Subject: Re: [Iptel] Preliminary version of 2806bis 07

From: [email-masked]
Date: Tue, 3 Dec 2002 14:41:14 EST

Comments:

Nits/minor:

5.3 States that "At most one of the <isdn-subaddress> and <extension> 
parameters can appear in a tel URI." SInce this apparently means one of each, 
as indicated after the ABNF, then suggest wording the above "At most one of 
the <isdn-subaddress> and one of the <extension> parameters ..."

5.1.4 final sentence: Reword as "If it is not within the same context, it 
MUST NOT initiate the call and MUST treat the URI like an invalid 
destination."

Use of the word "prefix". Since this has a very specific meaning in E.164 (as 
noted in 7.4), several uses in 5.1.4 of this draft should be changed to avoid 
confusion as follows:

4th para starting with "There are two ways ..." in first sentence modify 
first way to read "via a full global number or any number of its leading 
digits (e.g., "=33") and ..."

6th para starting with "A global number context..." modify 2nd and 3rd 
sentences as follows: "All global numbers matching these initial digits must 
be assigned to the same organization that is describing the context and no 
such matching number can be used by any other organization. If such an 
initial string of digits does not exist, .."

7th para: change final word "prefix" to "initial set of digits".

8th para starting with "For a local number..." in final sentence about TU 
Damstadt, change "prefix" to "context".

10th para: Change begin of 1st sentence to "A context consisting of the 
initial digits of a global number does not imply ..."

------------------------------------------------------------------------------

-----------------------

Major comment:

The draft sufficiently covers the cases of global (E.164) numbers and local 
(private dialing plan) numbers. However, I continue to be concerned with the 
representation of special numbers such as 911, 411, etc as "local numbers" 
with a context made up of "+" and a country code plus possibly additional 
digits. I am not satisfied with the resolution of this issue which I began to 
raise last May on the SIPPING list. There needs to be a distinct uri format 
defined to carry these and other special dialing plan numbers which are not a 
part of the E.164 plan. They need to be handled differently than "local 
numbers", which are generally described in this draft to be the equivalent of 
private dialing plan numbers (PBX extension without direct inward dialing 
which are also not part of the E.164 numbers). These special numbers do not 
require a "context", at least, not in the same way as "local (private) 
numbers".

Consider the following:
tel:411;phone-context=+1-410-817-2000

This could be a call to 411 (local information) from the telephone number 
410-817-2000 or it could be a call to extension 411 located within the PBX 
which decided to use the context 1-410-817-2000. (Either of these is allowed 
by the draft.) The format of the tel:uri should not be such that the 
interpretation is ambiguous. I believe that SIP-ISUP interworking (recently 
approved as an RFC) would require the ability to be able to distinguish these 
two cases, since they must be mapped into ISUP differently.

Calls to 911, 411, 0, etc should not ever need a context. Their routing is 
always based on the number dialed plus information concerning the location 
(or identity) of the originator. The destination does not require a "context" 
to "verify that it is within the same context" as the call to private numbers 
do. If the "context" is intended to specify the identity of the originator, 
there are already other parameters to do this. If the "context" is intended 
to specify the area covered by the desired destination (for routing or 
verification), then it would require more than a country code (as shown in 
the example in the draft). There is no known number sequence which could 
represent what is needed for this purpose.

Definition of a 3rd format for such special numbers would include support for 
other locally dialable numbers such as #77, 0, 011 which have not been 
described.

Mike Pierce
Artel

---

From: Henning Schulzrinne <[email-masked]>
Date: Tue, 03 Dec 2002 14:46:32 -0500

tel:411 is not particularly helpful. At least with 
tel:411;phone-context=+1, somebody in Holland (or a gateway there) knows 
that this number has no local meaning.

Again, the point is that tel is an identifier. The context just makes it 
unique. For the N11 numbers, +1 will do fine, as they are logically the 
same service within NANPA. Alternatively, if they are carrier-specific, 
something like

tel:*77;phone-context=verizon.com

will do. As usual, concrete alternative suggestions are most appreciated.

> Major comment:
> 
> The draft sufficiently covers the cases of global (E.164) numbers and 
> local (private dialing plan) numbers. However, I continue to be 
> concerned with the representation of special numbers such as 911, 411, 
> etc as "local numbers" with a context made up of "+" and a country code 
> plus possibly additional digits. I am not satisfied with the resolution 
> of this issue which I began to raise last May on the SIPPING list. There 
> needs to be a distinct uri format defined to carry these and other 
> special dialing plan numbers which are not a part of the E.164 plan. 
> They need to be handled differently than "local numbers", which are 
> generally described in this draft to be the equivalent of private 
> dialing plan numbers (PBX extension without direct inward dialing which 
> are also not part of the E.164 numbers). These special numbers do not 
> This could be a call to 411 (local information) from the telephone 
> number 410-817-2000 or it could be a call to extension 411 located 
> within the PBX which decided to use the context 1-410-817-2000. (Either 
> of these is allowed by the draft.) The format of the tel:uri should not 
> be such that the interpretation is ambiguous. I believe that SIP-ISUP 
> interworking (recently approved as an RFC) would require the ability to 
> be able to distinguish these two cases, since they must be mapped into 
> ISUP differently.
> 
> Calls to 911, 411, 0, etc should not ever need a context. Their routing 
> is always based on the number dialed plus information concerning the 
> location (or identity) of the originator. The destination does not 
> require a "context" to "verify that it is within the same context" as 
> the call to private numbers do. If the "context" is intended to specify 
> the identity of the originator, there are already other parameters to do 
> this. If the "context" is intended to specify the area covered by the 
> desired destination (for routing or verification), then it would require 
> more than a country code (as shown in the example in the draft). There 
> is no known number sequence which could represent what is needed for 
> this purpose.
> 
> Definition of a 3rd format for such special numbers would include 
> support for other locally dialable numbers such as #77, 0, 011 which 
> have not been described.
> 
> Mike Pierce
> Artel
> 
> 

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---

From: Michael Hammer <[email-masked]>
Date: Tue, 03 Dec 2002 17:46:57 -0500

>tel:411;phone-context=+1-410-817-2000

This could also be a reference to my speed-dial list.  Where do we draw the 
line between route-able telephone numbers and keypresses to invoke services?

Mike H.