2007 11:32:20 -0500

There are some exposition problems with this draft that should be
addressed.  They center around the description of numbering plans and
are rather confusing to the naive reader.  For example, in section
7.2.1:

   7.2.1.  Closed Numbering Plans

   In many countries closed numbering plans are in use.  In such a
   scheme, all valid telephone numbers have a defined length - the
   number of digits used for the subscriber number is fixed.  Thus, for
   a given initial digit string, the length of the subsequent digit
   string together constituting a valid telephone number is known.  All
   other digit strings are invalid.

As I read this, it means that all E.164 nubmers for a particular
country have the same length.  E.g., in North America, a subscriber
number is 10 digits (or 11 if you count the country code).

   In these scenarios, a block of telephone numbers will be allocated to
   a service provider, and that provider will in turn assign individual
   telephone numbers for services it provides to end customers.
   Telephone numbers are of a defined length whether or not they are
   allocated or assigned.

So far, so good.

   For example, for the initial digit string "+44160649", the subsequent
   number string is three digits in length.  However, for the initial
   digit string "+44160650", the subsequent string is four digits in
   length.

At this point, I have a problem.  If one adds three digits to
"44160649" to make a number, then numbers have 11 digits.  But if one
adds four digits to "44160650", then numbers have 8 digits.

As far as I can tell, the solution to this contradiction is that
"subscriber number" refers to the digits that are after the block
prefix, and "initial digit string" refers to the digits that compose
the block prefix.

But that is not how people outside telephony think about E.164 numbers
-- to them, if you say "the number of digits used for the subscriber
number is fixed", they think you mean that all numbers in the country
code have the same length.  If you are using "subscriber number" in
this specialized way, make sure that you clearly define it as such
before using it.  (There is no preceeding use of "subscriber number"
in the draft.)

----

In section 7.2.2, the draft says "The only restriction is that all
these initial digit patterns representing telephone numbers are
unique."  I think this means "The only restriction is that no assigned
telephone number may be a prefix of another."

----

As far as I can tell from 7.2.2.1, under an open number plan, some
customers can be assigned prefixes, and the customer can select how
many digits are allowed after the prefix, and which of those sets of
digits are valid numbers.  That is, the customer is assigned a block
of numbers.  But 7.2.2 only speaks of assigning single numbers to
customers:  "Typically, it allocates number blocks from within this
range to providers, who will in turn assign telephone numbers to their
customers."

----

There is also the question of how this infrastructure interacts with
number portability, which leads to situations where any given range of
numbers is likely to be a mosaic of assignments to different carriers.

Dale

_______________________________________________
enum mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/enum

---

From: "Clive D.W. Feather" <[email-masked]>
Date: Wed, 17 Jan 2007 08:37:15 +0000

[email-masked] said:
> country have the same length.

No. It says that the first N digits (for some value of N which may depend
on the number) tells you how long the number is.

For example, in the UK, +442 or +447 tells you there is another 9 digits
to come, but +441 or +448 doesn't - the length depends on more digits.

> E.g., in North America, a subscriber

Apparently not. I am told that numbers beginning +109 are a digit longer.

> adds four digits to "44160650", then numbers have 8 digits.

12 digits, you mean.

> prefix, and "initial digit string" refers to the digits that compose

Right. The meaning of "block" varies - in the UK, the longest such is (I
think) +44845464N, where there are no subsequent digits if N is 7 but 2
otherwise.

> telephone number may be a prefix of another."

Right.

> digits are valid numbers.

Not just that: the customer can select which suffices are valid *and these
can be different lengths*. In other words, if I am allocated +99923456
(I use +999 because I don't know of a valid example) I can decide that
the valid numbers are:

  +999 23456 0
  +999 23456 1x
  +999 23456 2xxx
  +999 23456 4xx

> numbers is likely to be a mosaic of assignments to different carriers.

Do you mean open plans, or in general? I can't speak to open plans, but at
least in the UK portability is unrelated to number length.

-- 
Clive D.W. Feather  | Work:  <[email-masked]>   | Tel:    +44 20 8495 6138
Internet Expert     | Home:  <[email-masked]>  | Fax:    +44 870 051 9937
Demon Internet      | WWW: http://www.davros.org | Mobile: +44 7973 377646
THUS plc            |                            |

---

From: "Stastny Richard" <[email-masked]>
Date: Wed, 17 Jan 2007 10:41:56 +0100

Thank you Clive, you answered all the questions already

> least in the UK portability is unrelated to number length.

In open numbering plans everything may be variable:

If one looks at the Figure B.1/E.164 - Addressing by an ISDN Number
in Rec. E.164 Annex B.3.2, the N(S)N part of an E.164 number is
divided in the NDC (Network Destination Code) and the SN (Subscriber
Number)

The SN is further divided in a Partial Number and what?

The reminder of the SN is not named, we in Austria call it
Pilot Number.

The Partial Numbers are used for DDI (Direct Dialling In)

>From this figure one can derive the following:

A full E.164 number is the Pilot Number + the Partial Number

In closed numbering plans the SN is fixed, so the fixed length
includes the Pilot Number + the Partial Number.

In open numbering plans such as in Austria (and Germany) both
the Pilot Number and the Partial Number can be variable length

The numbering ordinance from the regulator defines the length
of the Pilot Number and is very complicated:

The NDC is between 1 and 4 digits

A Pilot Number is 5 digits
EXCEPT:
In NDCs 316, 463, 512, 662, 732, 2236, 2252, 5572 and 7242 
6 digits
in NDC 1 it is 7 digits

On request you may get more digits, up to 13 digits
in NDC 1, in all other NDC up to 14 digits (including CC)

Companies may also get shorter numbers, depending
on size of company (UNI) -1 or -2 digits

All this rules are only for Pilot numbers and
for Carriers
Any subscriber may add Partial Numbers behind the
Pilot Number (this was something we had to take over
from the old analog system)
The Operator (Carrier) does not know about the length
and structure of the Partial Numbers (= private number plan)

It is recommended the whole E.164 does not exceed
14 digits to make the number reachable internationally

Now to Number Portability (NP):

Only Pilot Numbers are portable. One cannot
port his company number with DDI to another
after retirement or leaving the company.

Additional Information:

Assume the Vienna E.164 Number +43 1 2345678-222

*43 is the CC
1 is the NDC
2345678-222 is the SN
+43 1 2345678 is the Pilot Number (portable)
222 is the Partial Number (DDI)
(Note: there may exist also an E.164
+43 1 2345678-3333

To reach the switchboard, you may dial
+43 1 2345678-0
BUT, you may also dial
+43 1 2345678

The call is terminated at the PBX and after
a time-out you fall back to the switch-board

You also fall back to the switchboard if
you under-dial or dial a non-existent partial number

All this makes a lot of fun with ENUM

Regards
Richard

> -----Original Message-----
> From: Clive D.W. Feather [mailto:[email-masked]]
> Sent: Wednesday, January 17, 2007 9:37 AM
> To: [email-masked]
> Cc: [email-masked]
> Subject: Re: [Enum] draft-ietf-enum-unused-00.txt
>

---

From: "Clive D.W. Feather" <[email-masked]>
Date: Wed, 17 Jan 2007 11:34:57 +0000

> Thank you Clive, you answered all the questions already

You're welcome.

I thought about this a bit more (during my morning commute) and I think
that the key difference is:

* In a "closed plan", end users are allocated numbers or blocks of numbers,
  but have no (direct) control over the length of these numbers.
* In an "open plan", end users are allocated prefixes and may create
  numbers of any length (subject to some overall limit) starting with those
  prefixes.

It's usual in a closed plan for numbers to be in blocks such that all
numbers in that block are the same length. For example, most of +1 is one
such block, and +442 and +447 are other such blocks. However, there is no
rule that can be written about this and adjacent numbers may be of
different lengths (ask about the UK's 0800 mess, but only after you've
bought me a drink). However, no number is a proper prefix of another.

---

From: [email-masked]
Date: Wed, 17 Jan 2007 08:23:22 -0500

From: "Clive D.W. Feather" <[email-masked]>

Actually, that's what you *want it to mean*.

What it *says* is that all numbers in the closed numbering plan (which
is presumably an attribute of the country's prefix, since the scope of
a "numbering plan" is not otherwise specified) have the same length.

That is, the UK, +44, does *not* have a closed numbering plan by the above
definition.

I've never heard of that.

   12 digits, you mean.

Oops, yes.

OK, but make sure that you state that meaning of "subscriber number"
clearly at the beginning, as it is unnatural to someone whose primary
interface with the PSTN is through dialing calls.

Perhaps I can sum up the above in a rule of thumb:  PSTN people tend
to think of the grouping of numbers into blocks as intrinsic, and are
constantly aware of where the block-prefix boundary is in a number.
Everybody else is entirely unaware that numbers are grouped into
blocks, and so any concept that hinges on the block structure must be
explicitly explained as such.

The question isn't number length, but where the DNS zones are broken.
Much current thinking assumes that the DNS zones are broken at the
block boundaries.  This makes sense if all the numbers in a block are
controlled by one carrier.  But if the numbers are controlled by
different carriers, the block may be covered by a patchwork of DNS
zones; in the worst case, each number could be a separate zone.

Dale

---

From: "Stastny Richard" <[email-masked]>
Date: Wed, 17 Jan 2007 15:06:20 +0100

First I have to say that draft-ietf-enum-unused-00 is not a
complete explanation of open an closed numbering plans and also
not one of open and closed dialing plans (which are different),
but the IANA registration of Enumservice "unused".

We tried to give only the main examples how to use "unused" in
the different numbering plans.

And I have to admit, the issue is confusing

> zones; in the worst case, each number could be a separate zone.

Exactly, and this is the preferred implementation for all "used"
numbers.

The problem with "unused" in open numbering plans (what kind of ever)
is,
that you cannot say how long a number will be as long as it is not
assigned.

And the only way out of this in open numbering plans is the usage of 
the "Closest encloser"

In closed numbering plans, either with all numbers the same length,
or with a fixed length per block/range, the best way (considering
number portability) is always to enter all numbers into the DNS.

Richard

> From: [email-masked] [mailto:[email-masked]]
> Sent: Wednesday, January 17, 2007 2:23 PM
> To: [email-masked]
>    >    number of digits used for the subscriber number is fixed.
Thus,
> for
>    >    string together constituting a valid telephone number is
known.
> All
>    Right. The meaning of "block" varies - in the UK, the longest such
is
> (I
>    > number portability, which leads to situations where any given
range
> of
>    Do you mean open plans, or in general? I can't speak to open plans,
but
> at

---

From: [email-masked]
Date: Wed, 17 Jan 2007 09:24:25 -0500

From: "Stastny Richard" <[email-masked]>

True.  But it seems that some critical issues in handling "unused"
regard interactions with numbering plans, so I think you're going to
have to explain numbering plans clearly.  You may be able to be
briefer (and so dodge having to explain some things) by describing
only open numbering plans, and their critical feature:  that numbers
not only differ in length, but they differ in length even within
allocation blocks, and are only set when a deal is reached with a
customer.

   The problem with "unused" in open numbering plans (what kind of
   ever) is, that you cannot say how long a number will be as long as
   it is not assigned.

   And the only way out of this in open numbering plans is the usage
   of the "Closest encloser"

Hmmm, has anyone implemented number portability within an open
numbering block?

Dale

---

From: "Stastny Richard" <[email-masked]>
Date: Wed, 17 Jan 2007 15:36:26 +0100

> You may be able to be

We will try to make the text more readable. Thanks for the comment.

> Hmmm, has anyone implemented number portability within an open

Of course. And as you said, the length is set if it is assigned by
the donor and it stays the same length until is unassigned (and
falls back into the pool of the donor).

Richard

> Sent: Wednesday, January 17, 2007 3:24 PM
> To: [email-masked]

---

From: "Michael Hammer \(mhammer\)" <[email-masked]>
Date: Wed, 17 Jan 2007 10:46:05 -0500

Clive,

This may be a useful resource to you:
http://www.nationalnanpa.com/index.html

One comment below.

Mike

> Sent: Wednesday, January 17, 2007 3:37 AM
> known.  All
> No. It says that the first N digits (for some value of N 
> which may depend on the number) tells you how long the number is.
> 
> For example, in the UK, +442 or +447 tells you there is 
> another 9 digits to come, but +441 or +448 doesn't - the 
> length depends on more digits.
> 

I do not believe this is a valid E.164 number.  There are no NPA
assigned starting with 0 or 1.

I suspect this is a dial string, where the 0 or 10 indicates request for
operator assistance.

[snip]

---

From: [email-masked]
Date: Wed, 17 Jan 2007 17:23:06 -0500

Apparently not. I am told that numbers beginning +109 are a 
   digit longer.

   From: "Michael Hammer \(mhammer\)" <[email-masked]>

I see from http://www.nationalnanpa.com/area_codes/index.html that the
prefixes +1 [1-9]9[0-9] are described "The 80 codes in this format,
called expansion codes, have been reserved for use during the period
when the current 10-digit NANP number format undergoes expansion."

I suspect that this means that there is a standby plan to extend the
"area code" (first three digits) to four digits, by mapping

+1 xxx yyy zzzz -> +1 x9xx yyy zzzz

This would lead to "the numbers beginning +1x9 are a digit longer".

Dale

---

From: "Michael Hammer \(mhammer\)" <[email-masked]>
Date: Thu, 18 Jan 2007 15:48:55 -0500

Dale,

Good point.  But, to be clear, the first digit after +1 will not be 0.

Area codes:  19xx, 29xx, 39xx, 49xx, 59xx, 69xx, 79xx, 89xx, 99xx

Mike 

> Sent: Wednesday, January 17, 2007 5:23 PM
> To: [email-masked]
> I see from http://www.nationalnanpa.com/area_codes/index.html 
> that the prefixes +1 [1-9]9[0-9] are described "The 80 codes 
> in this format, called expansion codes, have been reserved 
> for use during the period when the current 10-digit NANP 
> number format undergoes expansion."
> 
> I suspect that this means that there is a standby plan to 
> extend the "area code" (first three digits) to four digits, by mapping
>

---

From: "Clive D.W. Feather" <[email-masked]>
Date: Fri, 19 Jan 2007 08:31:46 +0000

> zones; in the worst case, each number could be a separate zone.

Then I think that "current thinking" will need to change. As soon as number
portability is allowed, it becomes possible for adjacent numbers to be
controlled by different carriers without restriction.

---

From: "Clive D.W. Feather" <[email-masked]>
Date: Fri, 19 Jan 2007 08:33:15 +0000

> assigned starting with 0 or 1.

I'm skeptical myself, and have asked the originator of the comment for more
information.

---

From: "Clive D.W. Feather" <[email-masked]>
Date: Fri, 19 Jan 2007 08:38:28 +0000

[email-masked] said:
> prefixes +1 [1-9]9[0-9]

You mean +1 [2-9]9[0-9].

> This would lead to "the numbers beginning +1x9 are a digit longer".

That might be the explanation, yes.

However, CNAC say on their site that the planned expansion is to:

   NXXX-XNXX-XXXX

(sic).

---

From: Otmar Lendl <[email-masked]>
Date: Fri, 19 Jan 2007 11:50:03 +0100

> However, CNAC say on their site that the planned expansion is to:

If that contigency plan ever needs to be implemented, that's going
to be an interesting change. Based on my experience in trying to enter
Austrian phone numbers into American web-forms/paper-forms/databases
which often are hardcoded to accept only (XXX) YYY ZZZZ, the
introduction of these longer numbers will have a quite significant
effect on a large number of IT systems.

That's not quite on the scale of the Y2K issue, but probably
close to what Germany went through when they changed from 
4-digit zip codes to 5-digit ones in '93.

/ol
-- 
< Otmar Lendl ([email-masked]) | nic.at Systems Engineer >

---

From: "Pfautz, Penn L, GBLAM" <[email-masked]>
Date: Fri, 19 Jan 2007 07:56:00 -0500

Yes, the most current plan is different as you indicate.
The N9X NPA codes are reserved for an earlier plan (and still are) but
the industry's most recent recommendation for expansion no longer relies
on them:

http://www.atis.org/inc/docs/finaldocs/020107029.doc

-----Original Message-----
From: Clive D.W. Feather [mailto:[email-masked]] 
Sent: Friday, January 19, 2007 3:38 AM
To: [email-masked]
Cc: [email-masked]
Subject: Re: [Enum] draft-ietf-enum-unused-00.txt

You mean +1 [2-9]9[0-9].

   NXXX-XNXX-XXXX

(sic).

-- 
Clive D.W. Feather  | Work:  <[email-masked]>   | Tel:    +44 20 8495
6138
Internet Expert     | Home:  <[email-masked]>  | Fax:    +44 870 051
9937
Demon Internet      | WWW: http://www.davros.org | Mobile: +44 7973
377646
THUS plc            |                            |

---

From: "Richard Shockey" <[email-masked]>
Date: Fri, 19 Jan 2007 10:17:24 -0500

> Sent: Friday, January 19, 2007 3:32 AM
> but at

Yep which is why that delegation on anything other than the full E.164
number is not a good idea.

Block delegation in the context of infrastructure ENUM is simply a foolish
idea if there even the remote chance that LNP will be implemented within a
national administration. If fact IMHO it's a foolish idea period. Whether
the numbering plan is fixed or variable length is irrelevant.

It would be helpful if people stopped thinking this is about the DNS, its
not. Its how carriers find points of interconnection. The DNS IMHO is only a
form of query response mechanism.

For administrative consistency it is much better that the national registry
be fully authoritative for the entire number range and probably it maintain
the entire NAPTR record set in order to create a level playing field among
competing application providers.

Again it should be noted that the Number Data Registry should be considered
a separate entity from how the data is to be distributed. I wont repeat
myself that its my ongoing belief that for carrier infrastructure routing
applications the global DNS is NOT an appropriate form of distribution.

---

From: [email-masked]
Date: Fri, 19 Jan 2007 13:07:32 -0500

From: Otmar Lendl <[email-masked]>

The NANP document says that they will need 10 years to implement the
change.

Dale

---

From: "Richard Shockey" <[email-masked]>
Date: Fri, 19 Jan 2007 13:58:13 -0500

---

From: [email-masked]
Date: Fri, 19 Jan 2007 14:22:52 -0500

From: "Richard Shockey" <[email-masked]>

   It would be helpful if people stopped thinking this is about the
   DNS, its not. Its how carriers find points of interconnection. The
   DNS IMHO is only a form of query response mechanism.

That's true, but without a defined query/reponse mechanism into an
open and public database, we aren't creating an "open standard" that
is directly usable by everybody.  So far, I haven't heard anyone
suggest any mechanism other than DNS.

Dale

---

From: "Richard Shockey" <[email-masked]>
Date: Fri, 19 Jan 2007 14:40:53 -0500

If the Carrier Routing Registry were fully authoritative for the entire
national number range then SIP Redirect could be used as well for the query
response. Slower but it would work, plus you could then use SIP
Authentication to control access. 

I just don't believe a Carrier Routing Registry should be open to the
"public".

The issues of Public vs Infrastructure ENUM are as I've said before
orthogonal.

> Sent: Friday, January 19, 2007 2:23 PM
> To: [email-masked]

---

From: Otmar Lendl <[email-masked]>
Date: Fri, 19 Jan 2007 20:58:27 +0100

> the numbering plan is fixed or variable length is irrelevant.

I fully agree with you here.  But to expand on ..

> form of query response mechanism.

it's worth noting that your first paragraph talks about "block
delegation" which sounds like DNS language and has a specific meaning there 
(i.e. NS records).

Another thing worth noting is that fact that "block provisioning" (i.e.
provisioning a whole block of number with one transaction into the
registry) does make a lot of sense in the context of I-ENUM. But that,
see above, should not be confused with what can be seen in the DNS.

> competing application providers.

Agreed again.

/ol

---

From: "Richard Shockey" <[email-masked]>
Date: Fri, 19 Jan 2007 15:47:10 -0500

> see above, should not be confused with what can be seen in the DNS.

I certainly agree and that is exactly the kind of issue PEPPERMINT can
hopefully address. The only exception to the matter is again one of LNP.
Granted the NANP is unique in that there is no service distinction between
fixed and mobile numbers it should be noted that over 85% of the 10K NPA NXX
blocks are in fact now "contaminated" ( yes the actual term of art) due to
both LNP and Pooling which in the NANPA context is a number conservation
measure requiring carriers to give back to the numbering plan unused 1K
blocks if required.

> 
> > For administrative consistency it is much better that the national
> registry be fully authoritative for the entire number range and probably
it maintain the entire NAPTR record set in order to create a level playing
field among competing application providers.
> Agreed again.

I'm glad we agree again here. The real issues of carrier interconnection in
I-ENUM really have noting to do with the DNS but the administrative policies
and procedures by which a National Numbering Registry is organized,
provisioned and ultimately distributed... the Global DNS being one of many
possible distribution methods.

---

From: lconroy <[email-masked]>
Date: Sat, 20 Jan 2007 13:22:27 +0000

Hi esteemed Co-Chair, Otmar, folks,

   I am having trouble working out what this thread has to do with  
the subject.
The authors' goal of this is to collect comments on this draft and to  
update
it to reflect those comments. We're trying to do this, but there are  
a lot of
OT posts *FOR THIS THREAD*.

The posts on NANP have clarified that it is not (or will not be) a fixed
numbering plan. Fine - I can remove the suggestion that it is, and  
apologise
for this unwarranted assumption (even if I'm not alone in that :).

The discussion on "prefix"/"initial digit string" shows that some  
folk may
misunderstand, and so that sentence needs a change.

"unused" already states that the C-o-R may be able to provision every  
ENUM
domain for which it is responsible. If there are parts of the tree  
for which
an entity is not responsible, then it is "from the Ministry of  
stating the
bleedin' obvious" that it should not try to provision entries for  
those parts.

If not all ENUM domains may be provisioned, then this may lead to  
several
NAPTRs being provisioned, as these reflect the apexes of the number  
groups
that are that CSP's responsibility. If there is total fragmentation,  
then
by definition this will require all of the ENUM domains to be  
provisioned,
or else there is no way to use ENUM. No surprise there, and I do not see
where in the unused draft it implies otherwise.

If there is to be a central DNS registry with NO delegation, then it  
will
be a matter for that registry and its customers to decide what goes  
where.
I guess that a communications service provider may still have a say  
in what
is delivered in response to queries for a telephone number for which  
that
provider is providing service. The effect is the same - the NAPTR is  
going
to be provisioned, and we are merely arguing about who runs the name  
servers.
That, IMHO, is irrelevant to the use of one NAPTR or another. In both  
cases,
I don't see what change would be needed to the unused draft.

If this is not to be DNS at all, then why the heck are we discussing  
a NAPTR
on the IETF ENUM mailing list, and what is the protocol that is to be  
defined
(i.e. what the IETF does)?

A plea: For anything unrelated to the unused draft, could folk PLEASE  
use a
different, appropriate, subject?

In some cases, it's reasonable to use a different mailing list.
IPTEL/SIPPING and Peppermint seem to be better targets for these.

all the best,
   Lawrence

On 19 Jan 2007, at 20:47, Richard Shockey wrote:
>> In response to Otmar's comments:

---

From: "Clive D.W. Feather" <[email-masked]>
Date: Mon, 22 Jan 2007 09:57:11 +0000

> bleedin' obvious" that it should not try to provision entries for  

Not so obvious.

Under the UK rules, my employer (THUS) is "rangeholder" for +44 20 7958 xxxx.
Some of the numbers in that block have been ported to C&W.

Incoming calls to those C&W numbers don't work unless we co-operate, so
there is a sense in which we, as rangeholder, are responsible for them. On
the other hand, the numbers are used by a C&W customer, so there's a sense
in which C&W are responsible.

It needs to be explicitly stated that THUS should *not* try to provision
entries for the ported numbers even though they have some responsibility.