Subject: Re: [Sipping] Comments on sos draft -03 (URI)

From: [email-masked]
Date: Tue, 7 Jan 2003 22:15:15 EST

In a message dated 1/7/2003 1:48:08 PM Eastern Standard Time, 
[email-masked] writes:

I don't know what you mean by 'local area'. I don't see how I can 
require Starbucks to support a PSTN gateway in each of its 802.11 hot spots.

Are you mandating that every LAN, every 802.11 hotspot, every IETF 
wireless LAN has to have:
- an outbound SIP proxy server, and
- a PSTN gateway that can dial 911
?

[MAP] No, but if a LAN, 802.11 hotspot, etc claims to be providing "telephone 
service" then it should come under the regulatory requirements and provide 
proper service, which I believe requires what I was describing. Of course, if 
someone is not claiming to provide "telephone service", then it doesn't 
matter what happens or if their "home domain" fails to properly handle an 
emergency call.

Rosen, Brian wrote:
> 
> In most US enterprises, and for that matter, in most US college
> campuses, the emergency number is 9-911.  911 would not connect

[HS] I think there are attempts to change this; see 
http://emergency.lib.uci.edu/ or 
http://www.news.cornell.edu/Chronicle/97/7.24.97/911.html or 
http://www.med.umich.edu/medschool/faculty/handbook/phones.html
for some quick Google research.

I doubt that anybody sane will assign somebody extension 911.

[MAP] I agree fully that no one should assign an extension of 911 if they can 
avoid it and private systems should allow 911 to be interpreted as a call to 
emergency, even without prefixing it with a "9", but the point is that we 
can't design SIP phones, or protocols, or proxy functioning based on an 
assumption that no one is doing this. (Incidentally, this mean that some 
hotels would have to get rid of room number 911, just as some airplanes don't 
have a row 13.)

[HS] There are probably two pragmatic approaches:

- Network-based: Don't assign 000, 08, 112, 110, 118, 119, 911 and 999 
as regular numbers. 0-00 would seem to be difficult since that's the 
common way that you'd dial an international number from a European PBX 
phone. However, it should never appear as anything but the initial part 
of an overlap dialing string, which wouldn't be in a tel: URI to begin with.
[MAP] So does this mean that none of these numbers could be used as extension 
numbers? Or hotel room numbers?

[HS] One can argue how difficult it would be to vacate the other half dozen 
numbers.

[MAP] And one must also presume that it will never happen, and accept that 
these dialing strings (or numbers starting with them) will forever exist 
somewhere in the telephony world.

Mike Pierce
Artel
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---

From: Henning Schulzrinne <[email-masked]>
Date: Wed, 08 Jan 2003 09:40:51 -0500

> matter what happens or if their "home domain" fails to properly handle an 

I have control over my home domain, so it makes sense to put more 
responsibility on it. LANs shouldn't have to provide 'telephone 
service'; things should work if they provide IP transport. That's the 
Internet approach.

> hotels would have to get rid of room number 911, just as some airplanes don't 

I agree that this isn't ideal. However, in practice, we probably will 
have two cases that may make this point moot:

- The hotel or business has its own VoIP phone system. In that case, 
with the DHCP option outlined in the 04 draft, the device can discover 
both the outbound proxy and the local emergency numbers.

- If a business has extensions, but no local SIP service (say, just a 
local wireless LAN), the issue doesn't arise, since you'd have to dial 
the E.164 number anyway. In that case, the default lists of numbers 
kicks in.

I think this covers the practically useful cases; I will change the 04 
draft to only suggest using the default list if there's no local 
knowledge. (Since, in that case, the extension problem won't appear to 
begin with.) The DHCP advertisement should advertise the local emergency 
number, but also all of the 'customary' emergency numbers that are not 
used for non-emergency uses. In other words, if a hotel in Europe 
doesn't have room 911, it should allow this as an emergency number, to 
accomodate the US or Canadian traveler.

This is not perfect for the traveler (since some of his familiar numbers 
may no longer work), but my hope is that most SIP devices will come 
equipped with an 'SOS' button which avoids the whole mess.

Henning