Subject: Re: [Ecrit] Issue 30: Summary

From: "Stastny Richard" <[email-masked]>
Date: Sat, 28 Jan 2006 18:25:32 +0100

>Thus, a simple rule that makes the visited emergency number match 
>first would seem to satisfy almost all practical considerations. This 
>requires no cooperation from the service provider.

Ok, if this is acceptable it could be a way out of this endless discussion.
I also agree with your most likely scenarios

To summarize:

1. By default, the device is set to use the home dialplan
and home emergency numbers, either directly or via
the home provider.

2. If not at home, the device get its location and also
the visited emergency numbers via some means

3. The visited emergency numbers take precendence
over the home dialling plan, if a clash occurs.
(Note: your home provider may provide you with an
escape code to override this, but then you definitely know
what you are doing - e.g. to reach 911xxx local numbers in UK
if you happen to be in the US.)

Note: this may cause some emergency calls done wrong,
but this is preferrable to missroute some real emergency calls

regards

Richard

________________________________

Von: Henning Schulzrinne [mailto:[email-masked]]
Gesendet: Sa 28.01.2006 18:03
An: Stastny Richard
Cc: [email-masked]
Betreff: Re: [Ecrit] Issue 30: Summary

I think we can simplify the problem slightly if we look at some 
plausible deployment scenarios for traveling users.

[Travel] User takes mobile device or laptop software to foreign 
country; keeps home service provider. Here, there is no concern about 
PBX dial plans and the like. Since all mobile devices and soft phones 
use en-bloc ("press send") rather than overlap dialing, there are no 
issues with prefix overlap. Thus, the only concern are if a visited 
emergency number is also serving some important, but different, 
function back home. The number of such collisions of practical 
interest seem to be small.

The reason for having a visited emergency number is user expectation: 
the "dial number seen on fire truck".

[ex-pat] The ex-pat user takes a terminal adapter or Ethernet phone 
to a foreign country, but gets service from a service provider back 
home, e.g., so that he can maintain a local number in his home 
country. (I use a German SIP provider, for example.)

The reason for having a visited emergency number is the babysitter 
problem: the babysitter won't know that the ex-pat is getting phone 
service from a different country and will dial the emergency number 
she is familiar with.

Relying on users to program their phone manually is unlikely to be 
done consistently.

Again, PBX extension collisions seem unlikely in this case as most 
phones would treat the foreign provider as its own "line", with its 
own dial plan. Overlap dialing is more of a concern here, due to the 
use of terminal adapters rather than IP phones. I suspect most users 
would rather have the babysitter get the fire department than 
worrying about messing up directory assistance (to take the Finnish 
118 example) in a far-away place.

Thus, a simple rule that makes the visited emergency number match 
first would seem to satisfy almost all practical considerations. This 
requires no cooperation from the service provider.

Henning

(more comments inline)

On Jan 26, 2006, at 4:34 AM, Stastny Richard wrote:

> 1. the device needs to know the location
>

This is not quite true. Brian has suggested DHCP, since it is likely 
local. In addition, we assume that the device, in many cases, will 
need to know its location for call routing in any event.

> 2. this will be very confusing for the users, especially
> in countries where you have a local dialing plan.

Given the cases above, I don't see this as a big issue in practice. 
Most people will never see this except on their mobile phone. Almost 
all service numbers on mobile phones are #something, so I think the 
number of non-emergency 3-digit dial strings used on mobile phones is 
minuscule. I can't remember ever dialing such a number on my mobile 
phone.

>
> So by default home emergency numbers and 112 will work
> 911 seems to have problems
>
> Even if you load the emergency numbers in the visited network
> from somewhere into the device,
> the question remains, which numbers take preference if a clash
> occurs (and we have seen that there is a number of clashes)
>
> One way out of this problem would be to establish a (currently
> not existing) global DIALING plan for VoIP devices.
>
> This would be very simple, all E.164 numbers need to be dialled
> in the international format using the "+", such as +1-234-567-8900
>
> This seems to be more nasty as it is, because users of mobile
> phones in non-US countries, say in Europe, are already used to
> store their numbers in the contact list in this format anyway
> (to be able to use their contact list anywhere) and most calls
> are made via the contact list, last calls or missed calls list
> ect anyway.
>
> This would open the whole number space for non-E164 numbers
> (service numbers) and within this number space the problem
> should be solvable, first defining 112 and 911 and then
> Other service numbers (eg escape codes for national or provider
> specific service codes)
>
> It is up to an international standards body (say ITU-T) to
> define this number space. This cannot be solved in ECRIT, although
> ECRIT may deliver input.
>
> Regards
> Richard
>

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From: Henning Schulzrinne <[email-masked]>
Date: Sat, 28 Jan 2006 13:10:27 -0500

I agree with your summary. There is no perfect solution, but I'm also  
hoping that the number of devices that only support overlap dialing  
will be decreasing over time. Even my new, but cheap Panasonic PSTN  
cordless phone now does en-bloc dialing, so that you can edit the  
number.